National Emission Standards for Hazardous Air Pollutants:
Proposed Standards for Hazardous Air Pollutants for Hazardous Waste
Combustors (Phase I Final Replacement Standards and Phase II) [[pp. 21247-21296]]
[Federal Register: April 20, 2004 (Volume 69, Number 76)]
[Proposed Rules]
[Page 21247-21296]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr20ap04-26]
[[pp. 21247-21296]]
National Emission Standards for Hazardous Air Pollutants:
Proposed Standards for Hazardous Air Pollutants for Hazardous Waste
Combustors (Phase I Final Replacement Standards and Phase II)
[[Continued from page 21246]]
[[Page 21247]]
judge that a beyond-the-floor standard based on controlling the low
volatile metals in the hazardous waste feed would not be cost-effective
or otherwise appropriate. Therefore, we propose a low volatile metals
standard of 8.9 [mu]g/dscm for new sources.
F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine Gas?
We are proposing to establish standards for existing and new
incinerators that limit total chlorine emissions (hydrogen chloride and
chlorine gas, combined, reported as a chloride equivalent) to 1.5 and
0.18 ppmv, respectively. However, we are also proposing to establish
alternative risk-based standards, pursuant to CAA section 112(d)(4),
which a source could elect to comply with by in lieu of the MACT
emission standards for total chlorine. The emission limits would be
based on national exposure standards that ensure protection of public
health with an ample margin of safety. See Part Two, Section XIII for
additional details.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Total chlorine emissions from existing incinerators are limited to
77 ppmv by Sec. 63.1203(a)(6). This standard was promulgated in the
Interim Standards Rule (See 67 FR at 6796). Incinerators control
emissions of total chlorine with air pollution control equipment and/or
by controlling the feed concentration of chlorine in the hazardous
waste.
We have compliance test emissions data for most incinerators. Total
chlorine emissions range from less than 1 ppmv to 460 ppmv.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 1.5 ppmv, which considers
emissions variability. This is an emission level that the best
performing feed control sources could be expected to achieve in 99 of
100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 11%
of sources and reductions to the floor level would reduce total
chlorine emissions by 286 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of total chlorine: (1) Improved control with wet scrubbing; and (2)
control of chlorine in the hazardous waste feed.
Use of Wet Scrubbing. We evaluated a beyond-the-floor level of 0.8
ppmv based on improved wet scrubbers that would include increasing the
liquid to gas ratio, increasing the liquor pH, and replacing the
existing packing material with new more efficient packing material. We
made a conservative assumption that an improved wet scrubber will
provide 50% total chlorine control beyond the controls needed to
achieve the floor level given the low total chlorine levels at the
floor. Applying this wet scrubbing removal efficiency to the total
chlorine floor level of 1.5 ppmv leads to a beyond-the-floor level 0.8
ppmv. The national incremental annualized compliance cost for
incinerators to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $1.7 million and would
provide an incremental reduction in total chlorine emissions beyond the
MACT floor controls of 6 tons per year. We also evaluated nonair
quality health and environmental impacts and energy effects between
improved wet scrubbers and controls likely to be used to meet the floor
level. We estimate that this beyond-the-floor option would increase the
amount of waste water generated by 270 million gallons per year. The
option would also require sources to use an additional 3.2 million kW-
hours per year and 270 million gallons of water beyond the requirements
to achieve the floor level. The costs associated with these impacts are
accounted for in the national annualized compliance cost estimates.
Therefore, based on these factors and costs of approximately $0.29
million per additional ton of total chlorine removed, we are not
proposing a beyond-the-floor standard based on improved wet scrubbing.
Feed Control of Chlorine in the Hazardous Waste. We also evaluated
a beyond-the-floor level of 1.2 ppmv, which represents a 20% reduction
from the floor level. We chose a 20% reduction as a level that
represents the practicable extent that additional feedrate control of
chlorine in hazardous waste can be used and still achieve appreciable
emissions reductions. The national incremental annualized compliance
cost for incinerators to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $0.69 million and
would provide an incremental reduction in total chlorine emissions
beyond the MACT floor controls of 2.5 tons per year. Nonair quality
health and environmental impacts and energy effects were also evaluated
and are accounted for in the national annualized compliance cost
estimates. Therefore, based on these factors and costs of approximately
$0.28 million per additional ton of total chlorine removed, we are not
proposing a beyond-the-floor standard based on feed control of chlorine
in the hazardous waste.
For the reasons discussed above, we propose to establish the
emission standard for existing incinerators at 1.5 ppmv.
3. What Is the Rationale for the MACT Floor for New Sources?
Total chlorine emissions from incinerators are currently limited to
21 ppmv by Sec. 63.1203(b)(6). This standard was promulgated in the
Interim Standards Rule (See 67 FR at 6796). The MACT floor for new
sources for total chlorine would be 0.18 ppmv, which considers
emissions variability. This is an emission level that the single best
performing source identified with the SRE/Feed Approach could be
expected to achieve in 99 of 100 future tests when operating under
conditions identical to the test conditions during which the emissions
data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified similar potential beyond-the-floor techniques for
control of total chlorine for new sources: (1) Use of improved wet
scrubbers; and (2) control of chlorine in the hazardous waste feed.
Use of Wet Scrubbing. We evaluated a beyond-the-floor level of 0.1
ppmv using wet scrubbers as beyond-the-floor control for further
reductions in total chlorine emissions. We made a conservative
assumption that an improved wet scrubber will provide 50% total
chlorine reductions beyond the controls needed to achieve the floor
level given the low total chlorine levels at the floor. The incremental
annualized compliance cost for a new incinerator with an average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $0.2 million and would provide
an incremental reduction in total chlorine emissions of approximately
35 pounds per year. Nonair quality health and environmental impacts and
energy effects were also evaluated and are included in the cost
estimates. We estimate that this option would increase the amount of
wastewater generated by 50 million gallons per year and would require a
new source to use an additional 0.5 million kW-hours per year beyond
the requirements to achieve the floor level. For these reasons and
[[Page 21248]]
costs of $12 million per ton of chlorine removed, we are not proposing
a beyond-the-floor standard based on improved wet scrubbing control for
new sources.
Feed Control of Chlorine in the Hazardous Waste. We also believe
that the expense associated with a reduction in chlorine emissions
based on further control of chlorine concentrations in the hazardous
waste is not warranted. We considered a beyond-the-floor level of 0.14
ppmv, which represents a 20% reduction from the floor level. For
similar reasons discussed above for existing sources, we judge that a
beyond-the-floor standard based on controlling the chlorine in the
hazardous waste feed would not be cost-effective or otherwise
appropriate. Therefore, we propose a chlorine standard of 0.18 ppmv for
new sources.
G. What Are the Standards for Hydrocarbons and Carbon Monoxide?
Hydrocarbon and carbon monoxide standards are surrogates to control
emissions of organic hazardous air pollutants for existing and new
incinerators. The standards limit hydrocarbons and carbon monoxide
concentrations to 10 ppmv or 100 ppmv. See Sec. Sec. 63.1203(a)(5) and
(b)(5). Existing and new incinerators can elect to comply with either
the hydrocarbon limit or the carbon monoxide limit on a continuous
basis. Sources that comply with the carbon monoxide limit on a
continuous basis must also demonstrate compliance with the hydrocarbon
standard during the comprehensive performance test. However, continuous
hydrocarbon monitoring following the performance test is not required.
The rationale for these decisions are discussed in the September 1999
final rule (64 FR at 52900). We view the standards for hydrocarbons and
carbon monoxide as unaffected by the Court's vacature of the challenged
regulations in its decision of July 24, 2001. We therefore are not
proposing these standards for incinerators, but rather are mentioning
them here for the reader's convenience.
H. What Are the Standards for Destruction and Removal Efficiency?
The destruction and removal efficiency (DRE) standard is a
surrogate to control emissions of organic hazardous air pollutants
other than dioxin/furans. The standard for existing and new
incinerators requires 99.99% DRE for each principal organic hazardous
constituent, except that 99.9999% DRE is required if specified dioxin-
listed hazardous wastes are burned. See Sec. Sec. 63.1203(c). The
rationale for these decisions are discussed in the September 1999 final
rule (64 FR at 52902). We view the standards for DRE as unaffected by
the Court's vacature of the challenged regulations in its decision of
July 24, 2001. We therefore are not proposing these standards for
incinerators, but rather are mentioning them here for the reader's
convenience.
VIII. How Did EPA Determine the Proposed Emission Standards for
Hazardous Waste Burning Cement Kilns?
In this section, the basis for the proposed emission standards is
discussed. See proposed Sec. 63.1220 The proposed emission limits
apply to the kiln stack gases, in-line kiln raw mill stack gases if
combustion gases pass through the in-line raw mill, and kiln alkali
bypass stack gases if discharged through a separate stack.\90\ The
proposed standards for existing and new cement kilns that burn
hazardous waste are summarized in the table below:
---------------------------------------------------------------------------
\90\ Currently, we are not aware of any preheater/preacalciner
kiln that vents its alkali bypass gases through a separate stack.
Proposed Standards for Existing and New Cement Kilns
------------------------------------------------------------------------
Emission standard \1\
Hazardous air pollutant or -------------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan \1\........ 0.20 ng TEQ/dscm; or 0.40 ng TEQ/dscm and
control of flue gas temperature not to
exceed 400[deg]F at the inlet to the
particulate matter control device.
=============================
Particulate Matter.......... 65 mg/dscm (0.028 gr/ 13 mg/dscm (0.0058
dscf). gr/dscf).
Semivolatile metals \3\..... 4.0 x 10-4 lb/MMBtu. 6.2 x 10-5 lb/MMBtu.
Low volatile metals \3\..... 1.4 x 10-5 lb/MMBtu. 1.4 x 10-5 lb/MMBtu.
Hydrogen chloride and 110 ppmv or the 78 ppmv or the
chlorine gas \4\. alternative alternative
emission limits emission limits
under Sec. under Sec.
63.1215. 63.1215.
Hydrocarbons: kilns without 20 ppmv (or 100 ppmv Greenfield kilns: 20
bypass \5,\ \6\. carbon monoxide) ppmv (or 100 ppmv
\5\. carbon monoxide and
50 ppmv \7\
hydrocarbons). All
others: 20 ppmv (or
100 ppmv carbon
monoxide) \5\.
Hydrocarbons: kilns with No main stack 50 ppmv \7\.
bypass; main stack \6,\ \8\. standard.
Hydrocarbons: kilns with 10 ppmv (or 100 ppmv 10 ppmv (or 100 ppmv
bypass; bypass duct and carbon monoxide). carbon monoxide).
stack \5,\ \6,\ \8\.
------------------------------------------------------------------------
\1\ All emission standards are corrected to 7% oxygen, dry basis. If
there is a separate alkali bypass stack, then both the alkali bypass
and main stack emissions must be less than the emission standard.
\2\ Mercury standard is an annual limit.
\3\ Standards are expressed as mass of pollutant stack emissions
attributable to the hazardous waste per million British thermal unit
heat input of the hazardous waste.
\4\ Combined standard, reported as a chloride (Cl(-)) equivalent.
\5\ Sources that elect to comply with the carbon monoxide standard must
demonstrate compliance with the hydrocarbon standard during the
comprehensive performance test.
\6\ Hourly rolling average. Hydrocarbons reported as propane.
[[Page 21249]]
\7\ Applicable only to newly-constructed cement kilns at greenfield
sites (see 64 FR at 52885). The 50 ppmv standard is a 30-day block
average limit.
\8\ Measurement made in the bypass sampling system of any kiln (e.g.,
alkali bypass of a preheater/precalciner kiln; midkiln gas sampling
system of a long kiln).
A. What Are the Proposed Standards for Dioxin and Furan?
We are proposing to establish standards for existing and new cement
kilns that limit emissions of dioxin and furans to either 0.20 ng TEQ/
dscm or 0.40 ng TEQ/dscm and control of flue gas temperature not to
exceed 400[deg]F at the inlet to the particulate matter control device.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Dioxin and furan emissions for existing cement kilns are currently
limited by Sec. 63.1204(a)(1) to 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm
and control of flue gas temperature not to exceed 400[deg]F at the
inlet to the particulate matter control device. This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6796, February
13, 2002).
Since promulgation of the 1999 final rule, we have obtained
additional dioxin/furan emissions data. We now have compliance test
emissions data for all but one cement kiln that burns hazardous waste.
The compliance test dioxin/furan emissions in our data base range from
approximately 0.004 to 20 ng TEQ/dscm.\91\ Cement kilns control dioxin
by quenching kiln gas temperatures so that gas temperatures at the
inlet to the particulate matter control device are below the range of
optimum dioxin/furan formation.
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\91\ Even though all sources have recently demonstrated
compliance with the interim standards, the dioxin/furan data in our
data base preceded the compliance demonstration. This explains why
we have emissions data that are higher than the interim standard.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
Emissions Approach described in Part Two, Section VI.C above. The
calculated floor is 0.22 ng TEQ/dscm, which considers emissions
variability. These best performing sources controlled inlet
temperatures to the particulate matter control device from 380[deg]-
475[deg]F. Although some best performing sources had inlet temperatures
to the particulate matter control device within the optimum temperature
range (i.e., £400[deg]F) for formation of dioxin/furan, their
emissions were lower than other non-best performing sources. Our data
base shows that these other non-best performing sources, when operating
within a temperature range up to 475[deg]F, had emissions of dioxin/
furan as high as 1.2 ng TEQ/dscm. We cannot explain why some sources
emit dioxin/furan at significantly lower levels than other sources
operating at similar control device inlet temperatures. As noted
earlier, there are many uncertainties and imperfectly understood
complexities relating to dioxin/furan formation.
The data generally support the relationship between inlet
temperature to the particulate matter control device and dioxin/furan
emissions: When inlet temperatures are below the optimum range of
formation, dioxin/furan emissions are lower. However, the converse may
not hold: When inlet temperatures are within the optimum range of
formation, dioxin/furan emissions may or may not be higher (but in most
cases are higher). Moreover, we are concerned that a floor level of
0.22 ng TEQ/dscm is not replicable by all sources using temperature
control because we have emissions data from sources operating below the
optimum temperature range of dioxin/furan formation that is higher than
the calculated floor level of 0.22 ng TEQ/dscm. As a result of this
concern, we would identify the floor level as 0.22 ng TEQ/dscm or
controlling the inlet temperature to the particulate matter control
device.
Allowing a source to comply with a temperature limit alone,
however, absent a numerical dioxin/furan emission limit, is less
stringent than the current interim standard of 0.20 ng TEQ/dscm, or
0.40 ng TEQ/dscm and control of flue gas temperature not to exceed
400[deg]F at the inlet to the particulate matter control device. The
current interim standard is a regulatory limit that is relevant in
identifying the floor level because it fixes a level of performance for
the source category. Given that all sources are achieving this interim
standard and that the interim standard is judged as more stringent than
the calculated MACT floor, the dioxin/furan floor level can be no less
stringent than the current regulatory limit. We are, therefore,
proposing the dioxin/furan floor level as 0.20 ng TEQ/dscm or 0.40 ng
TEQ/dscm and control of flue gas temperature not to exceed 400[deg]F at
the inlet to the particulate matter control device. This emission level
is being achieved by all sources because it is the current required
interim standard.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated activated carbon injection as beyond-the-floor control
for further reduction of dioxin/furan emissions. Activated carbon has
been demonstrated for controlling dioxin/furans in various combustion
applications. However, currently no cement kiln that burns hazardous
waste uses activated carbon injection. We evaluated a beyond-the-floor
level of 0.10 ng TEQ/dscm, which represents a 75% reduction in dioxin/
furan emissions from the floor level. We selected this level because it
represents a level that is considered routinely achievable with
activated carbon injection. In addition, we assumed for costing
purposes that cement kilns needing activated carbon injection to
achieve the beyond-the-floor level would install the activated carbon
injection system after the existing particulate matter control device
and add a new, smaller baghouse to remove the injected carbon with the
adsorbed dioxin/furan. We chose this costing approach to address
potential concerns that injected carbon may interfere with cement kiln
dust recycling practices.
The national incremental annualized compliance cost for cement
kilns to meet this beyond-the-floor level rather than comply with the
floor controls would be approximately $21 million and would provide an
incremental reduction in dioxin/furan emissions beyond the MACT floor
controls of 3.4 grams TEQ per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between activated carbon injection and controls likely to be
used to meet the floor level. We estimate that this beyond-the-floor
option would increase the amount of solid waste \92\ generated by 7,800
tons per year and would require sources to use an additional 2.6
million kW-hours per year beyond the requirements to achieve the floor
level. The costs associated with these impacts are accounted for in the
national annualized compliance cost estimates. Therefore, based on
these factors and costs of approximately $6.2 million per additional
gram of dioxin/furan removed, we are not proposing a
[[Page 21250]]
beyond-the-floor standard based on use of activated carbon injection.
---------------------------------------------------------------------------
\92\ Under the exemption from hazardous waste status in Sec.
261.4(b)(8), cement kiln dust is not currently classified as a
hazardous waste.
---------------------------------------------------------------------------
3. What Is the Rationale for the MACT Floor for New Sources?
Dioxin and furan emissions for new cement kilns are currently
limited by Sec. 63.1204(b)(1) to either 0.20 ng TEQ/dscm or 0.40 ng
TEQ/dscm and control of flue gas temperature not to exceed 400[deg]F at
the inlet to the particulate matter control device. This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6796).
The calculated MACT floor for new sources would be 0.21 ng TEQ/
dscm, which considers emissions variability. This is an emission level
that the single best performing source identified by the Emissions
Approach could be expected to achieve in 99 of 100 future tests when
operating under conditions identical to the test conditions during
which the emissions data were obtained. As discussed for existing
sources, we are concerned that a floor level of 0.21 ng TEQ/dscm would
not be reproducible by all sources using temperature control because we
have emissions data from sources operating below the optimum
temperature range of dioxin/furan formation that is higher than the
calculated floor level of 0.21 ng TEQ/dscm. As a result of this
concern, we would identify the MACT floor as 0.21 ng TEQ/dscm or
controlling the inlet temperature to the particulate matter control
device.
Allowing a source to comply with a temperature limit alone,
however, absent a numerical dioxin/furan emission limit, is less
stringent than the current interim standard of 0.20 ng TEQ/dscm, or
0.40 ng TEQ/dscm and control of flue gas temperature not to exceed
400[deg]F at the inlet to the particulate matter control device. The
current interim standard is a regulatory limit that is relevant in
identifying the floor level because it fixes a level of performance for
new cement kilns. Given that all sources are achieving this interim
standard and that the interim standard is judged as more stringent than
the calculated MACT floor, the dioxin/furan floor level can be no less
stringent than the current regulatory limit. We are, therefore,
proposing the dioxin/furan floor level as 0.20 ng TEQ/dscm or 0.40 ng
TEQ/dscm and control of flue gas temperature not to exceed 400[deg]F at
the inlet to the particulate matter control device.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated activated carbon injection as beyond-the-floor control
for further reduction of dioxin/furan emissions. We evaluated a beyond-
the-floor level of 0.10 ng TEQ/dscm, which represents a 75% reduction
in dioxin/furan emissions from the floor level. We selected this level
because it represents a level that is considered routinely achievable
with activated carbon injection. In addition, we assumed for costing
purposes that a new cement kiln will install the activated carbon
injection system after the existing particulate matter control device
and add a new, smaller baghouse to remove the injected carbon with the
adsorbed dioxin/furan. The incremental annualized compliance cost for a
new cement kiln to meet this beyond-the-floor level, rather than comply
with the floor level, would be approximately $1.0 million and would
provide an incremental reduction in dioxin/furan emissions of
approximately 0.17 grams TEQ per year, for a cost-effectiveness of $5.8
million per gram of dioxin/furan removed. Nonair quality health and
environmental impacts and energy effects were not significant factors.
For these reasons, we are not proposing a beyond-the-floor standard
based on activated carbon injection for new cement kilns. Therefore, we
are proposing the standard as 0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm or
control of flue gas temperature not to exceed 400[deg]F at the inlet to
the particulate matter control device.
B. What Are the Proposed Standards for Mercury?
We are proposing to establish standards for existing and new cement
kilns that limit emissions of mercury to 64 and 35 [mu]g/dscm,
respectively. If we were to adopt these standards, then sources would
comply with the limit on an annual basis because the standards are
based on normal emissions data.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Mercury emissions for existing cement kilns are currently limited
to 120 [mu]g/dscm by Sec. 63.1204(a)(2).\93\ This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6796). None of
the cement kilns burning hazardous waste use a dedicated control device
to remove mercury from the gas stream; however, kilns control the feed
concentration of mercury in the hazardous waste.
---------------------------------------------------------------------------
\93\ An alternative mercury standard is available for existing
cement kilns whereby a source can elect to comply with a hazardous
waste maximum theoretical emissions concentration or MTEC of mercury
of 120 [mu]g/dscm. MTEC is a term to compare metals and chlorine
feedrates across sources of different sizes. MTEC is defined as the
metals or chlorine feedrate divided by the gas flow rate and is
expressed in units of [mu]g/dscm.
---------------------------------------------------------------------------
We have emissions data for all sources. All of these data are best
classified as from normal operations, although, as explained below,
there is a substantial range within these data. For most sources, we
have normal emissions data from more than one test campaign. The normal
mercury stack emissions in our data base range from less than 2 to 118
[mu]g/dscm. These emissions are expressed as mass of mercury (from all
feedstocks) per unit volume of stack gas.
To identify the MACT floor, we evaluated all normal emissions data
using the SRE/Feed Approach. We considered normal emissions data from
all test campaigns.\94\ For example, one source in our data base has
normal emissions data for three different testing campaigns: 1992,
1995, and 1998. Under this approach we would consider the emissions
data from the three separate years or campaigns. We believe this
approach better captures the range of average emissions for a source
than only considering the most recent normal emissions. Given that no
cement kilns burning hazardous waste use a control device which
captures mercury from the flue gas stream, for purposes of this
analysis we assumed all sources achieved a SRE of zero. The effect of
this assumption is that the sources with the lowest mercury
concentrations in the hazardous waste were identified as the best
performing sources.
---------------------------------------------------------------------------
\94\ Given that we only have normal feedrate and emissions data
for mercury for cement kilns, we do not believe it is appropriate to
establish a hazardous waste thermal emissions-based standard. We
prefer to establish emission standards under the hazardous waste
thermal emissions format using compliance test data because the
metals feedrate information from compliance tests that we use to
apportion emissions to calculate emissions attributable to hazardous
waste are more reliable than feedrate data measured during testing
under normal, typical operations.
---------------------------------------------------------------------------
The calculated floor is 64 [mu]g/dscm, which considers emissions
variability, based on a hazardous waste maximum theoretical emissions
concentration (MTEC) of 26 [mu]g/dscm. This is an emission level that
the average of the best performing sources could be expected to achieve
in 99 of 100 future tests when operating under conditions identical to
the compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 59%
of sources and would reduce mercury emissions by 0.23 tons per year. If
we were to adopt such a floor level, we are proposing that sources
comply with the limit on an annual basis because it is based on normal
emissions data. Under this approach,
[[Page 21251]]
compliance would not be based on the use of a total mercury continuous
emissions monitoring system because these monitors have not been
adequately demonstrated as a reliable compliance assurance tool at
cement kiln sources. Instead, a source would maintain compliance with
the mercury standard by establishing and complying with short-term
limits on operating parameters for pollution control equipment and
annual limits on maximum total mercury feedrate in all feedstreams.
We did not use the stack emissions data of preheater/precalciner
kilns in the floor analysis because we believe the mercury emissions
are biased low when the in-line raw mill is on-line and biased high
when the in-line raw mill is off-line. (See earlier discussion on why
we are proposing not to subcategorize hazardous waste burning cement
kilns for mercury between wet process kilns and preheater/precalciner
kilns with in-line raw mills.) For either case, we believe the normal
mercury data are not representative of average emissions and,
therefore, not appropriate to include in the floor analysis. We request
comment on this data handling decision.
In the September 1999 final rule, we acknowledged that a cement
kiln using properly designed and operated MACT control technologies,
including controlling the levels of metals in the hazardous waste, may
not be capable of achieving a given emission standard because of
mineral and process raw material contributions that might cause an
exceedance of the emission standard. To address this concern, we
promulgated a provision that allows kilns to petition for alternative
standards provided they submit site-specific information that shows raw
material hazardous air pollutant contributions to the emissions prevent
the source from complying with the emission standard even though the
kiln is using MACT control. See Sec. 63.1206(b)(10).
Today's proposed floor of 64 [mu]g/dscm, which was based on a
hazardous waste MTEC of 26 [mu]g/dscm, may likewise necessitate such an
alternative because contributions of mercury in the raw materials and
fossil fuels at some sources may cause an exceedance of the emission
standard. The Agency intends to retain a source's ability to comply
with an alternative standard, and we request comment on two approaches
to accomplish this. The first approach would be to structure the
alternative standard similar to the petitioning process used under
Sec. 63.1206(b)(10). In the case of mercury for an existing cement
kiln, MACT would be defined as a hazardous waste feedrate corresponding
to an MTEC of 26 [mu]g/dscm. If we were to adopt this approach, we
would require sources, upon approval of the petition by the
Administrator, to comply with this hazardous waste MTEC on an annual
basis because it is based on normal emissions data. Under the second
approach, we would structure the alternative standard similar to the
framework used for the alternative interim standards for mercury under
Sec. 63.1206(b)(15). The operating requirement would be an annual MTEC
not to exceed 26 [mu]g/dscm. We also request comment on whether there
are other approaches that would more appropriately provide relief to
sources that cannot achieve a total stack gas concentration standard
because of emissions attributable to raw material and nonhazardous
waste fuels.
In June 2003, the Cement Kiln Recycling Coalition (CKRC) \95\
submitted to EPA information on actual mercury concentrations in the
hazardous waste burn tanks of all 14 cement facilities for a three year
period covering 1999 to 2001. In general, the information shows the
mercury concentration (in parts per million) in the hazardous waste for
each burn tank.\96\ In total, approximately 20,000 mercury burn tank
concentration data points are included in CKRC's submission.\97\ The
data show that approximately 50% of the individual burn tank
measurements are 0.6 ppmw or less, 75% are less than 1.1 ppmw, 88% are
less than 2 ppmw, and 97% of all burn tank measurements are less than 5
ppmw. For a hypothetical wet process cement kiln that gets 50% of its
required heat input from hazardous waste, a hazardous waste with a
mercury concentration of 0.6 ppmw equates approximately to an
uncontrolled (i.e., a system removal efficiency of zero) stack gas
concentration of 24 [mu]g/dscm. This estimated stack gas concentration,
of course, does not include contributions to emissions from other
mercury-containing feedstocks including raw materials and fossil fuels.
Mercury concentrations of 1.1, 2, and 5 ppmw in the hazardous waste
equate to uncontrolled stack gas concentrations of approximately 43,
79, and 196 [mu]g/dscm.\98\
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\95\ Cement Kiln Recycling Coalition is a trade organization
that represents cement companies that burn hazardous wastes as a
fuel. CKRC also represents companies that manage and market
hazardous waste fuels used in cement kilns.
\96\ For two cement facilities, the mercury concentration data
are only available on a monthly-averaged basis.
\97\ Data from three of the facilities had a significant number
of individual measurements reported as not detectable and also had
relatively high analysis detection limits (compared to levels
achieved by other cement plants). The detection limit for most
cement kilns was typically 0.1 ppm or less. For purposes of today's
preamble discussion, the measurements from these three cement plants
are excluded from the data characterization conclusions.
\98\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 23.
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We compared the concentration of mercury in the hazardous waste
associated with the normal emissions data in our data base to the 3-
year historical burn tank concentration data to estimate whether the
normal data in our data base--the basis of today's proposed floor of 64
[mu]g/dscm--are likely to represent the high end, low end, or close to
average emissions. Mercury feed concentration information is not
available for every test condition; however, the mercury concentrations
in the hazardous waste burned by the best performing sources during the
tests that generated the normal emissions ranged from 0.1 to 0.44 ppmw.
For the best performing sources comprising the MACT pool for which we
can make a comparison, it appears that the normal concentrations in the
hazardous waste during testing represent the low end (15th percentile
or less) of average mercury concentrations. We invite comment on
whether the normal emissions data in our data base are representative
of average emissions in practice and whether evaluating the data to
identify a floor level is appropriate.
In addition, we request comment on how to identify a floor level
using the 3-year hazardous waste mercury concentration data. One
potential approach would be to establish a hazardous waste feed
concentration standard expressed in ppmw. To identify a floor level
expressed as a hazardous waste feed concentration in ppmw, we
identified and evaluated the 3-year historical burn tank concentration
data of the five best performing facilities (those sources with the
lowest mean concentration considering variability). The calculated
alternative floor level is 2.2 ppmw in the hazardous waste. To put this
in context for a hypothetical wet process cement kiln that gets 50% of
its required heat input from hazardous waste, a mercury concentration
of 2.2 ppmw in the hazardous waste equates approximately to an
uncontrolled stack gas concentration of 86 [mu]g/dscm.\99\ This
[[Page 21252]]
estimated stack gas concentration, of course, does not include
contributions to emissions from other mercury-containing feedstocks
such as raw materials and fossil fuels. If we were to adopt such an
approach, we would require sources to comply with the feed
concentration standard on a short term basis (e.g., 12 hour average).
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\99\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards'',
March 2004, Chapter 23.
---------------------------------------------------------------------------
We also invite comment on whether we should judge an annual limit
of 64 [mu]g/dscm as less stringent than either the current emission
standard of 120 [mu]g/dscm or the hazardous waste MTEC of mercury of
120 [mu]g/dscm for cement kilns (so as to avoid any backsliding from a
current level of performance achieved by all sources, and hence, the
level of minimal stringency at which EPA could calculate the MACT
floor). In order to comply with the current emission standard,
generally a source must conduct manual stack sampling to demonstrate
compliance with the mercury emission standard and then establish a
maximum mercury feedrate limit based on operations during the
performance test. Following the performance test, the source complies
with a limit on the maximum total mercury feedrate in all feedstreams
on a 12-hour rolling average (not an annual average). Alternatively, a
source can elect to comply with a hazardous waste MTEC of mercury of
120 [mu]g/dscm that would require the source to limit the mercury
feedrate in the hazardous waste on a 12-hour rolling average. The floor
level of 64 [mu]g/dscm proposed today would allow a source to feed more
variable mercury-containing feedstreams (e.g., a hazardous waste with
an mercury MTEC greater than 120 [mu]g/dscm) than the current 12-hour
rolling average because today's proposed floor level is an annual
limit. For example, we estimated a hazardous waste MTEC for each burn
tank measurement associated with the 3-year historical concentration
data submitted by CKRC. We found that approximately 5% of burn tank
measurements would exceed a hazardous waste MTEC of 120 [mu]g/dscm,
including sources upon which the proposed floor is based.\100\
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\100\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards'',
March 2004, Chapter 23.
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of mercury: (1) Activated carbon injection; (2) control of
mercury in the hazardous waste feed; and (3) control of mercury in the
raw materials and auxiliary fuels. For reasons discussed below, we are
not proposing a beyond-the-floor standard for mercury.
Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. Activated carbon has been demonstrated for controlling
mercury in several combustion applications; however, currently no
cement kiln that burns hazardous waste uses activated carbon injection.
Given this lack of experience using activated carbon injection, we made
a conservative assumption that the use of activated carbon injection
will provide 70% mercury control and evaluated a beyond-the-floor level
of 19 [mu]g/dscm. In addition, for costing purposes we assumed that
cement kilns needing activated carbon injection to achieve the beyond-
the-floor level would install the activated carbon injection system
after the existing particulate matter control device and add a new,
smaller baghouse to remove the injected carbon with the adsorbed
mercury. We chose this costing approach to address potential concerns
that injected carbon may interfere with cement kiln dust recycling
practices.
The national incremental annualized compliance cost for cement
kilns to meet this beyond-the-floor level rather than comply with the
floor controls would be approximately $16.8 million and would provide
an incremental reduction in mercury emissions beyond the MACT floor
controls of 0.41 tons per year. Nonair quality health and environmental
impacts and energy effects were evaluated to estimate the impacts
between activated carbon injection and controls likely to be used to
meet the floor level. We estimate that this beyond-the-floor option
would increase the amount of solid waste generated by 4,400 tons per
year and would require sources to use an additional 21 million kW-hours
per year beyond the requirements to achieve the floor level. The costs
associated with these impacts are accounted for in the national
annualized compliance cost estimates. Therefore, based on these factors
and costs of approximately $41 million per additional ton of mercury
removed, we are not proposing a beyond-the-floor standard based on
activated carbon injection.
Feed Control of Mercury in the Hazardous Waste. We also evaluated a
beyond-the-floor level of 51 [mu]g/dscm, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
mercury in hazardous waste (beyond feedrate control that may be
necessary to achieve the floor level) can be used and still achieve
modest emissions reductions.\101\ The national incremental annualized
compliance cost for cement kilns to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $3.7
million and would provide an incremental reduction in mercury emissions
beyond the MACT floor controls of 180 pounds per year. Nonair quality
health and environmental impacts and energy effects were also
evaluated. Therefore, based on these factors and costs of approximately
$42 million per additional ton of mercury removed, we are not proposing
a beyond-the-floor standard based on feed control of mercury in the
hazardous waste.
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\101\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume V: Emission Estimates and Engineering
Costs'', March 2004, Chapter 4.
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Feed Control of Mercury in the Raw Materials and Auxiliary Fuels.
Cement kilns could achieve a reduction in mercury emissions by
substituting a raw material containing lower levels of mercury for a
primary raw material with a higher level. We believe that this beyond-
the-floor option would be even less cost-effective than either of the
options discussed above, however. Given that sources are sited near the
supply of the primary raw material, transporting large quantities of an
alternate source of raw materials is likely to be cost-prohibitive,
especially considering the small expected emissions reductions that
would result.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of mercury would be an appropriate
control option for sources. Given that most cement kilns burning
hazardous waste also burn coal as a fuel, we considered switching to
natural gas as a potential beyond-the-floor option. We are concerned
about the availability of natural gas to all cement kilns because
natural gas pipelines are not available in all regions of the United
States. See 68 FR 1673. Moreover, even where pipelines provide access
to natural gas, supplies of natural gas may not be adequate. For
example, it is common practice in cities during winter months (or
periods of peak demand) to prioritize natural gas usage for residential
areas before industrial usage. Requiring cement kilns to switch to
natural gas would place an even greater strain on natural gas
resources. Consequently, even where pipelines exist, some sources may
not be able to use natural gas during times of limited
[[Page 21253]]
supplies. Thus, natural gas may not be a viable control option for some
sources. Therefore, we are not proposing a beyond-the-floor standard
based on limiting mercury in the raw material feed and auxiliary fuels.
For the reasons discussed above, we propose not to adopt a beyond-
the-floor standard for mercury and propose to establish the emission
standard for existing cement kilns at 64 [mu]g/dscm. If we were to
adopt such a standard, we are proposing that sources comply with the
standard on an annual basis because it is based on normal emissions
data.
3. What Is the Rationale for the MACT Floor for New Sources?
Mercury emissions from new cement kilns are currently limited to
120 [mu]g/dscm by Sec. 63.1204(b)(2). New cement kilns can comply with
an alternative mercury standard that limits the hazardous waste maximum
theoretical emissions concentration or MTEC of mercury of 120 [mu]g/
dscm. This standard was promulgated in the Interim Standards Rule (See
67 FR at 6796).
The MACT floor for new sources for mercury would be 35 [mu]g/dscm,
which considers emissions variability, based on a hazardous waste MTEC
of 5.1 [mu]g/dscm. This is an emission level that the single best
performing source identified with the SRE/Feed Approach could be
expected to achieve in 99 of 100 future tests when operating under
conditions identical to the test conditions during which the emissions
data were obtained. As for existing sources, we assumed all sources
equally achieved a SRE of zero. The effect of this assumption is that
the single source with the lowest mercury concentration in the
hazardous waste was identified as the best performing source. We also
invite comment on whether we should judge an annual limit of 35 [mu]g/
dscm as less stringent than either the current emission standard of 120
[mu]g/dscm or the hazardous waste MTEC of mercury of 120 [mu]g/dscm for
cement kilns (so as to avoid any backsliding from a current level of
performance achieved by all sources).
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same three potential beyond-the-floor techniques
for control of mercury: (1) Use of activated carbon; (2) control of
mercury in the hazardous waste feed; and (3) control of the mercury in
the raw materials and auxiliary fuels.
Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. We made a conservative assumption that the use of activated
carbon injection will provide 70% mercury control and evaluated a
beyond-the-floor level of 11 [mu]g/dscm. The incremental annualized
compliance cost for a new cement kiln to meet this beyond-the-floor
level, rather than comply with the floor level, would be approximately
$1.0 million and would provide an incremental reduction in mercury
emissions of approximately 88 pounds per year. We also estimate that
this option would increase the amount of solid waste generated by 400
tons per year and would require sources to use an additional 1.9
million kW-hours per year. Nonair quality health and environmental
impacts and energy effects are accounted for in the national annualized
compliance cost estimates. Therefore, based on these factors and costs
of $23 million per ton of mercury removed, we are not proposing a
beyond-the-floor standard based on activated carbon injection for new
cement kilns.
Feed Control of Mercury in the Hazardous Waste. We also believe
that the expense for further reduction in mercury emissions based on
further control of mercury concentrations in the hazardous waste is not
warranted. A beyond-the-floor level of 28 ug/dscm, which represents a
20% reduction from the floor level, would result in little additional
mercury reductions. For similar reasons discussed above for existing
sources, we conclude that a beyond-the-floor standard based on
controlling the mercury in the hazardous waste feed would not be
justified because of the costs coupled with estimated emission
reductions.
Feed Control of Mercury in the Raw Materials and Auxiliary Fuels.
Cement kilns could achieve a reduction in mercury emissions by
substituting a raw material containing lower levels of mercury for a
primary raw material with a higher level. For a new source at an
existing cement plant, we believe that this beyond-the-floor option
would not be cost-effective due to the costs of transporting large
quantities of an alternate source of raw materials to the cement plant.
Given that the plant site already exists and sited near the source of
raw material, replacing the raw materials at the plant site with lower
mercury-containing materials would be the source's only option. For a
new cement kiln constructed at a new site--a greenfield site \102\--we
are not aware of any information and data from a source that has
undertaken or is currently located at a site whose raw materials are
low in mercury which would consistently decrease mercury emissions.
Further, we are uncertain as to what beyond-the-floor standard would be
achievable using a lower, if it exists, mercury-containing raw
material. Although we are doubtful that selecting a new plant site
based on the content of metals in the raw material is a realistic
beyond-the-floor option considering the numerous additional factors
that go into such a decision, we solicit comment on whether and what
level of a beyond-the-floor standard based on controlling the level of
mercury in the raw materials is appropriate.
---------------------------------------------------------------------------
\102\ A greenfield cement kiln is a kiln constructed at a site
where no cement kiln previously existed; however, a newly
constructed or reconstructed cement kiln at an existing site would
not be considered as a greenfield cement kiln.
---------------------------------------------------------------------------
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of mercury would be an appropriate
control option for sources. We considered using natural gas in lieu of
a fossil fuel such as coal containing higher concentrations of mercury
as a potential beyond-the-floor option. As discussed for existing
sources, we are concerned about the availability of the natural gas
infrastructure in all regions of the United States and believe that
using natural gas would not be a viable control option for all new
sources. Therefore, we are not proposing a beyond-the-floor standard
based on limiting mercury in the raw material feed and auxiliary fuels.
Therefore, we propose a mercury standard of 35 ug/dscm for new
sources. If we were to adopt such a standard, we are proposing that
sources comply with the standard on an annual basis because it is based
on normal emissions data.
C. What Are the Proposed Standards for Particulate Matter?
We are proposing to establish standards for existing and new cement
kilns that limit emissions of particulate matter to 65 mg/dscm (0.028
gr/dscf) and 13 mg/dscm (0.0058 gr/dscf), respectively.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Particulate matter emissions for existing cement kilns are
currently limited to 0.15 kilograms of particulate matter per megagram
dry feed \103\ and 20% opacity by Sec. 63.1204(a)(7). This standard
was promulgated in the Interim Standards Rule (See 67 FR at
[[Page 21254]]
6796). The particulate matter standard is a surrogate control for the
metals antimony, cobalt, manganese, nickel, and selenium in the
hazardous waste and all HAP metals in the raw materials and auxiliary
fuels which are controllable by particulate matter control. All cement
kilns control particulate matter with baghouses and electrostatic
precipitators.
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\103\ This standard equates approximately to a stack gas
concentration level of 0.030 gr/dscf for wet process kilns and 0.040
gr/dscf for preheater/precalciner kilns. The conversion varies by
process type because the amount of flue gas generated per ton of raw
material feed varies by process type.
---------------------------------------------------------------------------
We have compliance test emissions data for all cement kiln sources.
For most sources, we have compliance test emissions data from more than
one compliance test campaign. Our data base of particulate matter stack
emission concentrations range from 0.0008 to 0.063 gr/dscf.
To identify the floor level, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
Air Pollution Control Technology Approach. The calculated floor is 65
mg/dscm (0.028 gr/dscf), which considers emissions variability. This is
an emission level that the average of the best performing sources could
be expected to achieve in 99 of 100 future tests when operating under
conditions identical to the compliance test conditions during which the
emissions data were obtained. We estimate that this emission level is
being achieved by 44% of sources and would reduce particulate matter
emissions by 43 tons per year.
We are also proposing to delete the current opacity standard in
conjunction with revisions to the compliance assurance requirements for
particulate matter for cement kilns. These proposed compliance
assurance amendments include requiring a cement kiln source using a
baghouse to comply with the same bag leak detection system requirements
that are currently applicable to all other hazardous waste combustors
(see Sec. 63.1209(m)). A cement kiln source using an ESP has the
option either to (1) use a particulate matter emissions detector as a
process monitor in lieu of complying with operating parameter limits,
as we are proposing for all other hazardous waste combustor sources; or
(2) establish site-specific, enforceable operating parameter limits
that are linked to the automatic waste feed cutoff system. See Part
Three, Section III for a discussion of the proposed changes.
We also request comment on whether the particulate matter standard
should be expressed on a concentration basis (as proposed today) or on
a production-based format. A concentration-based standard is expressed
as mass of particulate matter per dry standard volume of gas (e.g., mg/
dscm as proposed today) while a production-based standard is expressed
as mass of particulate matter emitted per mass of dry raw material feed
to the kiln (e.g., the format of the interim standard). We evaluated
the compliance test production-based data associated with the most
recent test campaign to determine what the floor level would be under
this approach. The calculated floor would be 0.10 kilograms of
particulate matter per megagram dry feed. We note that a concentration
format can be viewed as penalizing more energy efficient kilns, which
burn less fuel and produce less kiln exhaust gas per megagram of dry
feed. This is because with a concentration-based standard the more
energy-efficient kilns would be restricted to a lower level of
particulate matter emitted per unit of production.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated improved particulate matter control to achieve a
beyond-the-floor standard of 32 mg/dscm (0.014 gr/dscf), which is a 50%
reduction from MACT floor emissions.\104\ For an existing source that
needs a significant reduction in particulate matter emissions, we
assumed and estimated costs for a new baghouse to achieve the beyond-
the-floor level. If little or modest emissions reductions were needed,
then improved control was costed as design, operation, and maintenance
modifications of the existing particulate matter control equipment.
---------------------------------------------------------------------------
\104\ We did not evaluate a beyond-the-floor standard based on
fuel substitution because particulate matter emissions from cement
kilns are primarily entrained raw material, not ash contributed by
the hazardous waste fuel. There is, therefore, no correlation
between particulate matter emissions and the level of ash in the
hazardous waste.
---------------------------------------------------------------------------
The national incremental annualized compliance cost for cement
kilns to meet this beyond-the-floor level rather than comply with the
floor controls would be approximately $4.8 million and would provide an
incremental reduction in particulate matter emissions beyond the MACT
floor controls of 385 tons per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between further improvements to control particulate matter and
controls likely to be used to meet the floor level. We estimate that
this beyond-the-floor option would increase the amount of solid waste
generated by 385 tons per year and would require sources to use an
additional 15 million kW-hours per year beyond the requirements to
achieve the floor level. The costs associated with these impacts are
accounted for in the national annualized compliance cost estimates.
Therefore, based on these factors and costs of approximately $12,400
per additional ton of particulate matter removed, we are not proposing
a beyond-the-floor standard based on improved particulate matter
control.
3. What Is the Rationale for the MACT Floor for New Sources?
Particulate matter emissions from new cement kilns are currently
limited to 0.15 kilograms of particulate matter per megagram dry feed
and 20% opacity by Sec. 63.1204(b)(7). This standard was promulgated
in the Interim Standards Rule (See 67 FR at 6796).
The MACT floor for new sources for particulate matter would be 13
mg/dscm (0.0058 gr/dscf), which considers emissions variability. This
is an emission level that the single best performing source identified
with the Air Pollution Control Technology Approach could be expected to
achieve in 99 of 100 future tests when operating under operating
conditions identical to the test conditions during which the emissions
data were obtained. We are also proposing to delete the current opacity
standard in conjunction with revisions to the compliance assurance
requirements for particulate matter for cement kilns. See Part Three,
Section III for details.
As discussed for existing sources, we also request comment on
whether the particulate matter standard should be expressed on a
concentration basis or on a production-based format. We evaluated the
compliance test production-based data associated with the most recent
test campaign to determine what the floor level would be under this
approach. The calculated floor would be 0.028 kilograms of particulate
matter per megagram dry feed.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated improved emissions control based on a state-of-the-art
baghouse using a high quality fabric filter bag material to achieve a
beyond-the-floor standard of 6.7 mg/dscm (0.0029 gr/dscf). This
reduction represents a 50% reduction in particulate matter emissions
from MACT floor levels. The incremental annualized compliance cost for
a new cement kiln to meet this beyond-the-floor level, rather than
comply with the floor level, would be approximately $0.38 million and
would provide an incremental reduction in particulate matter emissions
of approximately 2.6 tons per year. We estimate that this
[[Page 21255]]
beyond-the-floor option would increase the amount of solid waste
generated by less than 6 tons per year and would require sources to use
an additional 1.8 million kW-hours per year beyond the requirements to
achieve the floor level. The costs associated with these impacts are
accounted for in the national annualized compliance cost estimates.
Therefore, based on these factors and costs of approximately $61,400
per additional ton of particulate matter removed, we are not proposing
a beyond-the-floor standard based on improved particulate matter
control for new cement kilns. Therefore, we propose a particulate
matter standard of 13 mg/dscm for new sources.
D. What Are the Proposed Standards for Semivolatile Metals?
We are proposing to establish standards for existing cement kilns
that limit emissions of semivolatile metals (cadmium and lead,
combined) to 4.0 x 10-4 lbs semivolatile metals emissions
attributable to the hazardous waste per million Btu heat input of the
hazardous waste. The proposed standard for new sources is 6.2 x
10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Semivolatile metals emissions from existing cement kilns are
currently limited to 330 [mu]g/dscm by Sec. 63.1204(a)(3). This
standard was promulgated in the Interim Standards Rule (See 67 FR at
6796). Cement kilns control emissions of semivolatile metals with
baghouses or electrostatic precipitators and/or by controlling the feed
concentration of semivolatile metals in the hazardous waste.
We have compliance test emissions data for all cement kiln sources.
For most sources, we have compliance test emissions data from more than
one compliance test campaign. Semivolatile metal stack emissions range
from approximately 1 to 2,800 [mu]g/dscm. These emissions are expressed
as mass of semivolatile metals (from all feedstocks) per unit volume of
stack gas. Hazardous waste thermal emissions range from 3.0 x
10-6 to 3.7 x 10-3 lbs per million Btu. Hazardous
waste thermal emissions represent the mass of semivolatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste. Lead was the most significant contributor
to semivolatile emissions during compliance test conditions.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 4.0 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which considers
emissions variability. This is an emission level that the average of
the best performing sources could be expected to achieve in 99 of 100
future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 81%
of sources and would reduce semivolatile metals emissions by 1 ton per
year.
To put the proposed floor level in context for a hypothetical wet
process cement kiln that gets 50% of its required heat input from
hazardous waste, a thermal emissions level of 4.0 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste equates approximately to
a stack gas concentration of 180 [mu]g/dscm. This estimated stack gas
concentration does not include contributions to emission from other
semivolatile metals-containing materials such as raw materials and
fossil fuels. The additional contribution to stack emissions of
semivolatile metals in an average raw material and coal is estimated to
range as high as 20 to 50 [mu]g/dscm. Thus, for the hypothetical wet
process cement kiln the thermal emissions floor level of 4.0 x
10-4 lbs semivolatile metals attributable to the hazardous
waste per million Btu heat input of the hazardous waste is estimated to
be less than 230 [mu]g/dscm, which is less than the current interim
standard of 330 [mu]g/dscm. Given that comparing the proposed floor
level to the interim standard requires numerous assumptions (as just
illustrated) including hazardous waste fuel replacement rates, heat
input requirements per ton of clinker, concentrations of semivolatile
metals in the raw material and coal, and system removal efficiency, we
have a more detailed analysis in the background document.\105\ Our
detailed analysis indicates the proposed floor level is at least as
stringent as the interim standard (so as to avoid any backsliding from
a current level of performance achieved by all cement kilns, and hence,
the level of minimal stringency at which EPA could calculate the MACT
floor). Thus, we conclude that a dual standard--the semivolatile metals
standard as both the calculated floor level, expressed as a hazardous
waste thermal emissions level, and the current interim standard--is not
needed for this standard.
---------------------------------------------------------------------------
\105\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 23.
---------------------------------------------------------------------------
In the September 1999 final rule, we acknowledged that a cement
kiln using properly designed and operated MACT control technologies,
including controlling the levels of metals in the hazardous waste, may
not be capable of achieving a given emission standard because of
mineral and process raw material contributions that might cause an
exceedance of the emission standard. To address this concern, we
promulgated a provision that allows kilns to petition for alternative
standards provided that they submit site-specific information that
shows raw material hazardous air pollutant contributions to the
emissions prevent the source from complying with the emission standard
even though the kiln is using MACT control. See Sec. 63.1206(b)(10).
If we were to adopt the semivolatile (and low volatile) metals standard
using a thermal emissions format, then there would be no need for these
alternative standard provisions for semivolatile metals (since, as
explained earlier, that standard is based solely on semivolatile metals
contributions from hazardous waste fuels). Therefore, we would delete
the provisions of Sec. 63.1206(b)(10) as they apply to semivolatile
(and low volatile) metals. We invite comment on this approach.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of semivolatile metals: (1) Improved particulate matter
control; (2) control of semivolatile metals in the hazardous waste
feed; and (3) control of the semivolatile metals in the raw materials
and fuels. For reasons discussed below, we are not proposing a beyond-
the-floor standard for semivolatile metals.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of semivolatile metals. Our data show that all
cement kilns are already achieving greater than 98.6% system removal
efficiency for semivolatile metals, with most attaining 99.9% removal.
Thus, additional controls of particulate matter are likely to result in
only modest additional reductions of semivolatile metals emissions. We
evaluated a beyond-the-floor level of 2.0 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which
[[Page 21256]]
represents a 50% reduction in emissions from MACT floor levels. The
national incremental annualized compliance cost for cement kilns to
meet this beyond-the-floor level rather than comply with the floor
controls would be approximately $2.7 million and would provide an
incremental reduction in semivolatile metals emissions beyond the MACT
floor controls of 1.2 tons per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between further improvements to control particulate matter and
controls likely to be used to meet the floor level. We estimate that
this beyond-the-floor option would increase the amount of solid waste
generated by 300 tons per year and would also require sources to use an
additional 5.7 million kW-hours of energy per year to achieve the floor
level. The costs associated with these impacts are accounted for in the
national annualized compliance cost estimates. Therefore, based on
these factors and costs of approximately $2.3 million per additional
ton of semivolatile metals removed, we are not proposing a beyond-the-
floor standard based on improved particulate matter control.
Feed Control of Semivolatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 3.2 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
semivolatile metals in hazardous waste can be used and still achieve
appreciable emissions reductions. The national incremental annualized
compliance cost for cement kilns to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $0.30
million and would provide an incremental reduction in semivolatile
metals emissions beyond the MACT floor controls of 0.36 tons per year.
Nonair quality health and environmental impacts and energy effects were
evaluated and are included in the national compliance cost estimates.
Therefore, based on these factors and costs of approximately $0.84
million per additional ton of semivolatile metals removed, we are not
proposing a beyond-the-floor standard based on feed control of
semivolatile metals in the hazardous waste.
Feed Control of Semivolatile Metals in the Raw Materials and
Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile
metal emissions by substituting a raw material containing lower levels
of lead and/or cadmium for a primary raw material with higher levels of
these metals. We believe that this beyond-the-floor option would even
be less cost-effective than either of the options discussed above,
however. Given that cement kilns are sited near the primary raw
material supply, acquiring and transporting large quantities of an
alternate source of raw materials is likely to be cost-prohibitive.
Therefore, we are not proposing a beyond-the-floor standard based on
limiting semivolatile metals in the raw material feed. We also
considered whether fuel switching to an auxiliary fuel containing a
lower concentration of semivolatile metals would be an appropriate
control option for sources. Given that most cement kilns burning
hazardous waste also burn coal as a fuel, we considered switching to
natural gas as a potential beyond-the-floor option. For the same
reasons discussed for mercury, we judge a beyond-the-floor standard
based on fuel switching as unwarranted.
For the reasons discussed above, we propose to establish the
emission standard for existing cement kilns at 4.0 x 10-4
lbs semivolatile metals emissions attributable to the hazardous waste
per million Btu heat input of the hazardous waste.
3. What Is the Rationale for the MACT Floor for New Sources?
Semivolatile metals emissions from new cement kilns are currently
limited to 180 [mu]g/dscm by Sec. 63.1204(b)(3). This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6796).
The MACT floor for new sources for semivolatile metals would be 6.2
x 10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste,
which considers emissions variability. This is an emission level that
the single best performing source identified with the SRE/Feed Approach
could be expected to achieve in 99 of 100 future tests when operating
under conditions identical to the test conditions during which the
emissions data were obtained.
To put the proposed floor level in context for a hypothetical wet
process cement kiln that gets 50% of its required heat input from
hazardous waste, a thermal emissions level of 6.2 x 10-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste equates approximately to
a stack gas concentration of 80 [mu]g/dscm, including contributions
from typical raw materials and coal. Thus, for the hypothetical wet
process cement kiln the thermal emissions floor level of 6.2 x
10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste is
estimated to be less than the current interim standard for new sources
of 180 [mu]g/dscm.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same three potential beyond-the-floor techniques
for control of semivolatile metals: (1) Improved control of particulate
matter; (2) control of semivolatile metals in the hazardous waste feed;
and (3) control of semivolatile metals in the raw materials and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of semivolatile metals. We evaluated improved
control of particulate matter based on a state-of-the-art baghouse
using a high quality fabric filter bag material as beyond-the-floor
control for further reductions in semivolatile metals emissions. We
evaluated a beyond-the-floor level of 2.5 x 10-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste. The incremental
annualized compliance cost for a new cement kiln with an average gas
flow rate to meet this beyond-the-floor level, rather than to comply
with the floor level, would be approximately $0.38 million and would
provide an incremental reduction in semivolatile metals emissions of
approximately 144 pounds per year. Nonair quality health and
environmental impacts and energy effects were evaluated and are
included in the cost estimates. For these reasons and costs of $5.3
million per ton of semivolatile metals removed, we are not proposing a
beyond-the-floor standard based on improved particulate matter control
for new cement kilns.
Feed Control of Semivolatile Metals in the Hazardous Waste. We also
believe that the expense for further reduction in semivolatile metals
emissions based on further control of semivolatile metals
concentrations in the hazardous waste is not warranted. We also
evaluated a beyond-the-floor level of 5.0 x 10-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. Nonair quality health and environmental
impacts and energy effects were evaluated and are included in the
compliance cost estimates. For similar
[[Page 21257]]
reasons discussed above for existing sources, we conclude that a
beyond-the-floor standard based on controlling the concentration of
semivolatile metals levels in the hazardous waste feed would not be
justified because of the costs coupled with estimated emission
reductions.
Feed Control of Semivolatile Metals in the Raw Materials and
Auxiliary Fuels. Cement kilns could achieve a reduction in semivolatile
metals emissions by substituting a raw material containing lower levels
of cadmium and lead for a primary raw material with a higher level. For
a new source at an existing cement plant, we believe that this beyond-
the-floor option would not be cost-effective due to the costs of
transporting large quantities of an alternate source of raw materials
to the cement plant. Given that the plant site already exists and sited
near the source of raw material, replacing the raw materials at the
plant site with lower semivolatile metals-containing materials would be
the source's only option. For a cement kiln constructed at a new
greenfield site, we are not aware of any information and data from a
source that has undertaken or is currently located at a site whose raw
materials are inherently lower in semivolatile metals that would
consistently achieve reduced semivolatile metals emissions. Further, we
are uncertain as to what beyond-the-floor standard would be achievable
using a lower, if it exists, semivolatile metals-containing raw
material. Although we are doubtful that selecting a new plant site
based on the content of metals in the raw material is a realistic
beyond-the-floor option considering the numerous additional factors
that go into such a decision, we solicit comment on whether and what
level of a beyond-the-floor standard based on controlling the level of
semivolatile metals in the raw materials is appropriate.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of semivolatile metals would be an
appropriate control option for sources. Given that most cement kilns
burning hazardous waste also burn coal as a fuel, we considered
switching to natural gas as a potential beyond-the-floor option. For
the same reasons discussed for mercury, we judge a beyond-the-floor
standard based on fuel switching as unwarranted.
For the reasons discussed above, we propose to establish the
emission standard for new cement kilns at 6.2 x 10-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste.
E. What Are the Proposed Standards for Low Volatile Metals?
We are proposing to establish standards for existing and new cement
kilns that limit emissions of low volatile metals (arsenic, beryllium,
and chromium, combined) to 1.4 x 10-5 lbs low volatile
metals emissions attributable to the hazardous waste per million Btu
heat input of the hazardous waste.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Low volatile metals emissions from existing cement kilns are
currently limited to 56 [mu]g/dscm by Sec. 63.1204(a)(4). This
standard was promulgated in the Interim Standards Rule (see 67 FR at
6796). Cement kilns control emissions of low volatile metals with
baghouses or electrostatic precipitators and/or by controlling the feed
concentration of low volatile metals in the hazardous waste.
We have compliance test emissions data for all cement kiln sources.
For most sources, we have compliance test emissions data from more than
one compliance test campaign. Low volatile metal stack emissions range
from approximately 1 to 100 [mu]g/dscm. These emissions are expressed
as mass of low volatile metals (from all feedstocks) per unit volume of
stack gas. Hazardous waste thermal emissions range from 9.2 x
10-7 to 1.0 x 10-5 lbs per million Btu. Hazardous
waste thermal emissions represent the mass of low volatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste. For nearly every cement kiln, chromium
was the most significant contributor to low volatile emissions.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 1.4 x 10-5 lbs
low volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which considers
emissions variability. This is an emission level that the average of
the best performing sources could be expected to achieve in 99 of 100
future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 52%
of sources and would reduce low volatile metals emissions by 0.10 tons
per year.
To put the proposed floor level in context for a hypothetical wet
process cement kiln that gets 50% of its required heat input from
hazardous waste, a thermal emissions level of 1.4 x 10-5 lbs
low volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste equates approximately to
a stack gas concentration of 7 [mu]g/dscm. This estimated stack gas
concentration does not include contributions to emission from other low
volatile metals-containing materials such as raw materials and fossil
fuels. The additional contribution to stack emissions of low volatile
metals in an average raw material and coal is estimated to range from
less than 1 to 15 [mu]g/dscm. Thus, for the hypothetical wet process
cement kiln the thermal emissions floor level of 1.4 x 10-5
lbs low volatile metals attributable to the hazardous waste per million
Btu heat input of the hazardous waste is estimated to be less than 22
[mu]g/dscm, which is less than the current interim standard of 56
[mu]g/dscm. Given that comparing the proposed floor level to the
interim standard requires numerous assumptions (as just illustrated)
including hazardous waste fuel replacement rates, heat input
requirements per ton of clinker, concentrations of low volatile metals
in the raw material and coal, and system removal efficiency, we have
included a more detailed analysis in the background document.\106\ Our
detailed analysis indicates the proposed floor level is as least as
stringent as the interim standard (so as to avoid any backsliding from
a current level of performance achieved by all cement kilns, and hence,
the level of minimal stringency at which EPA could calculate the MACT
floor). Thus, we conclude that a dual standard--the low volatile metals
standard as both the calculated floor level, expressed as a hazardous
waste thermal emissions level, and the current interim standard--is not
needed for this standard.
---------------------------------------------------------------------------
\106\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 23.
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of low volatile metals: (1) Improved particulate matter
control; (2) control of low volatile metals in the hazardous waste
feed; and (3) control of the low volatile metals in the raw materials.
For reasons discussed below, we are not proposing a beyond-the-floor
standard for low volatile metals.
[[Page 21258]]
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of low volatile metals. Our data show that all
cement kilns are already achieving greater than 99.9% system removal
efficiency for low volatile metals, with most attaining 99.99% removal.
Thus, additional control of particulate matter emissions is likely to
result in only a small increment in reduction of low volatile metals
emissions. We evaluated a beyond-the-floor level of 7.0 x
10-6 lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste,
which represents a 50% reduction in emissions from MACT floor levels.
The national incremental annualized compliance cost for cement kilns to
meet this beyond-the-floor level rather than comply with the floor
controls would be approximately $3.7 million and would provide an
incremental reduction in low volatile metals emissions beyond the MACT
floor controls of 120 pounds per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between further improvements to control particulate matter and
controls likely to be used to meet the floor level. We estimate that
this beyond-the-floor option would increase the amount of solid waste
generated by 72 tons per year and would also require sources to use an
additional 1.2 million kW-hours per year beyond the requirements to
achieve the floor level. The costs associated with these impacts are
accounted for in the national annualized compliance cost estimates.
Therefore, based on these factors and costs of approximately $63
million per additional ton of low volatile metals removed, we are not
proposing a beyond-the-floor standard based on improved particulate
matter control.
Feed Control of Low Volatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 1.1 x 10-5 lbs low
volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
mercury in hazardous waste can be used and still achieve appreciable
emissions reductions. The national incremental annualized compliance
cost for cement kilns to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $1.2 million and
would provide an incremental reduction in low volatile metals emissions
beyond the MACT floor controls of 38 pounds per year. Nonair quality
health and environmental impacts and energy effects were evaluated and
are included in the cost estimates. Therefore, based on these factors
and costs of approximately $64 million per additional ton of low
volatile metals removed, we are not proposing a beyond-the-floor
standard based on feed control of low volatile metals in the hazardous
waste.
Feed Control of Low Volatile Metals in the Raw Materials and
Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile
metal emissions by substituting a raw material containing lower levels
of arsenic, beryllium, and/or chromium for a primary raw material with
higher levels of these metals. We believe that this beyond-the-floor
option would even be less cost-effective than either of the options
discussed above, however. Given that cement kilns are sited near the
primary raw material supply, acquiring and transporting large
quantities of an alternate source of raw materials is likely to be
cost-prohibitive. Therefore, we are not proposing a beyond-the-floor
standard based on limiting low volatile metals in the raw material
feed. We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of low volatile metals would be an
appropriate control option for sources. Given that most cement kilns
burning hazardous waste also burn coal as a fuel, we considered
switching to natural gas as a potential beyond-the-floor option. For
the same reasons discussed for mercury, we judge a beyond-the-floor
standard based on fuel switching as unwarranted.
For the reasons discussed above, we propose to establish the
emission standard for existing cement kilns at 1.4 x 10-5
lbs low volatile metals emissions attributable to the hazardous waste
per million Btu heat input of the hazardous waste.
3. What Is the Rationale for the MACT Floor for New Sources?
Low volatile metals emissions from new cement kilns are currently
limited to 54 [mu]g/dscm by Sec. 63.1204(b)(4). This standard was
promulgated in the Interim Standards Rule (see 67 FR at 6796, February
13, 2002).
The floor level for new sources for low volatile metals would be
1.4 x 10-5 lbs low volatile metals emissions attributable to
the hazardous waste per million Btu heat input of the hazardous waste,
which considers emissions variability. This is an emission level that
the single best performing source identified with the SRE/Feed Approach
could be expected to achieve in 99 of 100 future tests when operating
under conditions identical to the test conditions during which the
emissions data were obtained.
To put the proposed floor level in context for a hypothetical wet
process cement kiln that gets 50% of its required heat input from
hazardous waste, a thermal emissions level of 1.4 x 10-5 lbs
low volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste equates approximately to
a stack gas concentration of 22 [mu]g/dscm, including contributions
from typical raw materials and coal. Thus, for the hypothetical wet
process cement kiln the thermal emissions floor level of 6.2 x
10-\5\ lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste is
estimated to be more stringent than the current interim standard for
new sources of 54 [mu]g/dscm.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same three potential beyond-the-floor techniques
for control of low volatile metals: (1) Improved control of particulate
matter; (2) control of low volatile metals in the hazardous waste feed;
and (3) control of low volatile metals in the raw materials and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of low volatile metals. We evaluated improved
control of particulate matter based on a state-of-the-art baghouse
using a high quality fabric filter bag material as beyond-the-floor
control for further reductions in low volatile metals emissions. We
evaluated a beyond-the-floor level of 6.0 x 10-6 lbs low
volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste. The incremental
annualized compliance cost for a new cement kiln to meet this beyond-
the-floor level, rather than comply with the floor level, would be
approximately $0.38 million and would provide an incremental reduction
in low volatile metals emissions of approximately 33 pounds per year.
Nonair quality health and environmental impacts and energy effects were
evaluated and are included in the cost estimates. For these reasons and
costs of $23.5 million per ton of low volatile metals removed, we are
not proposing a beyond-the-floor standard based on improved particulate
matter control for new cement kilns.
[[Page 21259]]
Feed Control of Low Volatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 1.1 x 10-5 lbs low
volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. We believe that the expense for further
reduction in low volatile metals emissions based on further control of
low volatile metals concentrations in the hazardous waste is not
warranted given the costs, nonair quality health and environmental
impacts, and energy effects.
Feed Control of Low Volatile Metals in the Raw Materials and
Auxiliary Fuels. Cement kilns could achieve a reduction in low volatile
metals emissions by substituting a raw material containing lower levels
of low volatile metals for a primary raw material with a higher level.
For a new source at an existing cement plant, we believe that this
beyond-the-floor option would not be cost-effective due to the costs of
transporting large quantities of an alternate source of raw materials
to the cement plant. Given that the plant site already exists and sited
near the source of raw material, replacing the raw materials at the
plant site with lower low volatile metals-containing materials would be
the source's only option. For a cement kiln constructed at a new
greenfield site, we are not aware of any information and data from a
source that has undertaken or is currently located at a site whose raw
materials are inherently lower in low volatile metals that would
consistently achieve reduced low volatile metals emissions. Further, we
are uncertain as to what beyond-the-floor standard would be achievable
using a lower, if it exists, low volatile metals-containing raw
material. Although we are doubtful that selecting a new plant site
based on the content of metals in the raw material is a realistic
beyond-the-floor option considering the numerous additional factors
that go into such a decision, we solicit comment on whether and what
level of a beyond-the-floor standard based on controlling the level of
low volatile metals in the raw materials is appropriate.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of low volatile metals would be an
appropriate control option for sources. Given that most cement kilns
burning hazardous waste also burn coal as a fuel, we considered
switching to natural gas as a potential beyond-the-floor option. For
the same reasons discussed for mercury, we judge a beyond-the-floor
standard based on fuel switching as unwarranted.
Therefore, we are proposing a low volatile metals standard of 1.4 x
10-5 lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste.
F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine
Gas?
We are proposing to establish standards for existing and new cement
kilns that limit total chlorine emissions (hydrogen chloride and
chlorine gas, combined, reported as a chloride equivalent) to 110 and
83 ppmv, respectively. However, we are also proposing to establish
alternative risk-based standards, pursuant to CAA section 112(d)(4),
which could be elected by the source in lieu of the MACT emission
standards for total chlorine. The emission limits would be based on
national exposure standards that ensure protection of public health
with an ample margin of safety. See Part Two, Section XIII for
additional details.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Total chlorine emissions from existing cement kilns are limited to
130 ppmv by Sec. 63.1204(a)(6). This standard was promulgated in the
Interim Standards Rule (See 67 FR at 6796). None of the cement kilns
burning hazardous waste use a dedicated control device, such as a wet
scrubber, to remove total chlorine from the gas stream. However, the
natural alkalinity in some of the raw materials is highly effective at
removing chlorine from the gas stream. Our data base shows that the
majority of the system removal efficiency (SRE) data of total
chlorine--over 80%--indicate a SRE greater than 95%. This scrubbing
effect, though quite effective, varies across different sources and
also at individual sources over time due to differences in raw
materials, operating conditions, cement kiln dust recycle rates, and
production requirements. Likewise, our data show that total chlorine
emissions from a given source can vary over a considerable range. Based
on these data, we conclude that the best (highest) SRE achieved at a
given source is not duplicable or replicable.
The majority of the chlorine fed to the cement kiln during a
compliance test comes from the hazardous waste.\107\ In all but a few
cases the hazardous waste contribution to the total amount of chlorine
fed to the kiln represented at least 75% of the total chlorine loading
to the kiln. As we identified in the September 1999 final rule, the
proposed MACT floor control for total chlorine is based on controlling
the concentration of chlorine in the hazardous waste. The chlorine
concentration in the hazardous waste will affect emissions of total
chlorine at a given SRE because emissions increase as the chlorine
loading increases.
---------------------------------------------------------------------------
\107\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards'',
March 2004, Chapter 2.
---------------------------------------------------------------------------
We have compliance test emissions data for all cement kiln sources.
For most sources, we have compliance test emissions data from more than
one compliance test campaign. Total chlorine emissions range from less
than 1 ppmv to 192 ppmv.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using a
variant of the SRE/Feed Approach because of concerns about a cement
kiln's ability to replicate a given SRE. To identify the floor level we
first evaluated the chlorine feed level in the hazardous waste for all
sources. The best performing sources had the lowest maximum theoretical
emissions concentration or MTEC, considering variability. We then
applied a SRE of 90% to the best performing sources' total MTEC (i.e.,
includes chlorine contributions to emissions from all feedstreams such
as raw material and fossil fuels) to identify the floor level. Given
our concerns about the reproducibility of SREs of total chlorine, we
selected a SRE of 90% because our data base shows that all sources have
demonstrated this SRE at least once (and often several times) during a
compliance test. The calculated floor is 110 ppmv, which considers
emissions variability. This is an emission level that the best
performing feed control sources could be expected to achieve in 99 of
100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 93%
of sources and would reduce total chlorine emissions by 64 tons per
year.
We also invite comment on an alternative approach to establish a
floor level expressed as a hazardous waste thermal feed
concentration.\108\ A hazardous waste thermal feed concentration is
expressed as mass of chlorine in the hazardous waste per
[[Page 21260]]
million Btu heat input contributed by the hazardous waste. The floor
would be based on the best five performing sources with the lowest
thermal feed concentration of chlorine in the hazardous waste
considering each source's most recent compliance test data. One
advantage of this approach is that the uncertainty surrounding the
capture (SRE) of chlorine in a kiln is removed. The calculated floor
level would be 2.4 lbs chlorine in the hazardous waste per million Btu
in the hazardous waste, which considers variability. For a hypothetical
wet process cement kiln that gets 50% of its required heat input from
hazardous waste, a hazardous waste with a chlorine concentration of 2.4
lbs chlorine per million Btu and achieving 90% SRE equates
approximately to a stack gas concentration of 75 ppmv. This estimated
stack gas concentration does not include contributions to emission from
other chlorine-containing materials such as raw materials and fossil
fuels. The additional contribution to stack emissions of total chlorine
in an average raw material and coal is estimated to range from less
than 1 to 35 ppmv. Thus, for the hypothetical wet process cement kiln
this floor level is estimated to be less than 110 ppmv, which is less
than the current interim standard of 130 ppmv.
---------------------------------------------------------------------------
\108\ We are also requesting comment on whether the hazardous
waste feed concentration floor level should be the standard itself
(i.e., no stack emission concentration standard) or as an
alternative to the stack emission standard (e.g., sources have the
opinion to comply with either the calculated stack emissions
concentration or the hazardous waste feed concentration limit).
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of total chlorine: (1) Use of wet scrubbers; (2) control of
chlorine in the hazardous waste feed; and (3) control of the chlorine
in the raw materials. For reasons discussed below, we are not proposing
a beyond-the-floor standard for total chlorine.
Use of Wet Scrubbers. We evaluated the use of wet scrubbers as
beyond-the-floor control for further reduction of mercury emissions.
Wet scrubbers are not currently being used at any hazardous waste
burning cement kilns to capture hydrogen chloride. We evaluated a
beyond-the-floor level of 55 ppmv. The national incremental annualized
compliance cost for cement kilns to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $3.4
million and would provide an incremental reduction in total chlorine
emissions beyond the MACT floor controls of 370 tons per year. Nonair
quality health and environmental impacts and energy effects were
evaluated to estimate the impacts between wet scrubbing and controls
likely to be used to meet the floor level. We estimate that this
beyond-the-floor option would increase the amount of water usage and
waste water generated by 1.5 billion gallon per year. The option would
also require sources to use an additional 12 million kW-hours per year
beyond the requirements to achieve the floor level. The costs
associated with these impacts are accounted for in the national
annualized compliance cost estimates. Therefore, based on these factors
and costs of approximately $9,300 per additional ton of total chlorine
removed, we are not proposing a beyond-the-floor standard based on wet
scrubbing.
Feed Control of Chlorine in the Hazardous Waste. We also evaluated
a beyond-the-floor level of 88 ppmv, which represents a 20% reduction
from the floor level. We chose a 20% reduction as a level that
represents the practicable extent that additional feedrate control of
chlorine in the hazardous waste can be used and still achieve modest
emissions reductions. The national incremental annualized compliance
cost for cement kilns to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $1.1 million and
would provide an incremental reduction in total chlorine emissions
beyond the MACT floor controls of 100 tons per year. Nonair quality
health and environmental impacts and energy effects were also evaluated
and are included in the compliance cost estimates. Therefore, based on
these factors and costs of approximately $11,000 per additional ton of
total chlorine, we are not proposing a beyond-the-floor standard based
on feed control of chlorine in the hazardous waste.
Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels.
Cement kilns could achieve a reduction in total chlorine emissions by
substituting a raw material containing lower levels of chlorine for a
primary raw material with higher levels of chlorine. We believe that
this beyond-the-floor option would even be less cost-effective than
either of the options discussed above because most chlorine feed to the
kiln is in the hazardous waste. In addition, given that cement kilns
are sited near the primary raw material supply, acquiring and
transporting large quantities of an alternate source of raw materials
is likely to be cost-prohibitive. Therefore, we are not proposing a
beyond-the-floor standard based on limiting chlorine in the raw
material feed. We also considered whether fuel switching to an
auxiliary fuel containing a lower concentration of chlorine would be an
appropriate control option for kilns. Given that most cement kilns
burning hazardous waste also burn coal as a fuel, we considered
switching to natural gas as a potential beyond-the-floor option. For
the same reasons discussed for mercury, we judge a beyond-the-floor
standard based on fuel switching as unwarranted.
For the reasons discussed above, we propose not to adopt a beyond-
the-floor standard for total chlorine and propose to establish the
emission standard for existing cement kilns at 110 ppmv.
3. What Is the Rationale for the MACT Floor for New Sources?
Total chlorine emissions from new cement kilns are currently
limited to 86 ppmv by Sec. 63.1204(b)(6). This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6796). The MACT
floor for new sources for total chlorine would be 78 ppmv, which
considers emissions variability. This is an emission level that the
single best performing source identified with the SRE/Feed Approach
could be expected to achieve in 99 of 100 future tests when operating
under conditions identical to the test conditions during which the
emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified similar potential beyond-the-floor techniques for
control of total chlorine for new sources: (1) Use of wet scrubbing;
(2) control of chlorine in the hazardous waste feed; and (3) control of
chlorine in the raw materials and fuels.
Use of Wet Scrubbers. We considered wet scrubbing as beyond-the-
floor control for further reductions in total chlorine emissions and
evaluated a beyond-the-floor level of 39 ppmv. The incremental
annualized compliance cost for a new cement kiln to meet this beyond-
the-floor level, rather than comply with the floor level, would be
approximately $1.2 million and would provide an incremental reduction
in total chlorine emissions of approximately 22 tons per year. Nonair
quality health and environmental impacts and energy effects were
evaluated and are included in the cost estimates. For these reasons and
costs of $24,000 per ton of total chlorine removed, we are not
proposing a beyond-the-floor standard based on wet scrubbing for new
cement kilns.
Feed Control of Low Volatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 62 ppmv, which represents a 20%
reduction from the floor level. We believe that the expense for further
reduction in total chlorine emissions
[[Page 21261]]
based on further control of chlorine concentrations in the hazardous
waste is not warranted given the costs, nonair quality health and
environmental impacts, and energy effects.
Feed Control of Chlorine in the Raw Materials and Auxiliary Fuels.
Cement kilns could achieve a reduction in total chlorine emissions by
substituting a raw material containing lower levels of chlorine for a
primary raw material with a higher level. For a new source at an
existing cement plant, we believe that this beyond-the-floor option
would not be cost-effective due to the costs of transporting large
quantities of an alternate source of raw materials to the cement plant.
Given that the plant site already exists and sited near the source of
raw material, replacing the raw materials at the plant site with lower
chlorine-containing materials would be the source's only option. For a
cement kiln constructed at a new greenfield site, we are not aware of
any information and data from a source that has undertaken or is
currently located at a site whose raw materials are inherently lower in
chlorine that would consistently achieve reduced total chlorine
emissions. Further, we are uncertain as to what beyond-the-floor
standard would be achievable using a lower, if it exists, chlorine-
containing raw material. Although we are doubtful that selecting a new
plant site based on the content of chlorine in the raw material is a
realistic beyond-the-floor option considering the numerous additional
factors that go into such a decision, we solicit comment on whether and
what level of a beyond-the-floor standard based on controlling the
level of chlorine in the raw materials is appropriate.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of chlorine would be an appropriate
control option for sources. Given that most cement kilns burning
hazardous waste also burn coal as a fuel, we considered switching to
natural gas as a potential beyond-the-floor option. For the same
reasons discussed for mercury, we judge a beyond-the-floor standard
based on fuel switching as unwarranted.
Therefore, we are proposing a total chlorine standard of 78 ppmv
for new cement kilns.
G. What Are the Standards for Hydrocarbons and Carbon Monoxide?
Hydrocarbon and carbon monoxide standards are surrogates to control
emissions of organic hazardous air pollutants for existing and new
cement kilns. For cement kilns without bypass or midkiln sampling
systems, the standard for existing sources limit hydrocarbon or carbon
monoxide concentrations to 20 ppmv or 100 ppmv, respectively. The
standards for new sources limit (1) hydrocarbons to 20 ppmv; or (2)
carbon monoxide to 100 ppmv. New, greenfield kilns\109\, that elect to
comply with the 100 ppmv carbon monoxide standard, however, must also
comply with a 50 ppmv hydrocarbon standard. New and existing sources
that elect to comply with the 100 ppmv carbon monoxide standard,
including new greenfield kilns that elect to comply with the carbon
monoxide standard and 50 ppmv hydrocarbon standard, must also
demonstrate compliance with the 20 ppmv hydrocarbon standard during the
comprehensive performance test. However, continuous hydrocarbon
monitoring following the performance test is not required.
---------------------------------------------------------------------------
\109\ A greenfield cement kiln is a kiln that commenced
construction or reconstruction after April 19, 1996 at a site where
no cement kiln previously existed, irrespective of the class of kiln
(i.e., nonhazardous waste or hazardous waste burning). A newly
constructed or reconstructed cement kiln at an existing site is not
classified as a greenfield cement kiln, and is subject to the same
carbon monoxide and hydrocarbon standards as an existing cement
kiln.
---------------------------------------------------------------------------
For cement kilns with bypass or midkiln sampling systems, existing
cement kilns are required to comply with either a carbon monoxide
standard of 100 ppmv or a hydrocarbon standard of 10 ppmv. Both
standards apply to combustion gas sampled in the bypass or a midkiln
sampling port that samples representative kiln gas. See Sec. Sec.
63.1204(a)(5) and (b)(5). The rationale for these decisions are
discussed in the September 1999 final rule (64 FR at 52885). We view
the standards for hydrocarbons and carbon monoxide as unaffected by the
Court's vacature of the challenged regulations in its decision of July
24, 2001. We therefore are not proposing these standards for cement
kilns, but rather are mentioning them here for the reader's
convenience.
H. What Are the Standards for Destruction and Removal Efficiency?
The destruction and removal efficiency (DRE) standard is a
surrogate to control emissions of organic hazardous air pollutants
other than dioxin/furans. The standard for existing and new lightweight
aggregate kilns requires 99.99% DRE for each principal organic
hazardous constituent, except that 99.9999% DRE is required if
specified dioxin-listed hazardous wastes are burned. See Sec. Sec.
63.1204(c). The rationale for these decisions are discussed in the
September 1999 final rule (64 FR at 52890). We view the standards for
DRE as unaffected by the Court's vacature of the challenged regulations
in its decision of July 24, 2001. We therefore are not proposing these
standards for cement kilns, but rather are mentioning them here for the
reader's convenience.
IX. How Did EPA Determine the Proposed Emission Standards for Hazardous
Waste Burning Lightweight Aggregate Kilns?
In this section, the basis for the proposed emission standards is
discussed. See proposed Sec. 63.1221. The proposed emission limits
apply to the stack gases from lightweight aggregate kilns that burn
hazardous waste and are summarized in the table below:
Proposed Standards for Existing and New Lightweight Aggregate Kilns
------------------------------------------------------------------------
Emission standard \1\
Hazardous air pollutant or -------------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan............ 0.40 ng TEQ/dscm.... 0.40 ng TEQ/dscm.
Mercury \2\................. 67 [mu]g/dscm....... 67 [mu]g/dscm.
Particulate Matter.......... 57 mg/dscm (0.025 gr/ 23 mg/dscm (0.0099
dscf). gr/dscf).
Semivolatile metals \3\..... 3.1 x 10-4 lb/MMBtu 2.4 x 10-5 lb/MMBtu
and 250 [mu]g/dscm. and 43 [mu]g/dscm.
Low volatile metals \3\..... 9.5 x 10-5 lb/MMBtu 3.2 x 10-5 lb/MMBtu
and 110 [mu]g/dscm. and 110 [mu]g/dscm.
Hydrogen chloride and 600 ppmv............ 600 ppmv.
chlorine gas \4\.
Hydrocarbons 5, 6........... 20 ppmv (or 100 ppmv 20 ppmv (or 100 ppmv
carbon monoxide). carbon monoxide).
[[Page 21262]]
Destruction and removal For existing and new sources, 99.99% for
efficiency. each principal organic hazardous
constituent (POHC). For sources burning
hazardous wastes F020, F021, F022, F023,
F026, or F027, however, 99.9999% for each
POHC.
------------------------------------------------------------------------
\1\ All emission standards are corrected to 7% oxygen, dry basis.
\2\ Mercury standard is an annual limit.
\3\ Standards are expressed as mass of pollutant emissions contributed
by hazardous waste per million British thermal unit contributed by the
hazardous waste.
\4\ Combined standard, reported as a chloride (Cl(-)) equivalent.
\5\ Sources that elect to comply with the carbon monoxide standard must
demonstrate compliance with the hydrocarbon standard during the
comprehensive performance test.
\6\ Hourly rolling average. Hydrocarbons reported as propane.
A. What Are the Proposed Standards for Dioxin and Furan?
We are proposing to establish standards for existing and new
lightweight aggregate kilns that limit emissions of dioxin and furans
to 0.40 ng TEQ/dscm.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Dioxin and furan emissions for existing lightweight aggregate kilns
are currently limited by Sec. 63.1205(a)(1) to 0.20 ng TEQ/dscm or
rapid quench of the flue gas at the exit of the kiln to less than
400[deg]F. This standard was promulgated in the Interim Standards Rule
(See 67 FR at 6797).
Since promulgation of the September 1999 final rule, we have
obtained additional dioxin/furan emissions data. We now have compliance
test emissions data for all lightweight aggregate kilns that burn
hazardous waste. The compliance test dioxin/furan emissions in our
database range from approximately 0.9 to 58 ng TEQ/dscm.
Quenching kiln gas temperatures at the exit of the kiln so that gas
temperatures at the inlet to the particulate matter control device are
below the temperature range of optimum dioxin/furan formation (400-
750[deg]F) may be problematic for some of these sources. Some of these
sources have extensive (long) duct-work between the kiln exit and the
inlet to the control device. For these sources, quenching the gases at
the kiln exit to a low enough temperature to limit dioxin/furan
formation may conflict with the source's ability to avoid acid gas dew
point related problems in the long duct-work and control device. As a
result, some sources quench the kiln exit gases to a temperature that
is in the optimum temperature range for surface-catalyzed dioxin/furan
formation. Available compliance test emissions data indicate that inlet
temperatures to the control device range from 435-450[deg]F. This means
that temperatures in the duct-work are higher and well within the range
of optimum dioxin/furan formation.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
Emissions Approach described in Part Two, Section VI above. The
calculated floor is 14 ng TEQ/dscm, which considers emissions
variability. However, the current interim emission standard--0.20 ng
TEQ/dscm or rapid quench of the flue gas at the exit of the kiln to
less than 400[deg]F--is a regulatory limit that is relevant in
identifying the floor level because it fixes a level of performance for
the source category. We estimate that sources achieving the ``rapid
quench of the flue gas at the exit of the kiln to less than 400[deg]F''
part of the current standard can emit up to 6.1 ng TEQ/dscm. Given that
all sources are achieving the interim standard and that the interim
standard is judged as more stringent than the calculated MACT floor,
the dioxin/furan floor level can be no less stringent than the current
regulatory limit.\110\ We are, therefore, proposing the dioxin/furan
floor level as the current emission standard of 0.20 ng TEQ/dscm or
rapid quench of the flue gas at the exit of the kiln to less than
400[deg]F. This emission level is being achieved by all sources because
it is the interim standard. In addition, there are no emissions
reductions for existing lightweight aggregate kilns to comply with the
floor level.
---------------------------------------------------------------------------
\110\ Even though all sources have recently demonstrated
compliance with the interim standards, the dioxin/furan data in our
data base preceded the compliance demonstration. This explains why
we have emissions data that are higher than the interim standard.
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated activated carbon injection as beyond-the-floor control
for further reduction of dioxin/furan emissions. Activated carbon has
been demonstrated for controlling dioxin/furans in various combustion
applications; however, no lightweight aggregate kiln that burns
hazardous waste uses activated carbon injection. We evaluated a beyond-
the-floor level of 0.40 ng TEQ/dscm, which represents a level that is
considered routinely achievable using activated carbon injection. In
addition, we assumed for costing purposes that lightweight aggregate
kilns needing activated carbon injection to achieve the beyond-the-
floor level would install the activated carbon injection system after
the existing particulate matter control device and add a new, smaller
baghouse to remove the injected carbon with the adsorbed dioxin/furans.
We chose this costing approach to address potential concerns that
injected carbon may interfere with lightweight aggregate dust use
practices.
The national incremental annualized compliance cost for lightweight
aggregate kilns to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $1.8 million and would
provide an incremental reduction in dioxin/furan emissions beyond the
MACT floor controls of 1.9 grams TEQ per year. Nonair quality health
and environmental impacts and energy effects were evaluated to estimate
the nonair quality health and environmental impacts between activated
carbon injection and controls likely to be used to meet the floor
level. We estimate that this beyond-the-floor option would increase the
amount of solid waste generated by 550 tons per year and would require
sources to use an additional 1 million kW-hours per year beyond the
requirements to achieve the floor level. The costs associated with
these impacts are accounted for in the national compliance cost
estimates.
Therefore, based on these factors and costs of approximately $0.95
million per additional gram of dioxin/furan TEQ
[[Page 21263]]
removed, we are proposing a beyond-the-floor standard of 0.40 ng TEQ/
dscm for existing lightweight aggregate kilns. We judge that the cost
to achieve this beyond-the-floor level is warranted given our special
concern about dioxin/furan. Dioxin/furan are some of the most toxic
compounds known due to their bioaccumulation potential and wide range
of health effects, including carcinogenesis, at exceedingly low doses.
Exposure via indirect pathways is a chief reason that Congress singled
our dioxin/furan for priority MACT control in CAA section 112(c)(6).
See S. Rep. No. 128, 101st Cong. 1st Sess. at 154-155. In addition, we
note that a beyond-the-floor standard of 0.40 ng TEQ/dscm is consistent
with historically controlled levels under MACT for hazardous waste
incinerators and cement kilns, and Portland cement plants. See
Sec. Sec. 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). Also, EPA
has determined previously in the 1999 Hazardous Waste Combustor MACT
final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less
are necessary for the MACT standards to be considered generally
protective of human health under RCRA (using the 1985 cancer slope
factor), thereby eliminating the need for separate RCRA standards under
the authority of RCRA section 3005(c)(3) and 40 CFR 270.10(k). Finally,
we note that this decision is not inconsistent with EPA's decision not
to promulgate beyond-the-floor standards for dioxin/furan for hazardous
waste burning lightweight aggregate kilns, cement kilns, and
incinerators at cost-effectiveness values in the range of $530,000 to
$827,000 per additional gram of dioxin/furan TEQ removed. See 64 FR at
52892, 52876, and 52961. In those cases, EPA determined that
controlling dioxin/furan emissions from a level of 0.40 ng TEQ/dscm to
a beyond-the-floor level of 0.20 ng TEQ/dscm was not warranted because
dioxin/furan levels below 0.40 ng TEQ/dscm are generally considered to
be below the level of health risk concern.
We specifically request comment on whether this beyond-the-floor
standard is warranted.
3. What Is the Rationale for the MACT Floor for New Sources?
Dioxin and furan emissions for new lightweight aggregate kilns are
currently limited by Sec. 63.1205(b)(1) to 0.20 ng TEQ/dscm or rapid
quench of the flue gas at the exit of the kiln to less than 400[deg]F.
This standard was promulgated in the Interim Standards Rule (See 67 FR
at 6797).
The calculated MACT floor for new sources would be 1.3 ng TEQ/dscm,
which considers emissions variability, or rapid quench of the flue gas
at the exit of the kiln to less than 400[deg]F. This is an emission
level that the single best performing source identified by the
Emissions Approach. However, we are concerned that the calculated floor
level of 1.3 ng TEQ/dscm is not duplicable by all sources using
temperature control because we estimate that sources rapidly quenching
the flue gas at the exit of the kiln to less than 400[deg]F can emit up
to 6.1 ng TEQ/dscm. Therefore, we are proposing the floor as the
current emission standard of 0.20 ng TEQ/dscm or rapid quench of the
flue gas at the exit of the kiln to less than 400[deg]F.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated activated carbon injection as beyond-the-floor control
for further reduction of dioxin/furan emissions, and considered a
beyond-the-floor level of 0.40 ng TEQ/dscm, which represents a level
that is considered routinely achievable with activated carbon
injection. In addition, we assumed for costing purposes that a new
lightweight aggregate kiln will install the activated carbon injection
system after the existing particulate matter control device and add a
new, smaller baghouse to remove the injected carbon with the adsorbed
dioxin/furan. The incremental annualized compliance cost for a new
source to meet this beyond-the-floor level, rather than comply with the
floor level, would be approximately $0.26 million and would provide an
incremental reduction in dioxin/furan emissions of 0.37 grams per year.
Nonair quality health, environmental impacts, and energy effects are
accounted for in the cost estimates. Therefore, based on these factors
and cost of $0.71 million per gram TEQ removed, we are proposing a
beyond-the-floor standard based on activated carbon injection. We
believe that the cost to achieve this beyond-the-floor level is
warranted given our special concern about dioxin/furan. Dioxin/furan
are some of the most toxic compounds known due to their bioaccumulation
potential and wide range of health effects, including carcinogenesis,
at exceedingly low doses. In addition, as discussed above, we note that
the beyond-the-floor emission level of 0.40 ng TEQ/dscm is consistent
with historically controlled levels under MACT for hazardous waste
incinerators and cement kilns, and Portland cement plants. See
Sec. Sec. 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). EPA has
determined previously in the 1999 Hazardous Waste Combustor MACT final
rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less are
necessary for the MACT standards to be considered generally protective
of human health under RCRA, thereby eliminating the need for separate
RCRA standards.
We specifically request comment on whether this beyond-the-floor
standard is warranted.
B. What Are the Proposed Standards for Mercury?
We are proposing to establish standards for existing and new
lightweight aggregate kilns that limit emissions of mercury to 67
[mu]g/dscm.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Mercury emissions for existing lightweight aggregate kilns are
currently limited to 120 [mu]g/dscm by Sec. 63.1205(a)(2). Existing
lightweight aggregate kilns have the option to comply with an
alternative mercury standard that limits the hazardous waste maximum
theoretical emissions concentration (MTEC) of mercury to 120 [mu]g/
dscm.\111\ This standard was promulgated in the Interim Standards Rule
(See 67 FR at 6797). One lightweight aggregate facility with two kilns
uses a venturi scrubber to remove mercury from the flue gas stream and
the remaining sources limit the feed concentration of mercury in the
hazardous waste to control emissions.
---------------------------------------------------------------------------
\111\ MTEC is a term to compare metals and chlorine feedrates
across sources of different sizes. MTEC is defined as the metals or
chlorine feedrate divided by the gas flow rate and is expressed in
units of [mu]g/dscm.
---------------------------------------------------------------------------
We have compliance test emissions data for only one source;
however, we have normal emissions data for all sources. For most
sources, we have normal emissions data from more than one test
campaign. We used these emissions data to represent the average
emissions from a source even though we do not know whether the
emissions represent the high end, low end, or close to the average
emissions. The normal mercury stack emissions range from less than 1 to
47 [mu]g/dscm, while the highest compliance test emissions data is
1,050 [mu]g/dscm. These emissions are expressed as mass of mercury
(from all feedstocks) per unit volume of stack gas.
To identify the MACT floor, we evaluated all normal emissions data
using the SRE/Feed Approach. We considered normal stack emissions data
from all test campaigns.\112\ For example,
[[Page 21264]]
one source in our data base has normal emissions data for three
different testing campaigns: 1992, 1995, and 1999. Under this approach
we considered the emissions data from the three separate years or
campaigns. As explained earlier, we believe this approach better
captures the range of average emissions for a source than only
considering the most recent normal emissions. In addition, for sources
without control equipment to capture mercury, we assumed the sources
achieved a SRE of zero. The effect of this assumption is that the
sources (without control equipment for mercury) with the lower mercury
concentrations in the hazardous waste were identified as the better
performing sources.
---------------------------------------------------------------------------
\112\ Given that the majority of feedrate and emissions data for
mercury is normal, we do not believe it is appropriate to establish
a hazardous waste thermal emissions-based standard. We prefer to
establish emission standards under the hazardous waste thermal
emissions format using compliance test data because the metals
feedrate information from compliance tests that we use to apportion
emissions to calculate emissions attributable to hazardous waste are
more reliable than feedrate data measured during testing under
normal, typical operations.
---------------------------------------------------------------------------
The calculated floor is 67 [mu]g/dscm, which considers emissions
variability, based on a hazardous waste maximum theoretical emissions
concentration (MTEC) of 42 [mu]g/dscm. This is an emission level that
the average of the best performing sources could be expected to achieve
in 99 of 100 future tests when operating under operating conditions
identical to the compliance test conditions during which the emissions
data were obtained. We estimate that this emission level is being
achieved by 57% of sources and would reduce mercury emissions by 8
pounds per year. If we were to adopt such a floor level, we are
proposing that sources comply with the limit on an annual basis because
it is based on normal emissions data. Under this approach, compliance
would not be based on the use of a total mercury continuous emissions
monitoring system because these monitors have not been adequately
demonstrated as a reliable compliance assurance tool at all types of
incinerator sources. Instead, a source would maintain compliance with
the mercury standard by establishing and complying with short-term
limits on operating parameters for pollution control equipment and
annual limits on maximum total mercury feedrate in all feedstreams.
In the September 1999 final rule, we acknowledged that a
lightweight aggregate kiln using properly designed and operated MACT
control technologies, including controlling the levels of metals in the
hazardous waste, may not be capable of achieving a given emission
standard because of process raw material contributions that might cause
an exceedance of the emission standard. To address this concern, we
promulgated a provision that allows sources to petition for alternative
standards provided they submit site-specific information that shows raw
material hazardous air pollutant contributions to the emissions prevent
the source from complying with the emission standard even though the
kiln is using MACT control. See Sec. 63.1206(b)(9).
Today's proposed floor of 67 [mu]g/dscm, which was based on a
hazardous waste MTEC of 42 [mu]g/dscm, may likewise necessitate such an
alternative because contributions of mercury in the raw materials and
fossil fuels at some sources may cause an exceedance of the emission
standard. The Agency intends to retain a source's ability to comply
with an alternative standard, and we request comment on two approaches
to accomplish this. The first approach would be to structure the
alternative standard similar to the petitioning process used under
Sec. 63.1206(b)(9). In the case of mercury for an existing lightweight
aggregate kiln, MACT would be defined as a hazardous waste feedrate
corresponding to an MTEC of 42 [mu]g/dscm. If we were to adopt this
approach, we would require sources, upon approval of the petition by
the Administrator, to comply with this hazardous waste MTEC on an
annual basis because it is based on normal emissions data. Under the
second approach, we would structure the alternative standard similar to
the framework used for the alternative interim standards for mercury
under Sec. 63.1206(b)(15). The operating requirement would be an
annual MTEC not to exceed 42 [mu]g/dscm. We also request comment on
whether there are other approaches that would more appropriately
provide relief to sources that cannot achieve a total stack gas
concentration standard because of emissions attributable to raw
material and nonhazardous waste fuels.
In comments submitted to EPA in 1997, Solite Corporation (Solite),
owner and operator of five \113\ of the seven lightweight aggregate
kilns, stated that the normal emissions data in our data base are
unrepresentative of average emissions of mercury because the normal
range of mercury concentrations in the hazardous waste burned during
the compliance and trial burn tests was not captured during the tests.
In their 1997 comments, Solite provided information on actual mercury
concentrations in the hazardous waste burn tanks over a year and a
quarter period. The information showed that 87% of the burn tanks
contained mercury at concentrations below the facility's detection
limit of 2 ppm. Additional analyses of a limited number of these
samples conducted at an off-site lab showed that the majority of
samples were actually less than 0.2 ppm.\114\
---------------------------------------------------------------------------
\113\ Solite Corporation has four kilns at its Cascade facility
and three kilns at its Arvonia facility. However, only three kilns
and two kilns, respectively, can be fired with hazardous waste at
any one time. For purposes of today's proposal, Solite Corporation
is assumed to operate a total of five kilns.
\114\ A hazardous waste with a mercury concentration of 2 ppm
equates approximately to a mercury emissions level of 200-250 [mu]g/
dscm, and a source firing a hazardous waste with a mercury
concentration of 0.2 ppm approximately equates to 20-25 [mu]g/dscm.
The existing standard of 120 [mu]g/dscm allows a source to burn a
hazardous waste with a mercury concentration of approximately 1 ppm.
---------------------------------------------------------------------------
We examined the test reports of the five best performing sources
that are the basis of today's proposed floor level to determine the
concentration level of mercury in the hazardous wastes. The hazardous
waste burned by the best performing sources during the tests that
generated the normal emissions data had mercury concentrations that
ranged from 0.02 to 0.2 ppm.\115\ Even though the concentrations of
mercury in the hazardous waste seem low, we cannot judge how these snap
shot concentrations compare to long-term normal concentrations because
the majority of the burn tank concentration data submitted by Solite
are nondetect measurements at a higher detection limit.
---------------------------------------------------------------------------
\115\ These mercury concentrations were analyzed by an off-site
lab that had equipment capable of detecting mercury at lower
concentrations. Sixteen of the 27 measurements of the best
performers were reported as non-detects.
---------------------------------------------------------------------------
Solite informed us in July 2003 that they are in the process of
upgrading the analysis equipment at their on-site laboratory. Once
completed, Solite expects to be capable of detecting mercury in the
hazardous waste at concentrations of 0.2 ppm. Solite also indicated
that they intend to assemble and submit to EPA several months of burn
tank concentration data analyzed with the new equipment. We will add
these data to the docket of today's proposal once available. As we
discussed for cement kilns for mercury, we are requesting comment on
approaches to establish a hazardous waste feed concentration standard
based on long-term feed concentrations of mercury in the hazardous
waste. Likewise, we invite comments on establishing a mercury feed
[[Page 21265]]
concentration standard for lightweight aggregate kilns.
We also invite comment on whether we should judge an annual limit
of 67 [mu]g/dscm as less stringent than either the current emission
standard of 120 [mu]g/dscm or the hazardous waste MTEC of mercury of
120 [mu]g/dscm for lightweight aggregate kilns (so as to avoid any
backsliding from a current level of performance achieved by all
sources, and hence, the level of minimal stringency at which EPA could
calculate the MACT floor). In order to comply with the current emission
standard, generally a source must conduct manual stack sampling to
demonstrate compliance with the mercury emission standard and then
establish a maximum mercury feedrate limit based on operations during
the performance test. Following the performance test, the source
complies with a limit on the maximum total mercury feedrate in all
feedstreams on a 12-hour rolling average (not an annual average).
Alternatively, a source can elect to comply with a hazardous waste MTEC
of mercury of 120 [mu]g/dscm that would require the source to limit the
mercury feedrate in the hazardous waste on a 12-hour rolling average.
The floor level of 67 [mu]g/dscm proposed today would allow a source to
feed more variable mercury-containing feedstreams (e.g., a hazardous
waste with a mercury MTEC greater than 120 [mu]g/dscm) than the current
12-hour rolling average because today's proposed floor level is an
annual limit. For example, the concentration of mercury in the
hazardous waste exceeded a hazardous waste MTEC of 120 [mu]g/dscm in a
minimum of 13% of the burn tanks based on the data submitted by Solite
in their 1997 comments (discussed above). As mentioned above, Solite
intends to submit several months of burn tank concentration data using
upgraded analysis equipment at their on-site laboratory that we will
consider when comparing the relative stringency of an annual limit of
67 [mu]g/dscm and a short-term limit of 120 [mu]g/dscm.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of mercury: (1) Activated carbon injection; (2) control of
mercury in the hazardous waste feed; and (3) control of mercury in the
raw materials and auxiliary fuels. For reasons discussed below, we are
not proposing a beyond-the-floor standard for mercury.
Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. Activated carbon has been demonstrated for controlling
mercury in several combustion applications; however, currently no
lightweight aggregate kiln that burns hazardous waste uses activated
carbon injection. Given this lack of experience using activated carbon
injection, we made a conservative assumption that the use of activated
carbon injection will provide 70% mercury control and evaluated a
beyond-the-floor level of 20 [mu]g/dscm. In addition, for costing
purposes we assumed that sources needing activated carbon injection to
achieve the beyond-the-floor level would install the activated carbon
injection system after the existing baghouse and add a new, smaller
baghouse to remove the injected carbon with the adsorbed mercury. We
chose this costing approach to address potential concerns that injected
carbon may interfere with lightweight aggregate kiln dust use
practices.
The national incremental annualized compliance cost for lightweight
aggregate kilns to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $1.1 million and would
provide an incremental reduction in mercury emissions beyond the MACT
floor controls of 11 pounds per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between activated carbon injection and controls likely to be
used to meet the floor level. We estimate that this beyond-the-floor
option would increase the amount of solid waste generated by 270 tons
per year and would require sources to use an additional 1.2 million kW-
hours per year beyond the requirements to achieve the floor level. The
costs associated with these impacts are accounted for in the national
annualized compliance cost estimates. Therefore, based on these factors
and costs of approximately $209 million per additional ton of mercury
removed, we are not proposing a beyond-the-floor standard based on
activated carbon injection.
Feed Control of Mercury in the Hazardous Waste. We also evaluated a
beyond-the-floor level of 54 [mu]g/dscm, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
mercury in hazardous waste (beyond feedrate control that may be
necessary to achieve the floor level) can be used and still achieve
modest emissions reductions.\116\ The national incremental annualized
compliance cost for lightweight aggregate kilns to meet this beyond-
the-floor level rather than comply with the floor controls would be
approximately $0.3 million and would provide an incremental reduction
in mercury emissions beyond the MACT floor controls of 3 pounds per
year. Nonair quality health and environmental impacts and energy
effects were also evaluated. Therefore, based on these factors and
costs of approximately $229 million per additional ton of mercury
removed, we are not proposing a beyond-the-floor standard based on feed
control of mercury in the hazardous waste.
---------------------------------------------------------------------------
\116\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume V: Emission Estimates and Engineering
Costs'', March 2004, Chapter 4.
---------------------------------------------------------------------------
Feed Control of Mercury in the Raw Materials and Auxiliary Fuels.
Lightweight aggregate kilns could achieve a reduction in mercury
emissions by substituting a raw material containing a lower level of
mercury for a primary raw material with a higher level. We believe that
this beyond-the-floor option would be even less cost-effective than
either of the options discussed above, however. Given that sources are
sited near the supply of the primary raw material, transporting large
quantities of an alternate source of raw materials, even if available,
is likely to be cost-prohibitive, especially considering the small
expected emissions reductions that would result.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of mercury would be an appropriate
control option for sources. Two facilities typically burn hazardous
waste at a fuel replacement rate of 100%, while one facility has burned
a combination of fuel oil and natural gas in addition to the hazardous
waste. We considered switching only to natural gas as the auxiliary
fuel as a potential beyond-the-floor option. We do not believe that
switching to natural gas is a viable control option for the same
reasons discussed above for cement kilns.
For the reasons discussed above, we propose to establish the
emission standard for existing lightweight aggregate kilns at 67 [mu]g/
dscm. If we were to adopt such a standard, we are proposing that
sources comply with the standard on an annual basis because it is based
on normal emissions data.
[[Page 21266]]
3. What Is the Rationale for the MACT Floor for New Sources?
Mercury emissions from new lightweight aggregate kilns are
currently limited to 120 [mu]g/dscm by Sec. 63.1205(b)(2). This
standard was promulgated in the Interim Standards Rule (see 67 FR at
6797).
The MACT floor for new sources for mercury would be 67 [mu]g/dscm,
which considers emissions variability. This is an emission level that
the single best performing source identified with the SRE/Feed Approach
could be expected to achieve in 99 of 100 future tests when operating
under operating conditions identical to the compliance test conditions
during which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same three potential beyond-the-floor techniques
for control of mercury: (1) Use of activated carbon; (2) control of
mercury in the hazardous waste feed; and (3) control of the mercury in
the raw materials and auxiliary fuels.
Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. We made a conservative assumption that the use of activated
carbon injection will provide 70% mercury control and evaluated a
beyond-the-floor level of 20 [mu]g/dscm. The incremental annualized
compliance cost for a new lightweight aggregate kiln with average gas
flow rate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $0.26 million and would provide
an incremental reduction in mercury emissions of approximately 42
pounds per year. Nonair quality health and environmental impacts and
energy effects are accounted for in the national annualized compliance
cost estimates. Therefore, based on these factors and costs of $12
million per ton of mercury removed, we are not proposing a beyond-the-
floor standard based on activated carbon injection for new sources.
Feed Control of Mercury in the Hazardous Waste. We also believe
that the expense for further reduction in mercury emissions based on
further control of mercury concentrations in the hazardous waste is not
warranted. A beyond-the-floor level of 54 [mu]g/dscm, which represents
a 20% reduction from the floor level, would result in little additional
mercury reductions. For similar reasons discussed above for existing
sources, we conclude that a beyond-the-floor standard based on
controlling the mercury in the hazardous waste feed would not be
justified because of the costs coupled with estimated emission
reductions.
Feed Control of Mercury in the Raw Materials and Auxiliary Fuels.
Lightweight aggregate kilns could achieve a reduction in mercury
emissions by substituting a raw material containing lower levels of
mercury for a primary raw material with a higher level. For a new
source at an existing lightweight aggregate plant, we believe that this
beyond-the-floor option would not be cost-effective due to the costs of
transporting large quantities of an alternate source of raw materials
to the facility. Given that the plant site already exists and sited
near the source of raw material, replacing the raw materials at the
plant site with lower mercury-containing materials would be the
source's only option. For a new lightweight aggregate kiln constructed
at a new site--a greenfield site \117\--we are not aware of any
information and data from a source that has undertaken or is currently
located at a site whose raw materials are low in mercury which would
consistently decrease mercury emissions. Further, we are uncertain as
to what beyond-the-floor standard would be achievable using a lower, if
it exists, mercury-containing raw material. Although we are doubtful
that selecting a new plant site based on the content of metals in the
raw material is a realistic beyond-the-floor option considering the
numerous additional factors that go into such a decision, we solicit
comment on whether and what level of a beyond-the-floor standard based
on controlling the level of mercury in the raw materials is
appropriate.
---------------------------------------------------------------------------
\117\ A greenfield source is a kiln constructed at a site where
no lightweight aggregate kiln previously existed; however, a newly
constructed or reconstructed kiln at an existing site would not be
considered as a greenfield kiln.
---------------------------------------------------------------------------
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of mercury would be an appropriate
control option for sources. We considered using natural gas in lieu of
a fuel containing higher concentrations of mercury as a potential
beyond-the-floor option. As discussed for existing sources, we are
concerned about the availability of the natural gas infrastructure in
all regions of the United States and believe that using natural gas
would not be a viable control option for all new sources. Therefore, we
are not proposing a beyond-the-floor standard based on limiting mercury
in the raw material feed and auxiliary fuels.
Therefore, we propose a mercury standard of 67 [mu]g/dscm for new
sources. If we were to adopt such a standard, we are proposing that
sources comply with the standard on an annual basis because it is based
on normal emissions data.
C. What Are the Proposed Standards for Particulate Matter?
We are proposing to establish standards for existing and new
lightweight aggregate kilns that limit emissions of particulate matter
to 0.025 and 0.0099 gr/dscf, respectively. This standard would control
unenumerated HAP metals in hazardous waste, and all non-Hg HAP metals
in the raw material and fossil fuel inputs to the kiln.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Particulate matter emissions for existing lightweight aggregate
kilns are currently limited to 0.025 gr/dscf (57 mg/dscm) by Sec.
63.1205(a)(7). This standard was promulgated in the Interim Standards
Rule (See 67 FR at 6797). The particulate matter standard is a
surrogate control for the non-mercury metal HAP. All lightweight
aggregate kilns control particulate matter with baghouses.
We have compliance test emissions data for all lightweight
aggregate kiln sources. For most sources, we have compliance test
emissions data from more than one compliance test campaign. Our
database of particulate matter stack emissions range from 0.001 to
0.042 gr/dscf.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
APCD Approach. The calculated floor is 0.029 gr/dscf, which considers
emissions variability. This is an emission level that the average of
the best performing sources could be expected to achieve in 99 of 100
future tests when operating under operating conditions identical to the
compliance test conditions during which the emissions data were
obtained. The calculated floor level of 0.029 gr/dscf is less stringent
than the interim standard of 0.025 gr/dscf, which is a regulatory limit
relevant in identifying the floor level (so as to avoid any backsliding
from a current level of performance achieved by all lightweight
aggregate kilns, and hence, the level of minimal stringency at which
EPA could calculate the MACT floor). Therefore, we are proposing the
floor level as the current emission standard of 0.025 gr/dscf. This
emission level is currently being achieved by all sources.
[[Page 21267]]
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated improved particulate matter control to achieve a
beyond-the-floor standard of 29 mg/dscm (0.013 gr/dscf). The national
incremental annualized compliance cost for lightweight aggregate kilns
to meet this beyond-the-floor level rather than comply with the floor
controls would be approximately $0.32 million and would provide an
incremental reduction in particulate matter emissions beyond the MACT
floor controls of 8.6 tons per year. Nonair quality health and
environmental impacts and energy effects were evaluated to estimate the
impacts between further improvements to control particulate matter and
controls likely to be used to meet the floor level. We estimate that
this beyond-the-floor option would increase the amount of solid waste
generated by 9 tons per year beyond the requirements to achieve the
floor level. Therefore, based on these factors and costs of
approximately $36,600 per additional ton of particulate matter removed,
we are not proposing a beyond-the-floor standard based on improved
particulate matter control.
3. What Is the Rationale for the MACT Floor for New Sources?
Particulate matter emissions from new lightweight aggregate kilns
are currently limited to 0.025 gr/dscf by Sec. 63.1205(b)(7). This
standard was promulgated in the Interim Standards Rule (See 67 FR at
6797, February 13, 2002).
The MACT floor for new sources for particulate matter would be 23
mg/dscm (0.0099 gr/dscf), which considers emissions variability. This
is an emission level that the single best performing source identified
with the APCD Approach could be expected to achieve in 99 of 100 future
tests when operating under operating conditions identical to the
compliance test conditions during which the emissions data were
obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated improved particulate matter control to achieve a
beyond-the-floor standard. We evaluated a beyond-the-floor level of 12
mg/dscm (0.005 gr/dscf). The incremental annualized compliance cost for
a new lightweight aggregate kiln with an average gas flow rate to meet
this beyond-the-floor level, rather than comply with the floor level,
would be approximately $91,400 million and would provide an incremental
reduction in particulate matter emissions of approximately 2 tons per
year. Nonair quality health and environmental impacts and energy
effects were also evaluated and are included in the cost estimates.
Therefore, based on these factors and costs of approximately $45,600
per additional ton of particulate removed, we are not proposing a
beyond-the-floor standard based on improved particulate matter control
for new lightweight aggregate kilns. Therefore, we propose a
particulate matter standard of 2.3 mg/dscm (0.0099 gr/dscf) for new
sources.
D. What Are the Proposed Standards for Semivolatile Metals?
We are proposing to establish standards for existing lightweight
aggregate kilns that limit emissions of semivolatile metals (cadmium
and lead, combined) to 3.1 x 10-4 lbs semivolatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste and 250 [mu]g/dscm. The proposed standard
for new sources is 2.4 x 10-5 lbs semivolatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste and 43 [mu]g/dscm.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Semivolatile metals emissions from existing lightweight aggregate
kilns are currently limited to 250 [mu]g/dscm by Sec. 63.1205(a)(3).
This standard was promulgated in the Interim Standards Rule (See 67 FR
at 6797). Lightweight aggregate kilns control emissions of semivolatile
metals with baghouses and/or by controlling the feed concentration of
semivolatile metals in the hazardous waste.
We have compliance test emissions data for all lightweight
aggregate kiln sources. For most sources, we have compliance test
emissions data from more than one compliance test campaign.
Semivolatile metal stack emissions range from approximately 1 to over
1,600 [mu]g/dscm. These emissions are expressed as mass of semivolatile
metals (from all feedstocks) per unit volume of stack gas. Hazardous
waste thermal emissions range from 3.0 x 10-6 to 1.1 x
10-3 lbs per million Btu. Hazardous waste thermal emissions
represent the mass of semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste. For
most lightweight aggregate kilns, lead was the major contributor to
semivolatile emissions.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 3.1 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which considers
emissions variability. This is an emission level that the average of
the best performing sources could be expected to achieve in 99 of 100
future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 71%
of sources, and would reduce semivolatile metals emissions by 30 pounds
per year.
To put the proposed floor level in context for a hypothetical
lightweight aggregate kiln that gets 90% of its required heat input
from hazardous waste, a thermal emissions level of 3.1 x
10-4 lbs semivolatile metals attributable to the hazardous
waste per million Btu heat input of the hazardous waste equates
approximately to a stack gas concentration of 300 [mu]g/dscm. This
estimated stack gas concentration does not include contributions to
emission from other semivolatile metals-containing materials such as
raw materials and fossil fuels. The additional contribution to stack
emissions of semivolatile metals in an average raw material is
estimated to range as high as 20 to 50 [mu]g/dscm. Thus, for the
hypothetical lightweight aggregate kiln the thermal emissions floor
level of 3.1 x 10-4 lbs semivolatile metals attributable to
the hazardous waste per million Btu heat input of the hazardous waste
is estimated to be less than 350 [mu]g/dscm, which is higher than the
current interim standard of 250 [mu]g/dscm. Given that comparing the
proposed floor level to the interim standard requires numerous
assumptions (as just illustrated) including hazardous waste fuel
replacement rates, heat input requirements per ton of clinker,
concentrations of semivolatile metals in the raw material and fuels,
and system removal efficiency, we have included a more detailed
analysis in the background document.\118\ Our detailed analysis
indicates the proposed floor level could be less stringent than the
interim standard for some sources. In order to avoid any backsliding
from the current level of performance achieved by all lightweight
aggregate kilns, we propose a dual standard: the semivolatile metals
standard as both the
[[Page 21268]]
calculated floor level, expressed as a hazardous waste thermal
emissions level, and the current interim standard. This would ensure
that all sources are complying with a limit that is at least as
stringent as the interim standard.
---------------------------------------------------------------------------
\118\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 23.
---------------------------------------------------------------------------
In the September 1999 final rule, we acknowledged that a
lightweight aggregate kiln using properly designed and operated MACT
control technologies, including controlling the levels of metals in the
hazardous waste, may not be capable of achieving a given emission
standard because of mineral and process raw material contributions that
might cause an exceedance of the emission standard. To address this
concern, we promulgated a provision that allows kilns to petition for
alternative standards provided that they submit site-specific
information that shows raw material hazardous air pollutant
contributions to the emissions prevent the source from complying with
the emission standard even though the kiln is using MACT control. See
Sec. 63.1206(b)(9). If we were to adopt the proposed dual semivolatile
(and low volatile) metals standards approach, we propose to retain the
alternative standard provisions under Sec. 63.1206(b)(9) for
semivolatile metals (and low volatile metals). We invite comment on
this approach.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of semivolatile metals: (1) Improved particulate matter
control; (2) control of semivolatile metals in the hazardous waste
feed; and (3) control of the semivolatile metals in the raw materials
and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of semivolatile metals. Our data show that all
lightweight aggregate kilns are already achieving greater than 99.7%
system removal efficiency for semivolatile metals, with many attaining
99.9% removal. Thus, additional control of particulate matter are
likely to result in only modest additional reductions of semivolatile
metals emissions. We evaluated a beyond-the-floor level of 1.5 x
10-4 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste,
which represents a 50% reduction in emissions from MACT floor levels.
The national incremental annualized compliance cost for lightweight
aggregate kilns to meet this beyond-the-floor level rather than to
comply with the floor controls would be approximately $84,200 and would
provide an incremental reduction in semivolatile metals emissions
beyond the MACT floor controls of 20 pounds per year. Nonair quality
health and environmental impacts and energy effects were evaluated to
estimate the impacts between further improvements to control
particulate matter and controls likely to be used to meet the floor
level. We estimate that this beyond-the-floor option would increase the
amount of solid waste generated by less than 10 tons per year and would
also require sources to use an additional 2,000 kW-hours per year
beyond the requirements to achieve the floor level. The costs
associated with these impacts are accounted for in the national
annualized compliance cost estimates. Therefore, based on these factors
and costs of approximately $7.6 million per additional ton of
semivolatile metals removed, we are not proposing a beyond-the-floor
standard based on improved particulate matter control.n
Feed Control of Semivolatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 2.5 x 10-4 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
semivolatile metals in hazardous waste can be used and still achieve
appreciable emissions reductions. The national incremental annualized
compliance cost for lightweight aggregate kilns to meet this beyond-
the-floor level rather than comply with the floor controls would be
approximately $6,000 and would provide an incremental reduction in
semivolatile metals emissions beyond the MACT floor controls of less
than one pound per year. Nonair quality health and environmental
impacts and energy effects were evaluated and are included in the
national compliance cost estimates. Therefore, based on these factors
and costs of approximately $20 million per additional ton of
semivolatile metals removed, we are not proposing a beyond-the-floor
standard based on feed control of semivolatile metals in the hazardous
waste.
Feed Control of Semivolatile Metals in the Raw Materials and
Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction
in semivolatile metal emissions by substituting a raw material
containing lower levels of cadmium and/or lead for a primary raw
material with higher levels of these metals. We believe that this
beyond-the-floor option would even be less cost-effective than either
of the options discussed above, however. Given that facilities are
sited near the primary raw material supply, acquiring and transporting
large quantities of an alternate source of raw materials is likely to
be cost-prohibitive. Therefore, we are not proposing a beyond-the-floor
standard based on limiting semivolatile metals in the raw material
feed.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of semivolatile metals would be an
appropriate control option for sources. Two facilities typically burn
hazardous waste at a fuel replacement rate of 100%, while one facility
has burned a combination of fuel oil and natural gas in addition to the
hazardous waste. We considered switching only to natural gas as the
auxiliary fuel as a potential beyond-the-floor option. We do not
believe that switching to natural gas is a viable control option for
similar reasons discussed above for cement kilns.
For the reasons discussed above, we propose to establish the
emission standard for existing lightweight aggregate kilns at 3.1 x
10-4 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste and
250 [mu]g/dscm.
3. What Is the Rationale for the MACT Floor for New Sources?
Semivolatile metals emissions from new lightweight aggregate kilns
are currently limited to 43 [mu]g/dscm by Sec. 63.1205(b)(3). This
standard was promulgated in the Interim Standards Rule (See 67 FR at
6797).
The MACT floor for new sources for semivolatile metals would be 2.4
x 10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu in the hazardous waste, which considers
emissions variability. This is an emission level that the single best
performing source identified with the SRE/Feed Approach could be
expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained.
To put the proposed floor level in context for a hypothetical
lightweight aggregate kiln that gets 90% of its required heat input
from hazardous waste, a thermal emissions level of 2.4 x
10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste can
equate to a stack gas concentration as high as 60 [mu]g/dscm, including
contributions from typical raw materials. Thus, for the
[[Page 21269]]
hypothetical lightweight aggregate kiln the thermal emissions floor
level of 2.4 x 10-5 lbs semivolatile metals emissions
attributable to the hazardous waste per million Btu heat input of the
hazardous waste is estimated to be as high as 60 [mu]g/dscm, which is
higher than the current interim standard of 43 [mu]g/dscm. In order to
avoid any backsliding from the current level of performance for a new
lightweight aggregate kiln source, we propose a dual standard: the
semivolatile metals standard as both the calculated floor level,
expressed as a hazardous waste thermal emissions level, and the current
interim standard. This would ensure that all sources are complying with
a limit that is at least as stringent as the interim standard. Thus,
the proposed MACT floor for new lightweight aggregate kilns is 2.4 x
10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste and
43 [mu]g/dscm.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same three potential beyond-the-floor techniques
for control of semivolatile metals: (1) Improved control of particulate
matter; (2) control of semivolatile metals in the hazardous waste feed;
and (3) control of semivolatile metals in the raw materials and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of semivolatile metals. We evaluated improved
control of particulate matter based on a state-of-the-art baghouse
using a high quality fabric filter bag material as beyond-the-floor
control for further reductions in semivolatile metals emissions. We
evaluated a beyond-the-floor level of 1.2 x 10-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste. The incremental
annualized compliance cost for a new lightweight aggregate kiln with
average gas flowrate to meet this beyond-the-floor level, rather than
to comply with the floor level, would be approximately $0.11 million
and would provide an incremental reduction in semivolatile metals
emissions of approximately 13 pounds per year. Nonair quality health
and environmental impacts and energy effects were evaluated and are
included in the cost estimates. We estimate that this beyond-the-floor
option would increase the amount of solid waste generated by 3 tons per
year and would also require sources to use an additional 0.3 million
kW-hours per year beyond the requirements to achieve the floor level.
Therefore, based on these factors and costs of approximately $18
million per ton of semivolatile metals removed, we are not proposing a
beyond-the-floor standard based on improved particulate matter control
for new lightweight aggregate kilns.
Feed Control of Semivolatile Metals in the Hazardous Waste. We also
believe that the expense for further reduction in semivolatile metals
emissions based on further control of semivolatile metals
concentrations in the hazardous waste is not warranted. We considered a
beyond-the-floor level of 1.9 x 10-5 lbs semivolatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste, which represents a 20% reduction from the
floor level. Nonair quality health and environmental impacts and energy
effects were evaluated and are included in the compliance cost
estimates. For similar reasons discussed above for existing sources, we
conclude that a beyond-the-floor standard based on controlling the
concentration of semivolatile metals levels in the hazardous waste feed
would not be justified because of the costs and estimated emission
reductions.
Feed Control of Semivolatile Metals in the Raw Materials and
Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction
in semivolatile metals emissions by substituting a raw material
containing lower levels of cadmium and lead for a primary raw material
with a higher level. For a new source at an existing facility, we
believe that this beyond-the-floor option would not be cost-effective
due to the costs of transporting large quantities of an alternate
source of raw material to the facility. Given that the plant site
already exists and is sited near the source of raw material, replacing
the raw materials at the plant site with lower semivolatile metals-
containing materials would be the source's only option. For a kiln
constructed at a new greenfield site, we are not aware of any
information and data from a source that has undertaken or is currently
located at a site whose raw materials are inherently lower in
semivolatile metals that would consistently achieve reduced
semivolatile metals emissions. Further, we are uncertain as to what
beyond-the-floor standard would be achievable using, if it exists, a
lower semivolatile metals-containing raw material. Although we are
doubtful that selecting a new plant site based on the content of metals
in the raw material is a realistic beyond-the-floor option considering
the numerous additional factors that go into such a decision, we
solicit comment on whether and what level of a beyond-the-floor
standard based on controlling the level of semivolatile metals in the
raw materials is appropriate.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of semivolatile metals would be an
appropriate control option for sources. Two facilities typically burn
hazardous waste at a fuel replacement rate of 100%, while one facility
has burned a combination of fuel oil and natural gas in addition to the
hazardous waste. We considered switching only to natural gas as the
auxiliary fuel as a potential beyond-the-floor option. We do not
believe that switching to natural gas is a viable control option for
the same reasons discussed above for cement kilns.
For the reasons discussed above, we propose to establish the
emission standard for new lightweight aggregate kilns at 2.4 x
10-5 lbs semivolatile metals emissions attributable to the
hazardous waste per million Btu heat content in the hazardous waste and
43 [mu]g/dscm.
E. What Are the Proposed Standards for Low Volatile Metals?
We are proposing to establish standards for existing lightweight
aggregate kilns that limit emissions of low volatile metals (arsenic,
beryllium, and chromium) to 9.5 x 10-5 lbs low volatile
metals emissions attributable to the hazardous waste per million Btu
heat input of the hazardous waste and 110 [mu]g/dscm. The proposed
standard for new sources is 3.2 x 10-5 lbs low volatile
metals emissions attributable to the hazardous waste per million Btu
heat input of the hazardous waste and 110 [mu]g/dscm.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Low volatile metals emissions from existing lightweight aggregate
kilns are currently limited to 110 [mu]g/dscm by Sec. 63.1205(a)(4).
This standard was promulgated in the Interim Standards Rule (see 67 FR
at 6797). Lightweight aggregate kilns control emissions of low volatile
metals with baghouses and/or by controlling the feed concentration of
low volatile metals in the hazardous waste.
We have compliance test emissions data for all lightweight
aggregate kiln sources. For most sources, we have compliance test
emissions data from more than one compliance test campaign. Low
volatile metal stack emissions range from approximately 16 to 200
[mu]g/dscm. These emissions are expressed as mass of low volatile
metals (from all feedstocks) per unit volume of
[[Page 21270]]
stack gas. Hazardous waste thermal emissions range from 9.7 x
10-6 to 1.8 x 10-4 lbs per million Btu. Hazardous
waste thermal emissions represent the mass of low volatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste. For most lightweight aggregate kilns,
chromium was the major contributor to low volatile emissions.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 9.5 x 10-5 lbs
low volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which considers
emissions variability. This is an emission level that the average of
the best performing sources could be expected to achieve in 99 of 100
future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 57%
of sources and would reduce low volatile metals emissions by 30 pounds
per year.
To put the proposed floor level in context for a hypothetical
lightweight aggregate kiln that gets 90% of its required heat input
from hazardous waste, a thermal emissions level of 9.5 x
10-5 lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste
equates approximately to a stack gas concentration of 90 [mu]g/dscm.
This estimated stack gas concentration does not include contributions
to emission from other low volatile metals-containing materials such as
raw materials. The additional contribution to stack emissions of low
volatile metals in an average raw material is estimated to be 50 [mu]g/
dscm. Thus, for the hypothetical lightweight aggregate kiln the thermal
emissions floor level of 9.5 x 10-5 lbs low volatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste is estimated to be 150 [mu]g/dscm, which
is higher than the current interim standard of 110 [mu]g/dscm. Given
that comparing the proposed floor level to the interim standard
requires numerous assumptions including hazardous waste fuel
replacement rates, heat input requirements per ton of clinker,
concentrations of low volatile metals in the raw material and fuels,
and system removal efficiency, we have included a more detailed
analysis in the background document.\119\ Our detailed analysis
indicates the proposed floor level could be less stringent than the
interim standard for some sources. In order to avoid any backsliding
from the current level of performance achieved by all lightweight
aggregate kilns, we propose a dual standard: the low volatile metals
standard as both the calculated floor level, expressed as a hazardous
waste thermal emissions level, and the current interim standard. This
would ensure that all sources are complying with a limit that is at
least as stringent as the interim standard.
---------------------------------------------------------------------------
\119\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 23.
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified three potential beyond-the-floor techniques for
control of low volatile metals: (1) Improved particulate matter
control; (2) control of low volatile metals in the hazardous waste
feed; and (3) control of the low volatile metals in the raw materials
and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of low volatile metals. Our data show that all
lightweight aggregate kilns are already achieving greater than 99.8%
system removal efficiency for low volatile metals, with many attaining
99.9% or greater removal. Thus, additional control of particulate
matter emissions is likely to result in only a small increment in
reduction of low volatile metals emissions. We evaluated a beyond-the-
floor level of 4.7 x 10-5 lbs low volatile metals emissions
attributable to the hazardous waste per million Btu heat input of the
hazardous waste. The national incremental annualized compliance cost
for lightweight aggregate kilns to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $0.24
million and would provide an incremental reduction in low volatile
metals emissions beyond the MACT floor controls of 28 pounds per year.
Nonair quality health and environmental impacts and energy effects were
evaluated to estimate the impacts between further improvements to
control particulate matter and controls likely to be used to meet the
floor level. We estimate that this beyond-the-floor option would
increase the amount of solid waste generated by less than 30 tons per
year and would also require sources to use an additional 46,000 kW-
hours of energy per year. Therefore, based on these factors and costs
of approximately $17 million per additional ton of low volatile metals
removed, we are not proposing a beyond-the-floor standard based on
improved particulate matter control.
Feed Control of Low Volatile Metals in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 7.6 x 10-5 lbs low
volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste, which represents a 20%
reduction from the floor level. We chose a 20% reduction as a level
representing the practicable extent that additional feedrate control of
low volatile metals in hazardous waste (beyond feedrate control that
may be necessary to achieve the floor level) can be used and still
achieve modest emissions reductions. The national incremental
annualized compliance cost for lightweight aggregate kilns to meet this
beyond-the-floor level rather than comply with the floor controls would
be approximately $150,000 and would provide an incremental reduction in
low volatile metals emissions beyond the MACT floor controls of 14
pounds per year. Nonair quality health and environmental impacts and
energy effects were considered and are included in the cost estimates.
Therefore, based on these factors and costs of approximately $22
million per additional ton of low volatile metals removed, we are not
proposing a beyond-the-floor standard based on feed control of low
volatile metals in the hazardous waste.
Feed Control of Low Volatile Metals in the Raw Materials and
Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction
in low volatile metal emissions by substituting a raw material
containing lower levels of arsenic, beryllium, and/or chromium for a
primary raw material with higher levels of these metals. We believe
that this beyond-the-floor option would even be less cost-effective
than either of the options discussed above, however. Given that
facilities are sited near the primary raw material supply, acquiring
and transporting large quantities of an alternate source of raw
materials is likely to be cost-prohibitive. Therefore, we are not
proposing a beyond-the-floor standard based on limiting low volatile
metals in the raw material feed.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of low volatile metals would be an
appropriate control option for sources. Two facilities typically burn
hazardous waste at a fuel replacement rate of 100%, while one facility
has burned a combination of fuel oil and natural gas in addition to the
hazardous waste. We considered switching only to natural gas as the
auxiliary fuel as a potential beyond-the-
[[Page 21271]]
floor option. We do not believe that switching to natural gas is a
viable control option for similar reasons discussed above for cement
kilns.
For the reasons discussed above, we propose to establish the
emission standard for existing lightweight aggregate kilns at 9.5 x
10-5 lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste and
110 [mu]g/dscm.
3. What Is the Rationale for the MACT Floor for New Sources?
Low volatile metals emissions from new lightweight aggregate kilns
are currently limited to 110 [mu]g/dscm by Sec. 63.1205(b)(4). This
standard was promulgated in the Interim Standards Rule (See 67 FR at
6797).
The MACT floor for new sources for low volatile metals would be 3.2
x 10-5 lbs low volatile metals emissions in the hazardous
waste per million Btu in the hazardous waste, which considers emissions
variability. This is an emission level that the single best performing
source identified with the SRE/Feed Approach could be expected to
achieve in 99 of 100 future tests when operating under operating
conditions identical to the compliance test conditions during which the
emissions data were obtained.
As discussed for existing sources, in order to avoid any
backsliding from the current level of performance for a new lightweight
aggregate kiln source, we propose a dual standard: the low volatile
metals standard as both the calculated floor level, expressed as a
hazardous waste thermal emissions level, and the current interim
standard. This would ensure that all sources are complying with a limit
that is at least as stringent as the interim standard. Thus, the
proposed MACT floor for new lightweight aggregate kilns is 3.2 x
10-5 lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat input of the hazardous waste and
110 [mu]g/dscm.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We considered three potential beyond-the-floor techniques for
control of low volatile metals: (1) Improved particulate matter
control; (2) control of low volatile metals in the hazardous waste
feed; and (3) control of the low volatile metals in the raw materials
and fuels.
Improved Particulate Matter Control. Controlling particulate matter
also controls emissions of low volatile metals. We evaluated improved
control of particulate matter based on a state-of-the-art baghouse
using a high quality fabric filter bag material as beyond-the-floor
control for further reductions in low volatile metals emissions. We
evaluated a beyond-the-floor level of 1.6 x 10-5 lbs low
volatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste. The incremental
annualized compliance cost for a new lightweight aggregate kiln with
average gas flowrate to meet this beyond-the-floor level, rather than
to comply with the floor level, would be approximately $0.11 million
and would provide an incremental reduction in low volatile metals
emissions of approximately 16 pounds per year. Nonair quality health
and environmental impacts and energy effects were evaluated and are
included in the cost estimates. We estimate that this beyond-the-floor
option would increase the amount of solid waste generated by 3 tons per
year and would also require sources to use an additional 0.3 million
kW-hours per year beyond the requirements to achieve the floor level.
Therefore, based on these factors and costs of nearly $14 million per
ton of low volatile metals removed, we are not proposing a beyond-the-
floor standard based on improved particulate matter control for new
lightweight aggregate kilns.
Feed Control of Low Volatile Metals in the Hazardous Waste. We also
believe that the expense for further reduction in low volatile metals
emissions based on further control of low volatile metals
concentrations in the hazardous waste is not warranted. We considered a
beyond-the-floor level of 2.6 x 10-5 lbs low volatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste, which represents a 20% reduction from the
floor level. Nonair quality health and environmental impacts and energy
effects were evaluated and are included in the compliance cost
estimates. For similar reasons discussed above for existing sources, we
conclude that a beyond-the-floor standard based on controlling the
concentration of low volatile metals levels in the hazardous waste feed
would not be justified because of the costs and estimated emission
reductions.
Feed Control of Low Volatile Metals in the Raw Materials and
Auxiliary Fuels. Lightweight aggregate kilns could achieve a reduction
in low volatile metals emissions by substituting a raw material
containing lower levels of arsenic, beryllium, and/or chromium for a
primary raw material with a higher level. For a new source at an
existing facility, we believe that this beyond-the-floor option would
not be cost-effective due to the costs of transporting large quantities
of an alternate source of raw material to the facility. Given that the
plant site already exists and is sited near the source of raw material,
replacing the raw materials at the plant site with lower low volatile
metals-containing materials would be the source's only option. For a
kiln constructed at a new greenfield site, we are not aware of any
information and data from a source that has undertaken or is currently
located at a site whose raw materials are inherently lower in low
volatile metals that would consistently achieve reduced low volatile
metals emissions. Further, we are uncertain as to what beyond-the-floor
standard would be achievable using, if it exists, a lower low volatile
metals-containing raw material. Although we are doubtful that selecting
a new plant site based on the content of metals in the raw material is
a realistic beyond-the-floor option considering the numerous additional
factors that go into such a decision, we solicit comment on whether and
what level of a beyond-the-floor standard based on controlling the
level of low volatile metals in the raw materials is appropriate.
We also considered whether fuel switching to an auxiliary fuel
containing a lower concentration of low volatile metals would be an
appropriate control option for sources. Two facilities typically burn
hazardous waste at a fuel replacement rate of 100%, while one facility
has burned a combination of fuel oil and natural gas in addition to the
hazardous waste. We considered switching only to natural gas as the
auxiliary fuel as a potential beyond-the-floor option. We do not
believe that switching to natural gas is a viable control option for
the same reasons discussed above for cement kilns.
For the reasons discussed above, we propose to establish the
emission standard for new lightweight aggregate kilns at 3.2 x
10-\5\ lbs low volatile metals emissions attributable to the
hazardous waste per million Btu heat content in the hazardous waste and
110 [mu]g/dscm.
F. What Are the Proposed Standards for Hydrogen Chloride and Chlorine
Gas?
We are proposing to establish standards for existing and new
lightweight aggregate kilns that limit total chlorine emissions
(hydrogen chloride and chlorine gas, combined, reported as a chloride
equivalent) to 600 ppmv. Although we are also proposing to invoke CAA
section 112(d)(4) to establish alternative risk-based standards in lieu
of the MACT emission standards for total chlorine, the risk-based
standards would be capped at the
[[Page 21272]]
interim standards. Given that we are proposing MACT standards
equivalent to the interim standards--600 ppmv, an emission level you
are currently achieving--you would not be eligible for the section
112(d)(4) risk-based standards. See Part Two, Section XIII for
additional details.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Total chlorine emissions from existing cement kilns are limited to
600 ppmv by Sec. 63.1205(a)(6). This standard was promulgated in the
Interim Standards Rule (See 67 FR at 6797). One of the three
lightweight aggregate facilities uses a venturi scrubber to remove
total chlorine from the gas stream. The system removal efficiency (SRE)
achieved by this facility during compliance testing shows removal
efficiencies ranging from 96 to 99%. Sources at the other two
facilities do not use air pollution control equipment to capture
emissions of total chlorine, and, therefore, SREs are negligible.
The majority of the chlorine fed to the lightweight aggregate kiln
during a compliance test comes from the hazardous waste. In all but a
few cases the hazardous waste contribution to the total amount of
chlorine fed to the kiln represented at least 80% of the total loading
to the kiln. The proposed MACT floor control for total chlorine is, in
part, based on controlling the concentration of chlorine in the
hazardous waste. The chlorine concentration in the hazardous waste will
affect emissions of total chlorine at a given SRE because emissions
will increase as the chlorine loading increases.
We have compliance test emissions data for all lightweight
aggregate kiln sources. For most sources, we have compliance test
emissions data from more than one compliance test campaign. Total
chlorine emissions range from 14 to 116 ppmv for the source using a
venturi scrubber and range from 500 to 2,400 ppmv at sources without
scrubbing control equipment.
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 3.0 lbs total chlorine
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste, which considers emissions variability.
This is an emission level that the average of the best performing
sources could be expected to achieve in 99 of 100 future tests when
operating under conditions identical to the compliance test conditions
during which the emissions data were obtained.
To put the proposed floor level in context for a hypothetical
lightweight aggregate kiln that gets 90% of its required heat input
from hazardous waste, a thermal emissions level of 3.0 lbs total
chlorine emissions attributable to the hazardous waste per million Btu
heat input of the hazardous waste equates approximately to a stack gas
concentration of 1,970 ppmv. This estimated stack gas concentration
does not include contributions to emission from other chlorine-
containing materials such as raw materials. Given that the calculated
floor level is less stringent than the current interim emission
standard of 600 ppmv. In order to avoid any backsliding from the
current level of performance achieved by all lightweight aggregate
kilns, we are proposing the floor standard as the current emission
standard of 600 ppmv. This emission level is currently being achieved
by all sources.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered a beyond-the-floor standard of 150 ppmv based on the
assumption that dry lime scrubbing will provide 75% control of hydrogen
chloride.\120\ In addition, for costing purposes we assumed that
lightweight aggregate kilns needing total chlorine reductions to
achieve the beyond-the-floor level would install the dry scrubbing
system after the existing particulate matter control device and add a
new, smaller baghouse to remove the products of the reaction and any
unreacted lime. We chose this conservative costing approach to address
potential concerns that unreacted lime and collected chloride and
sulfur salts may interfere with lightweight aggregate dust use
practices.
---------------------------------------------------------------------------
\120\ We also considered controlling the chlorine levels in the
hazardous waste feed and controlling the chlorine levels in the raw
materials as potential beyond-the-floor techniques; however, it is
our judgment that they are not likely to be as cost-effective as dry
lime scrubbing.
---------------------------------------------------------------------------
The national incremental annualized compliance cost for lightweight
aggregate kilns to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $1.9 million and would
provide an incremental reduction in total chlorine emissions beyond the
MACT floor controls of 280 tons per year, for a cost-effectiveness of
$6,800 per additional ton of total chlorine removed. We evaluated
nonair quality health and environmental impacts and energy effects
associated with this beyond-the-floor standard and estimate that this
beyond-the-floor option would increase the amount of solid waste
generated by 12,700 tons per year and would also require sources to use
an additional 175,000 kW-hours per year and 31 million gallons of water
beyond the requirements to achieve the floor level.
We note that a cost of $6,800 per additional ton of total chlorine
removed is in the ``grey area'' between a cost the Agency has concluded
is cost-effective and a cost the Agency has concluded is not cost-
effective under other MACT rules. EPA concluded that a cost of $1,100
per ton of total chlorine removed for hazardous waste burning
lightweight aggregate kilns was cost-effective in the 1999 MACT final
rule. See 68 FR at 52900. EPA concluded, however, that a cost of
$45,000 per ton of hydrogen chloride removed was not cost-effective for
industrial boilers. See 68 FR at 1677. Consequently, we are concerned
that a cost of $6,800 per additional ton of total chlorine removed is
not warranted. Therefore, after considering cost-effectiveness and
nonair quality health and environmental impacts and energy effects, we
are not proposing a beyond-the-floor standard.
We specifically request comment on whether a beyond-the-floor
standard is warranted.
3. What Is the Rationale for the MACT Floor for New Sources?
Total chlorine emissions from new lightweight aggregate kilns are
currently limited to 600 ppmv by Sec. 63.1205(b)(6). This standard was
promulgated in the Interim Standards Rule (See 67 FR at 6797). The MACT
floor for new sources for total chlorine would be 0.93 lbs chlorine in
the hazardous waste per million Btu in the hazardous waste, which
considers emissions variability.
To put the proposed floor level in context for a hypothetical
lightweight aggregate kiln that gets 90% of its required heat input
from hazardous waste, a thermal emissions level of 0.93 lbs total
chlorine emissions attributable to the hazardous waste per million Btu
heat input of the hazardous waste equates approximately to a stack gas
concentration of 610 ppmv. This estimated stack gas concentration does
not include contributions to emission from other chlorine-containing
materials such as raw materials. Given that the calculated floor level
is less stringent than the current interim emission standard of 600
ppmv. In order to avoid any backsliding from the current standard for a
new lightweight aggregate kilns, we are proposing the floor standard as
the current emission standard of 600 ppmv.
[[Page 21273]]
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
Similar to existing sources, we considered a beyond-the-floor
standard of 150 ppmv based on the assumption that dry lime scrubbing
will provide 75% control of hydrogen chloride. The incremental
annualized compliance cost for a new lightweight aggregate kiln with
average gas flowrate to meet this beyond-the-floor level, rather than
to comply with the floor level, would be approximately $0.42 million
and would provide an incremental reduction in total chlorine emissions
of approximately 150 tons per year for a cost-effectiveness of
approximately $2,800 per additional ton of total chlorine removed.
Nonair quality health and environmental impacts and energy effects were
evaluated and are included in the cost estimates. We estimate that this
beyond-the-floor option would increase the amount of solid waste
generated by 23 tons per year and would also require sources to use an
additional 0.3 million kW-hours per year and 2 million gallons of water
beyond the requirements to achieve the floor level.
A cost of $2,800 per additional ton of total chlorine removed is in
the ``grey area'' between a cost the Agency has concluded is cost-
effective and a cost the Agency has concluded is not cost-effective
under other MACT rules, as discussed above. Therefore, we are concerned
that a cost-effectiveness of $2,800 per additional ton of total
chlorine removed may not be warranted. After considering cost-
effectiveness and nonair quality health and environmental impacts and
energy effects, we are not proposing a beyond-the-floor standard.
We specifically request comment on whether a beyond-the-floor
standard is warranted.
G. What Are the Standards for Hydrocarbons and Carbon Monoxide?
Hydrocarbon and carbon monoxide standards are surrogates to control
emissions of organic hazardous air pollutants for existing and new
lightweight aggregate kilns. The standards limit hydrocarbons and
carbon monoxide concentrations to 20 ppmv or 100 ppmv. See Sec. Sec.
63.1205(a)(5) and (b)(5). Existing and new lightweight aggregate kilns
can elect to comply with either the hydrocarbon limit or the carbon
monoxide limit on a continuous basis. Sources that comply with the
carbon monoxide limit on a continuous basis must also demonstrate
compliance with the hydrocarbon standard during the comprehensive
performance test. However, continuous hydrocarbon monitoring following
the performance test is not required. The rationale for these decisions
are discussed in the September 1999 final rule (64 FR at 52900). We
view the standards for hydrocarbons and carbon monoxide as unaffected
by the Court's vacature of the challenged regulations in its decision
of July 24, 2001. We therefore are not proposing these standards for
lightweight aggregate kilns, but rather are mentioning them here for
the reader's convenience.
H. What Are the Standards for Destruction and Removal Efficiency?
The destruction and removal efficiency (DRE) standard is a
surrogate to control emissions of organic hazardous air pollutants
other than dioxin/furans. The standard for existing and new lightweight
aggregate kilns requires 99.99% DRE for each principal organic
hazardous constituent, except that 99.9999% DRE is required if
specified dioxin-listed hazardous wastes are burned. See Sec. Sec.
63.1205(c). The rationale for these decisions are discussed in the
September 1999 final rule (64 FR at 52902). We view the standards for
DRE as unaffected by the Court's vacature of the challenged regulations
in its decision of July 24, 2001. We therefore are not proposing these
standards for lightweight aggregate kilns, but rather are mentioning
them here for the reader's convenience.
X. How Did EPA Determine the Proposed Emission Standards for Hazardous
Waste Burning Solid Fuel-Fired Boilers?
The proposed standards for existing and new solid fuel-fired
boilers that burn hazardous waste are summarized in the table below.
See proposed Sec. 63.1216.
Proposed Standards for Existing and New Solid Fuel-Fired Boilers
------------------------------------------------------------------------
Emission standard \1\
Hazardous air pollutant or -------------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan............ 100 ppmv carbon 100 ppmv carbon
monoxide or 10 ppmv monoxide or 10 ppmv
hydrocarbons.. hydrocarbons.
Mercury..................... 10 [mu]g/dscm....... 10 [mu]g/dscm.
Particulate matter.......... 69 mg/dscm (0.030 gr/ 34 mg/dscm (0.015 gr/
dscf). dscf).
Semivolatile metals......... 170 [mu]g/dscm...... 170 [mu]g/dscm.
Low volatile metals......... 210 [mu]g/dscm...... 190 [mu]g/dscm.
Hydrogen chloride and 440 ppmv or the 73 ppmv or the
chlorine gas \2\. alternative alternative
emission limits emission limits
under Sec. under Sec.
63.1215. 63.1215.
Carbon monoxide or 100 ppmv carbon 100 ppmv carbon
hydrocarbons \3\. monoxide or 10 ppmv monoxide or 10 ppmv
hydrocarbons. hydrocarbons.
-----------------------------
Destruction and Removal For existing and new sources, 99.99% for
Efficiency. each principal organic hazardous
constituent (POHC). For sources burning
hazardous wastes F020, F021, F022, F023,
F026, or F027, however, 99.9999% for each
POHC.
------------------------------------------------------------------------
\1\ All emission standards are corrected to 7% oxygen, dry basis.
\2\ Combined standard, reported as a chloride (Cl(-)) equivalent.
\3\ Hourly rolling average. Hydrocarbons reported as propane.
We considered whether fuel switching could be considered a control
technology to achieve MACT floor control. We investigated whether fuel
switching would achieve lower HAP emissions and whether it could be
technically achieved considering the existing design of solid fuel-
fired boilers. We also considered the availability of various types of
fuel. After considering these factors, we determined that fuel
switching is not an appropriate control technology for purposes of
determining the MACT floor level of control. This decision is based on
the overall effect of fuel switching on HAP emissions, technical
[[Page 21274]]
and design considerations, and concerns about fuel availability.
We determined that while fuel switching from coal to natural gas or
oil would decrease particulate matter and some metal HAP emissions,
emissions of some organic HAP would increase, resulting in uncertain
benefits.\121\ We believe that it is inappropriate in a MACT rulemaking
to consider as MACT a control option that potentially will decrease
emissions of one HAP while increasing emissions of another HAP. In
order to adopt such a strategy, we would need to assess the relative
risk associated with each HAP emitted, and determine whether requiring
the control in question would result in overall lower risk. Such an
analysis is not appropriate at this stage in the regulatory process.
For example, the term ``clean coal'' refers to coal that is lower in
sulfur content and not necessarily lower in HAP content. Data gathered
by EPA also indicates that within specific coal types HAP content can
vary significantly. Switching to a low sulfur coal may actually
increase emissions of some HAP. Therefore, it is not appropriate for
EPA to include fuel switching to a low sulfur coal as part of the MACT
standards for boilers that burn hazardous waste.
---------------------------------------------------------------------------
\121\ C. Leatherwood, ERG, to J. Eddinger, OAQPS, EPA,
Memorandum: Development of Fuel Switching Costs and Emission
Reductions for Industrial/Commercial/Institutional Boilers and
Process Heaters National Emission Standards for Hazardous Air
Pollutants, October 2002.
---------------------------------------------------------------------------
We also considered the availability of alternative fuel types.
Natural gas pipelines are not available in all regions of the U.S., and
natural gas is simply not available as a fuel for many solid fuel-fired
boilers. Moreover, even where pipelines provide access to natural gas,
supplies of natural gas may not be adequate. For example, it is common
practice in cities during winter months (or periods of peak demand) to
prioritize natural gas usage for residential areas before industrial
usage. Requiring EPA regulated combustion units to switch to natural
gas would place an even greater strain on natural gas resources.
Consequently, even where pipelines exist, some units would not be able
to run at normal or full capacity during these times if shortages were
to occur. Therefore, under any circumstances, there would be some units
that could not comply with a requirement to switch to natural gas.
In addition, we have significant concern that switching fuels would
be infeasible for sources designed and operated to burn specific fuel
types. Changes in the type of fuel burned by a boiler may require
extensive changes to the fuel handling and feeding system (e.g., a
stoker-fired boiler using coal as primary fuel would need to be
redesigned to handle fuel oil or gaseous fuel as the primary fuel).
Additionally, burners and combustion chamber designs are generally not
capable of handling different fuel types, and generally cannot
accommodate increases or decreases in the fuel volume and shape. Design
changes to allow different fuel use, in some cases, may reduce the
capacity and efficiency of the boiler. Reduced efficiency may result in
less complete combustion and, thus, an increase in organic HAP
emissions. For the reasons discussed above, we conclude that fuel
switching to cleaner solid fuels or to liquid or gaseous fuels is not
an appropriate criteria for identifying the MACT floor level of control
for solid fuel-fired boilers.
A. What Is the Rationale for the Proposed Standards for Dioxin and
Furan?
The proposed standard for dioxin/furan for existing and new sources
is compliance with the proposed carbon monoxide or hydrocarbon (CO/HC)
emission standard and compliance with the proposed destruction and
removal efficiency (DRE) standard. The CO/HC and DRE standards control
emissions of organic HAPs in general, and are discussed in Sections G
and H below. This standard ensures that boilers operate under good
combustion practices as a surrogate for dioxin/furan control. Operating
under good combustion practices minimizes levels of products of
incomplete combustion, including potentially dioxin/furan, and organic
compounds that could be precursors for post-combustion formation of
dioxin/furan. The rationale for the dioxin/furan standard is discussed
below.
1. What Is the Rationale for the MACT Floor for Existing Sources?
The proposed MACT floor control for existing sources is compliance
with the proposed CO/HC emission standard and compliance with the
proposed DRE standard.
Solid fuel-fired boilers that burn hazardous waste cofire the
hazardous waste with coal at firing rates of 6-33% of total heat input.
We have dioxin/furan emission data for one source, and those emissions
are 0.07 ng TEQ/dscm.
Although dioxin/furan can be formed post-combustion in an
electrostatic precipitator or baghouse that is operated at temperatures
within the range of 400[deg]
to 750[deg]F, the boiler for which we have
dioxin/furan emissions data is equipped with an electrostatic
precipitator that operated at 500[deg]F during the emissions test.
Although this is well within the optimum temperature range for
formation of dioxin/furan, dioxin/furan emissions were low. In
addition, this boiler fed chlorine at levels four times greater than
any other solid fuel boiler.\122\ We also have emissions data from 16
nonhazardous waste coal-fired boilers equipped with electrostatic
precipitators and baghouses operated at temperatures up to 480[deg]F,
all of which have dioxin/furan emissions below 0.3 ng TEQ/dscm.\123\ We
conclude from these data and the information discussed below that rapid
quench of post-combustion gas temperatures to below 400[deg]F--the
control technique that is the basis for the MACT standards for
hazardous waste burning incinerators, and cement and lightweight
aggregate kilns--is not the dominant dioxin/furan control mechanism for
coal-fired boilers.
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\122\ Uncontrolled hydrogen chloride in combustion gas was
approximately 700 ppmv.
\123\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 2.
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We believe that sulfur contributed by the coal fuel is a dominant
control mechanism by inhibiting formation of dioxin/furan. Coal
generally contributes from 65% to 95% percent of the boiler's heat
input with the remainder provided by hazardous waste fuel. The presence
of sulfur in combustor feedstocks has been shown to dramatically
inhibit the catalytic formation of dioxin/furan in downstream
temperature zones from 400[deg]F to 750[deg]F. High sulfur coals tend
to inhibit dioxin/furan formation better than low sulfur coals. Id.
Adsorption of any dioxin/furan that may be formed on coal fly ash,
and subsequent capture in the electrostatic precipitator or baghouse,
also may contribute to the low dioxin/furan emissions despite some
boilers operating at relatively high back-end gas temperatures. This
effect is similar to that of using activated carbon injection to
control dioxin/furan emissions. Adsorption of dioxin/furan on fly ash
is related to the carbon content of the fly ash, and, thus, the type of
coal burned. Id.
Operating under good combustion conditions to minimize emissions of
organic compounds such as polychlorinated biphenols, benzene, and
phenol that can be precursors to dioxin/furan formation is an important
requisite to control dioxin/furan emissions. Although sulfur-induced
inhibition may be the dominant mechanism to control dioxin/furan
[[Page 21275]]
emissions from coal-fired boilers, minimizing dioxin/furan precursors
by operating under good combustion practices certainly plays a part in
controlling dioxin/furan emissions.
We propose to use the CO/HC and DRE standards as surrogates to
ensure that boilers operate under good combustion conditions because
quantified levels of control provided by sulfur in the coal and
adsorption onto collected fly ash may not be replicable by the best
performing sources nor duplicable by other sources. Although coal
sulfur content may be a dominant factor affecting dioxin/furan
emissions, we do not know what minimum level of sulfur provides
significant control. Moreover, sulfur in coal causes emissions of
sulfur oxides, a major criteria pollutant, and particulate sulfates.
Similarly, we cannot quantify a minimum carbon content of coal that
would form carbonaceous fly ash with superior dioxin/furan adsorptive
properties. In addition, restricting coal types that may be burned
based on carbon content may have an adverse impact on energy production
at sources burning hazardous waste as fuel. (These considerations raise
the question of whether boilers operating under these conditions would
still be ``best'' performers when these adverse impacts are taken into
account.) For these reasons, and because we have emissions data from
only one source, we cannot establish a numerical dioxin/furan emission
standard.
Operating under good combustion practices is floor control because
all hazardous waste burning boilers are required by existing RCRA
regulations to operate under good combustion conditions to minimize
emissions of toxic organic compounds. See Sec. 266.104 requiring
compliance with DRE and CO/HC emission standards.\124\ We also find, as
required by CAA section 112(h)(1), that these proposed standards are
consistent with section 112(d)'s objective of reducing emissions of
these HAPs to the extent achievable.
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\124\ Section 266.104 requires compliance with a CO limit of 100
ppmv or a HC limit of 20 ppmv, while we are proposing today a CO
limit of 100 ppmv or a HC limit of 10 ppmv (see Section X.H in the
text). Although today's proposed HC limit is more stringent than the
current limit for boilers, all solid fuel boilers chose to comply
with the 100 ppmv CO limit. Moreover, for those liquid-fuel fired
boilers that chose to comply with the 20 ppmv HC limit, their HC
emissions are below 10 ppmv.
---------------------------------------------------------------------------
We request comment on an alternative floor that would be
established as the highest dioxin/furan emission level in our data
base. Because we have dioxin/furan emission data from only one coal-
fired boiler that burns hazardous waste, we would combine that data
point with emissions data from coal-fired boilers that do not burn
hazardous waste since the factors that affect dioxin/furan emissions
from these boilers are not significantly influenced by hazardous waste.
These additional data would better represent the range of emissions
from coal-fired boilers. Under this approach, the dioxin/furan floor
would be an emission level of 0.30 ng TEQ/dscm. We would also use this
approach to establish the same floor for new sources.
Finally, we note that we propose to require a one-time dioxin/furan
emission test for sources that would not be subject to a numerical
dioxin/furan emission standard, such as solid fuel-fired boilers. As
discussed in Part Two, Section XIV.B below, the testing would assist in
developing both section 112(d)(6) standards and section 112(f) residual
risk standards.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
As discussed above, we propose to use the CO/HC and DRE standards
as surrogates to ensure good combustion conditions, and thus, control
of dioxin/furan emissions. We are not proposing beyond-the-floor
standards for CO/HC and DRE, as discussion in Sections G and H below.
We investigated use of activated carbon injection or, for sources
equipped with baghouses, catalytically impregnated fabric felt/membrane
filter materials to achieve a beyond-the-floor standard of 0.10 ng TEQ/
dscm.\125\ To estimate the cost-effectiveness of these beyond-the-floor
control techniques, we imputed dioxin/furan emissions levels for the
six sources for which we don't have measured emissions data. To impute
the missing emissions levels, we used the emissions data from the
hazardous waste burning boiler as well as the emissions data from
nonhazardous waste coal-fired boilers. It may be appropriate to meld
these emissions data because hazardous waste burning should not affect
dioxin/furan emissions from coal-fired boilers. In fact, the
nonhazardous waste coal-fired boilers had somewhat higher emissions
than the hazardous waste coal-fired boiler. (The emissions from the
nonhazardous waste coal-fired boilers may simply represent the range of
emissions that could be expected from hazardous waste coal-fired
boilers, as well, given that we have emissions data from only one
hazardous waste boiler.)
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\125\ We considered a beyond-the-floor standard of 0.20 ng TEQ/
dscm but determined that it may not result in emissions reductions
because the majority of sources (the hazardous waste coal-fired
boiler and the nonhazardous waste coal-fired boilers) appear to emit
dioxin/furan at levels below 0.20 ng TEQ/dscm.
---------------------------------------------------------------------------
The national incremental annualized compliance cost for solid fuel-
fired boilers to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $3.4 million and would
provide an incremental reduction in dioxin/furan emissions beyond the
MACT floor controls of 0.26 grams TEQ tons per year. We also evaluated
the nonair quality health and environmental impacts and energy effects
between activated carbon injection and controls likely to be used to
meet the floor level. We estimate that this beyond-the-floor option
would increase the amount of hazardous waste \126\ generated by 3,300
tons per year and would also require sources to use an additional 1.2
million kW-hours per year. Based on these impacts and costs of
approximately $13 million per additional grams of dioxin/furan removed,
we are not proposing a beyond-the-floor standard based on activated
carbon injection.
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\126\ To estimate the cost of a beyond-the-floor standard
conservatively, we assumed the solid waste generated would be
subject to regulation as hazardous waste. These costs are likely
over-estimated, however, because these residues are not likely to
fail the criteria for retaining the Bevill exclusion under 40 CFR
266.112.
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For these reasons, we propose a floor standard for dioxin/furan for
existing sources of compliance with the proposed CO/HC emission
standard and compliance with the proposed DRE standard.\127\
---------------------------------------------------------------------------
\127\ We note that we propose to require solid fuel-fired
boilers (and liquid fuel-fired boilers that are not subject to a
numerical dioxin/furan standard) to conduct a one-time dioxin/furan
emission test to provide data to assist in developing both section
112(d)(6) standards and section 112(f) residual risk standards. See
discussion in Section XIV.B of the preamble.
---------------------------------------------------------------------------
3. What Is the Rationale for the MACT Floor for New Sources?
As discussed above, we propose to use the CO/HC and DRE standards
as surrogates to ensure good combustion conditions, and thus, control
of dioxin/furan emissions. Because we are proposing the same DRE and
CO/HC standards for existing sources and new sources as discussion in
Sections G and H below, we are proposing the same dioxin/furan floor
for new and existing sources.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We are not proposing beyond-the-floor standards for CO/HC for
dioxin/furan for new solid fuel-fired boilers because we are not
proposing beyond-the-floor standards for CO/HC and DRE
[[Page 21276]]
for new sources. See discussion in Sections G and H below.
In addition, we evaluated activated carbon injection or, for
sources equipped with baghouses, use of catalytically impregnated
fabric felt/membrane filter materials as beyond-the-floor control for
further reduction of dioxin/furan emissions to achieve a beyond-the-
floor level of 0.15 ng TEQ/dscm. The incremental annualized compliance
cost for a new solid fuel-fired boiler with average gas flowrate to
meet this beyond-the-floor level, rather than comply with the floor
level, would be approximately $0.28 million and would provide an
incremental reduction in dioxin/furan emissions of approximately 0.21
grams TEQ per year, for a cost-effectiveness of $1.3 million per gram
of dioxin/furan removed. We estimate that this beyond-the-floor option
would increase the amount of hazardous waste (or solid waste if the
source retains the Bevill exclusion under 40 CFR 266.112) generated for
a new solid fuel-fired boiler with average gas flowrate by 270 tons per
year and would require a source to use an additional 0.1 million kW-
hours per year beyond the requirements to achieve the floor level.
After considering these impacts and a cost of $1.3 million per gram of
dioxin/furan removed, we conclude that a beyond-the-floor standard
based on activated carbon injection or catalytically impregnated fabric
felt/membrane filter is not warranted for new sources. Consequently, we
propose a floor standard for dioxin/furan for new sources: Compliance
with the proposed CO/HC and DRE emissions standards.
B. What Is the Rationale for the Proposed Standards for Mercury?
The proposed standard for mercury for solid fuel-fired boilers is
10 [mu]g/dscm for both existing sources and new sources.\128\
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\128\ As information, EPA proposed MACT standards for mercury
for solid fuel-fired industrial, commercial, and institutional
boilers that do not burn hazardous waste of 5.3 [mu]g/dscm for
existing sources and 3.4 [mu]g/dscm for new sources. See 68 FR 1660
(Jan. 13, 2003). These standards are based on use of fabric filters
to control mercury emissions.
---------------------------------------------------------------------------
1. What Is the Rationale for the MACT Floor for Existing Sources?
The MACT floor for existing sources is 10 [mu]g/dscm based on
adsorption of mercury onto coal fly ash and removal of fly ash by the
electrostatic precipitator or baghouse.
All solid fuel-fired boilers are equipped with electrostatic
precipitators or baghouses. We have compliance test emissions data for
three sources equipped with electrostatic precipitators which document
maximum mercury emissions ranging from 3 ug/dscm to 11 [mu]g/dscm and
system removal efficiencies of 83% to 96%. These three sources
represent seven of the 12 solid fuel-fired boilers.\129\ The Agency has
also determined that coal-fired utility boilers can achieve significant
control of mercury by adsorption on fly ash and particulate matter
control.\130\
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\129\ Owners and operators have used the emissions data from the
three boilers as ``data in lieu of testing'' emissions from other,
identical boilers at the same facility. One of the three boilers as
two such sister identical boilers, and the other two boilers each
have a sister identical boiler. Thus, emissions from these three
boilers represent emissions from seven of the 12 solid fuel-fired
boilers.
\130\ Memo from Frank Princiotta, USEPA, to John Seitz, USEPA,
entitled ``Control of Mercury Emissions from Coal-fired Utility
Boilers,'' dated October 25, 2000.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated the compliance test
emissions data using the SRE/Feed Approach. The calculated floor is 10
[mu]g/dscm, which considers emissions variability. This is an emission
level that the average of the best performing sources could be expected
to achieve in 99 of 100 future tests when operating under operating
conditions identical to the compliance test conditions during which the
emissions data were obtained. We estimate that this emission level is
being achieved by 67% of sources and would provide a reduction in
mercury emissions of 0.015 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of mercury: (1) Activated carbon injection; and (2) control of mercury
in the hazardous waste feed. For reasons discussed below, we are not
proposing a beyond-the-floor standard for mercury.
a. Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. Activated carbon has been demonstrated for controlling
mercury from waste combustion systems and has achieved efficiencies
ranging from 80% to greater than 90% depending on factors such as:
Activated carbon type/impregnation; injection rate; mercury speciation
in the flue gas; and flue gas temperature. We made a conservative
assumption that the use of activated carbon will provide 70% mercury
control for coal-fired boilers given the low mercury levels at the
floor. Applying this activated carbon removal efficiency to the mercury
floor level of 10 [mu]g/dscm would provide a beyond-the-floor level of
3.0 [mu]g/dscm.
The national incremental annualized compliance cost for solid fuel
boilers to meet this beyond-the-floor level rather than comply with the
floor controls would be approximately $1.1 million and would provide an
incremental reduction in mercury emissions beyond the MACT floor
controls of 0.03 tons per year. We evaluated nonair quality health and
environmental impacts and energy effects and estimate that this beyond-
the-floor option would increase the amount of hazardous waste (or solid
waste if the source retains the Bevill exclusion under 40 CFR 266.112)
generated by 1,000 tons per year and would require sources to use an
additional 0.35 million kW-hours per year beyond the requirements to
achieve the floor level. Based on these factors and costs of
approximately $35 million per additional ton of mercury removed, we are
not proposing a beyond-the-floor standard based on activated carbon
injection.
b. Feed Control of Mercury in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 8 [mu]g/dscm, which represents a
20% reduction from the floor level. The national incremental annualized
compliance cost for solid fuel boilers to meet this beyond-the-floor
level rather than comply with the floor controls would be approximately
$0.11 million and would provide an incremental reduction in mercury
emissions beyond the MACT floor controls of 0.005 tons per year. Nonair
quality health and environmental impacts and energy effects are not
significant factors for feedrate control.
We are not proposing a beyond-the-floor standard based on feed
control of mercury in the hazardous waste because it would not be cost-
effective at approximately $23 million per additional ton of mercury
removed. Consequently, we propose a floor standard for mercury for
existing sources of 10 [mu]g/dscm.
3. What Is the Rationale for MACT Floor for New Sources?
MACT floor for new sources would be 10 [mu]g/dscm, the same as the
floor for existing sources. This is an emission level that the single
best performing source identified by the SRE/Feed Approach could be
expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We identified the same two potential beyond-the-floor techniques
for control
[[Page 21277]]
of mercury: (1) Use of activated carbon injection; and (2) control of
mercury in the hazardous waste feed.
We evaluated use of carbon injection for new sources to achieve a
beyond-the-floor emission level of 5.0 [mu]g/dscm. The incremental
annualized compliance cost for a new solid fuel boiler with average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $0.28 million and would provide
an incremental reduction in mercury emissions of approximately 0.008
tons per year, for a cost-effectiveness of $37 million per ton of
mercury removed. We estimate that this beyond-the-floor option would
increase the amount of hazardous waste (or solid waste if the source
retains the Bevill exclusion under 40 CFR 266.112) generated for a new
solid fuel-fired boiler with average gas flowrate by 270 tons per year
and would require a source to use an additional 0.1 million kW-hours
per year beyond the requirements to achieve the floor level. After
considering these impacts and, primarily, cost-effectiveness, we are
not proposing a beyond-the-floor standard based on activated carbon
injection for new sources. Consequently, we propose a floor standard
for mercury of 10 [mu]g/dscm for new sources.
C. What Is the Rationale for the Proposed Standards for Particulate
Matter?
The proposed standards for particulate matter for solid fuel-fired
boilers are 69 mg/dscm (0.030 gr/dscf) for existing sources and 34 mg/
dscm (0.015 gr/dscf) for new sources.\131\ The particulate matter
standard serves as a surrogate for nonmercury HAP metals in emissions
from the coal burned in the boiler, and for nonenumerated HAP metal
emissions attributable to the hazardous waste fuel burned in the
boiler.
---------------------------------------------------------------------------
\131\ As information, EPA proposed MACT standards for
particulate matter for solid fuel-fired industrial, commercial, and
institutional boilers that do not burn hazardous waste of 0.035 gr/
dscf for existing sources and 0.013 gr/dscf for new sources. See 68
FR 1660 (Jan. 13, 2003). These standards are based on control of
particulate matter emissions using a fabric filter.
---------------------------------------------------------------------------
1. What Is the Rationale for the MACT Floor for Existing Sources?
All solid fuel-fired boilers are equipped with electrostatic
precipitators or baghouses. We have compliance test emissions data for
seven boilers. Emissions from these seven boilers represent emissions
from all 12 solid fuel-fired boilers.\132\ Particulate emissions range
from 0.021 gr/dscf to 0.037 gr/dscf.\133\
---------------------------------------------------------------------------
\132\ Owners and operators have determined that emissions from
these seven boilers represent emissions from five other identical,
sister boilers. Owners and operators have used the emissions from
these seven boilers as ``data in lieu of testing'' emissions from
the other five identical boilers.
\133\ Although particulate matter emissions are predominantly
attributable to coal ash rather than ash from hazardous waste fuel,
we did not combine emissions data for coal-fired boilers that do not
burn hazardous waste with the data for boilers that burn hazardous
waste because we have particulate emissions data for all boilers
that burn hazardous waste.
---------------------------------------------------------------------------
To identify the floor level, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
air pollution control device approach. See discussion in Part Two,
Section VI.A.2.a. The calculated floor is 140 mg/dscm (0.063 gr/dscf),
which considers emissions variability. This is an emission level that
the average of the best performing sources could be expected to achieve
in 99 of 100 future tests when operating under conditions identical to
the compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 75%
of sources. Compliance with the floor level would reduce particulate
matter emissions by 33 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated improved design, operation, and maintenance of the
existing electrostatic precipitators (e.g., humidification to improve
gas conditioning) and baghouses (e.g., improved bags) for these boilers
to achieve a beyond-the-floor emission level of 69 mg/dscm (0.030 gr/
dscf). We also evaluated a more stringent standard based on adding a
polishing fabric filter to achieve a beyond-the-floor emission level of
0.015 gr/dscf. The national incremental annualized compliance cost for
solid fuel boilers to meet a beyond-the-floor level of 69 mg/dscm
rather than comply with the floor controls would be approximately $1.3
million and would provide an incremental reduction in particulate
matter emissions beyond the MACT floor controls of 400 tons per year
and an incremental reduction in metal HAP of 6.8 tons per year. We
evaluated nonair quality health and environmental impacts and energy
effects and estimate that this beyond-the-floor option would increase
the amount of hazardous waste (or solid waste if the source retains its
Bevill exclusion under 40 CFR 266.112) generated by 380 tons per year
and would require sources to use an additional 3.3 million kW-hours per
year and to use an additional 160 million gallons of water beyond the
requirements to achieve the floor level.
Notwithstanding these nonair quality health and environmental
impacts and energy effects, a beyond-the-floor standard of 69 mg/dscm
(0.030 gr/dscf) based on improved particulate matter control is
warranted because it is cost-effective at a cost of approximately
$3,200 per additional ton of particulate matter removed and a cost of
approximately $190,000 per additional ton of metal HAP removed.\134\ In
addition, the average incremental annualized cost would be only
$120,000 per facility. We also note that, although section 112(d) only
authorizes control of HAPs, and particulate matter is not itself a HAP
but a surrogate for HAP metals, Congress expected the MACT program to
result in significant emissions reductions of criteria air pollutants
(of which particulate matter is one), and viewed this as an important
benefit of the MACT (and residual risk) provisions. See 5 Legislative
History at 8512 (Senate Committee Report). Finally, we note that this
beyond-the-floor standard of 0.030 gr/dscf would be comparable to the
floor-based standard the Agency recently promulgated for solid fuel-
fired boilers that do not burn hazardous waste: 0.07 lb/MM Btu
(approximately 0.034 gr/dscf). See NESHAP for Industrial/Commercial/
Institutional Boilers and Process Heaters, signed Feb. 26, 2004.
Because hazardous waste does not contribute substantially to
particulate matter emissions from coal-fired boilers, MACT standards
for solid fuel boilers should be similar irrespective of whether they
burn hazardous waste.
---------------------------------------------------------------------------
\134\ Note that we are not proposing beyond-the-floor
particulate matter standards for incinerators, cement kilns,
lightweight aggregate kilns, and liquid fuel-fired boilers because
those standards would have a cost-effectiveness of $12,000 to
$80,000 per ton of particulate matter removed, substantially higher
than the $3,200 per ton cost-effectiveness of a beyond-the-floor
standard for solid fuel-fired boilers.
---------------------------------------------------------------------------
A 34 mg/dscm beyond-the-floor standard for existing sources based
on use of a polishing fabric filter would remove an additional 570 tons
per year of particulate matter beyond the floor level at a cost-
effectiveness of $9,800 per ton removed. We conclude that this standard
would not be as cost-effective as a 69 mg/dscm standard and would
result in greater nonair quality health and environmental impacts and
energy effects. For these reasons, we propose a beyond-the-floor
particulate matter standard of 0.030 gr/dscf (69 mg/dscm) for existing
sources. We specifically request comment on whether this beyond-the-
floor standard is warranted.
[[Page 21278]]
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be 90 mg/dscm (0.040 gr/dscf),
considering emissions variability. This is an emission level that the
single best performing source identified by the APCD Approach (i.e.,
the source using a fabric filter with the lowest emissions) could be
expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated use of a fabric filter to achieve a beyond-the-floor
emission level of 34 mg/dscm (0.015 gr/dscf). The incremental
annualized cost for a new solid fuel-fired boiler with average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $280,000 and would provide an
incremental reduction in particulate emissions of approximately 44 tons
per year, for a cost-effectiveness of $6,400 per ton of particulate
matter removed. We estimate that this beyond-the-floor option would
increase the amount of hazardous waste (or solid waste if the source
retains the Bevill exclusion under 40 CFR 266.112) generated for a new
solid fuel-fired boiler with average gas flowrate by 44 tons per year
and would require a source to use an additional 1.1 million kW-hours
per year beyond the requirements to achieve the floor level.
Notwithstanding these impacts, a standard of 34 mg/dscm (0.015 gr/dscf)
is warranted because it would be cost-effective and it would remove
additional nonenumerated metal HAP. We also note that this beyond-the-
floor standard of 0.015 gr/dscf for new sources would be comparable to
the floor-based standard the Agency recently promulgated for new solid
fuel-fired boilers that do not burn hazardous waste: 0.025 lb/MM Btu
(approximately 0.012 gr/dscf). See NESHAP for Industrial/Commercial/
Institutional Boilers and Process Heaters, signed Feb. 26, 2004.
For these reasons, we propose a beyond-the-floor particulate matter
standard of 34 mg/dscm (0.015 gr/dscf) for new sources. We specifically
request comment on whether this beyond-the-floor standard is warranted.
D. What Is the Rationale for the Proposed Standards for Semivolatile
Metals?
The proposed standard for semivolatile metals (lead and cadmium,
combined) for solid fuel-fired boilers is 170 [mu]g/dscm for both
existing and new sources.\135\
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\135\ As information, EPA proposed to control nonmercury metal
HAP emissions for industrial, commercial, and institutional boilers
that do not burn hazardous waste with a particulate matter emission
standard only. See 68 FR 1660 (Jan. 13, 2003). For hazardous waste
combustors, we propose to control specific, enumerated semivolatile
and low volatile metals with separate emission standards because
hazardous waste can have a wide range of concentrations of these
metals, and, thus, particulate matter may contain a wide range of
metal concentrations. Thus, particulate matter may not be an
effective surrogate for particular metal HAP. Nonetheless, for
practical reasons, we rely on particulate matter to control
nonenumerated metal HAP.
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1. What Is the Rationale for the MACT Floor for Existing Sources?
We have compliance test emissions data for four boilers. Emissions
from these four boilers represent emissions from nine of the 12 solid
fuel-fired boilers.\136\ Semivolatile metal emissions range from 62
[mu]g/dscm to 170 [mu]g/dscm. These emissions are expressed as mass of
semivolatile metals (from all feedstocks) per unit of stack gas.
---------------------------------------------------------------------------
\136\ Owners and operators have determined that emissions from
these four boilers represent emissions from five other identical,
sister boilers. Owners and operators have used the emissions from
these four boilers as ``data in lieu of testing'' emissions from the
other five identical boilers.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 170 [mu]g/dscm, which
considers emissions variability. This is an emission level that the
average of the best performing sources could be expected to achieve in
99 of 100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this floor level is being achieved by 42% of
sources and would reduce semivolatile metals emissions by 0.22 tons per
year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated three beyond-the-floor approaches for semivolatile
metals for existing sources: (1) Improved control of particulate
matter; (2) control of semivolatile metals in the hazardous waste feed;
and (3) a no-cost standard derived from the beyond-the-floor
particulate matter standard. For reasons discussed below, we are not
proposing a beyond-the-floor standard for semivolatile metals.
a. Improved Particulate Matter Control. Controlling particulate
matter also controls emissions of semivolatile metals. Consequently, we
evaluated a beyond-the-floor level of 85 [mu]g/dscm, a 50 percent
reduction in semivolatile metal emissions, that would be achieved by
reducing particulate matter emissions. The national incremental
annualized compliance cost for solid fuel boilers to meet this beyond-
the-floor level rather than comply with the floor controls would be
approximately $0.29 million and would provide an incremental reduction
in semivolatile metals emissions beyond the MACT floor controls of 0.29
tons per year. We evaluated the nonair quality health and environmental
impacts and energy effects of this beyond-the-floor standard and
estimate that the amount of hazardous waste generated would increase by
approximately 133 tons per year, an additional 61 million gallons per
year of water would be used, and an additional 1.3 million kW-hours per
year of electricity would be used. Therefore, based on these factors
and costs of approximately $1 million per additional ton of
semivolatile metals removed, we are not proposing a beyond-the-floor
standard based on improved particulate matter control.
b. Feed Control of Semivolatile Metals in the Hazardous Waste. We
also evaluated a beyond-the-floor level of 140 [mu]g/dscm based on
additional control of semivolatile metals in the hazardous waste feed.
This represents a 20% reduction from the floor level. The national
incremental annualized compliance cost for solid fuel boilers to meet
this beyond-the-floor level rather than comply with the floor controls
would be approximately $36,000 and would provide an incremental
reduction in semivolatile metals emissions beyond the MACT floor
controls of 0.046 tons per year. Although nonair quality health and
environmental impacts and energy effects are not significant factors,
we are not proposing a beyond-the-floor standard based on feed control
of semivolatile metals in the hazardous waste because it is not cost-
effective at approximately $0.78 million per additional ton of
semivolatile metals removed.
c. No-cost Standard Derived from the Beyond-the-Floor Particulate
Matter Standard. The beyond-the-floor standard for particulate matter
would also provide beyond-the-floor control for semivolatile metals if
sources were to comply with the beyond-the-floor particulate matter
standard using improved particulate matter control
[[Page 21279]]
rather than by reducing the feedrate of ash. To identify a beyond-the-
floor emission level for semivolatile metals that would derive from the
beyond-the-floor particulate matter standard, we assumed that emissions
of semivolatile metals would be reduced by the same percentage that
sources would need to reduce particulate matter emissions. We then
developed a revised semivolatile metal emission data base considering
these particulate matter standard-derived reductions and reductions
needed to meet the semivolatile metal floor level. We analyzed these
revised emissions to identify the best performing sources and an
emission level that the average of the best performers could achieve 99
out of 100 future tests. This emission level--82 [mu]g/dscm--is a
beyond-the-floor semivolatile metal standard that can be achieved at no
cost because the costs have been allocated to the particulate matter
beyond-the-floor standard.
We are concerned, however, that sources may choose to comply with
the beyond-the-floor particulate matter standard by controlling the
feedrate of ash in the hazardous waste feed, which may or may not
reduce the feedrate and emissions of metal HAP. If so, it would be
inappropriate to consider the beyond-the-floor standard for
semivolatile metals discussed above as a no-cost standard. We
specifically request comment on whether sources may comply with beyond-
the-floor particulate matter standard by controlling the feedrate of
ash.
For these reasons, we propose a floor standard for semivolatile
metals of 170 [mu]g/dscm for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be 170 [mu]g/dscm, considering
emissions variability. This is the same as the floor for existing
sources. This is an emission level that the single best performing
source identified by the SRE/Feed Approach could be expected to achieve
in 99 of 100 future tests when operating under operating conditions
identical to the compliance test conditions during which the emissions
data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated three beyond-the-floor approaches for semivolatile
metals for new sources: (1) Improved particulate matter controls; (2)
control of semivolatile metals in the hazardous waste feed; and (3) a
no-cost standard derived from the beyond-the-floor particulate matter
standard.
a. Improved Particulate Matter Controls. We evaluated improved
control of particulate matter using a fabric filter as beyond-the-floor
control for further reductions in semivolatile metals emissions. We
evaluated a beyond-the-floor level of 71 [mu]g/dscm. The incremental
annualized compliance cost for a new solid fuel boiler with average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $0.28 million and would provide
an incremental reduction in semivolatile metals emissions of
approximately 0.15 tons per year, for a cost-effectiveness of $1.8
million per ton of semivolatile metals removed. We estimate that this
beyond-the-floor option would increase the amount of hazardous waste
(or solid waste if the source retains the Bevill exclusion under 40 CFR
266.112) generated for a new solid fuel-fired boiler with average gas
flowrate by 44 tons per year and would require the source to use an
additional 1.2 million kW-hours per year beyond the requirements to
achieve the floor level. After considering these impacts and cost-
effectiveness, we conclude that a beyond-the-floor standard for new
sources based on use of a fabric filter to improve control of
particulate matter is not warranted.
b. Feedrate Control. For similar reasons discussed above for
existing sources, we conclude that a beyond-the-floor standard based on
controlling the semivolatile metals in the hazardous waste feed would
not be cost-effective.
c. No-cost Standard Derived from the Beyond-the-Floor Particulate
Matter Standard. As discussed above in the context of existing sources,
the beyond-the-floor standard for particulate matter would also provide
beyond-the-floor control for semivolatile metals if sources were to
comply with the beyond-the-floor particulate matter standard using
improved particulate matter control rather than by reducing the
feedrate of ash. Under this approach, the no-cost beyond-the-floor
standard for semivolatile metals for new sources would be 44 [mu]g/
dscm. As discussed above, however, we are concerned that sources may
choose to comply with the beyond-the-floor particulate matter standard
by controlling the feedrate of ash in the hazardous waste feed, which
may or may not reduce the feedrate and emissions of metal HAP. If so,
it would be inappropriate to consider this beyond-the-floor standard as
a no-cost standard. We specifically request comment on whether sources
may comply with beyond-the-floor particulate matter standard by
controlling the feedrate of ash.
For these reasons, we propose a semivolatile metals standard of 170
[mu]g/dscm for new sources.
E. What Is the Rationale for the Proposed Standards for Low Volatile
Metals?
The proposed standards for low volatile metals (arsenic, beryllium,
and chromium) for solid fuel-fired boilers is 210 [mu]g/dscm for
existing sources and 190 [mu]g/dscm for new sources.
1. What Is the Rationale for the MACT Floor for Existing Sources?
We have compliance test emissions data for four boilers. Emissions
from these four boilers represent emissions from 10 of the 12 solid
fuel-fired boilers.\137\ Low volatile metal emissions range from 41
[mu]g/dscm to 230 [mu]g/dscm. These emissions are expressed as mass of
low volatile metals (from all feedstocks) per unit of stack gas.
---------------------------------------------------------------------------
\137\ Owners and operators have determined that emissions from
these four boilers represent emissions from five other identical,
sister boilers. Owners and operators have used the emissions from
these four boilers as ``data in lieu of testing'' emissions from the
other five identical boilers.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 210 [mu]g/dscm, which
considers emissions variability. This is an emission level that the
average of the best performing sources could be expected to achieve in
99 of 100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 67%
of sources and that it would reduce low volatile metals emissions by
0.45 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated three beyond-the-floor approaches for low volatile
metals for existing sources: (1) Improved control of particulate
matter; (2) control of low volatile metals in the hazardous waste feed;
and (3) a no-cost standard derived from the beyond-the-floor
particulate matter standard. For reasons discussed below, we are not
proposing a beyond-the-floor standard for low volatile metals.
a. Improved Particulate Matter Control. Controlling particulate
matter also controls emissions of low volatile metals. We evaluated a
beyond-the-floor level of 105 [mu]g/dscm. The national incremental
annualized compliance cost for solid fuel boilers to meet this
[[Page 21280]]
beyond-the-floor level rather than comply with the floor controls would
be approximately $0.32 million and would provide an incremental
reduction in low volatile metals emissions beyond the MACT floor
controls of 0.37 tons per year. We evaluated the nonair quality health
and environmental impacts and energy effects of this beyond-the-floor
standard and estimate that the amount of hazardous waste generated
would increase by approximately 83 tons per year, an additional 54
million gallons of water per year would be used, and electricity
consumption would increase by 1.2 million kW-hours per year.
Considering these impacts and a cost of approximately $0.87 million per
additional ton of low volatile metals removed, we are not proposing a
beyond-the-floor standard based on improved particulate matter control.
b. Feed Control of Low Volatile Metals in the Hazardous Waste. We
also evaluated a beyond-the-floor level of 170 [mu]g/dscm, which
represents a 20% reduction from the floor level. The national
incremental annualized compliance cost for solid fuel boilers to meet
this beyond-the-floor level rather than comply with the floor controls
would be approximately $98,000 and would provide an incremental
reduction in low volatile metals emissions beyond the MACT floor
controls of 0.13 tons per year. Although nonair quality health and
environmental impacts and energy effects are not significant factors,
we are not proposing a beyond-the-floor standard based on feedrate
control of low volatile metals in the hazardous waste because it would
not be cost-effective at approximately $0.78 million per additional ton
of low volatile metals removed.
c. No-cost Standard Derived from the Beyond-the-Floor Particulate
Matter Standard. As discussed above in the context of semivolatile
metals, the beyond-the-floor standard for particulate matter would also
provide beyond-the-floor control for low volatile metals if sources
were to comply with the beyond-the-floor particulate matter standard
using improved particulate matter control rather than by reducing the
feedrate of ash. To identify a beyond-the-floor emission level for low
volatile metals that would derive from the beyond-the-floor particulate
matter standard, we assumed that emissions of low volatile metals would
be reduced by the same percentage that sources would need to reduce
particulate matter emissions. We then developed a revised low volatile
metal emission data base considering these particulate matter standard-
derived reductions and reductions needed to meet the low volatile metal
floor level. We analyzed these revised emissions to identify the best
performing sources and an emission level that the average of the best
performers could achieve 99 out of 100 future tests. This emission
level--110 [mu]g/dscm--is a beyond-the-floor low volatile metal
standard that can be achieved at no cost because the costs have been
allocated to the particulate matter beyond-the-floor standard.
We are concerned, however, that sources may choose to comply with
the beyond-the-floor particulate matter standard by controlling the
feedrate of ash in the hazardous waste feed, which may or may not
reduce the feedrate and emissions of metal HAP. If so, it would be
inappropriate to consider the beyond-the-floor standard for low
volatile metals discussed above as a no-cost standard. We specifically
request comment on whether sources may comply with beyond-the-floor
particulate matter standard by controlling the feedrate of ash.
For these reasons, we propose a floor standard for low volatile
metals of 210 [mu]g/dscm for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for low volatile metals for new sources would be 190
[mu]g/dscm, considering emissions variability. This is an emission
level that the single best performing source identified by the SRE/Feed
Approach could be expected to achieve in 99 of 100 future tests when
operating under operating conditions identical to the compliance test
conditions during which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated three beyond-the-floor approaches for low volatile
metals for new sources: (1) Improved particulate matter control; (2)
control of low volatile metals in the hazardous waste feed; and (3) a
no-cost standard derived from the beyond-the-floor particulate matter
standard.
a. Improved Particulate Matter Control. We evaluated improved
control of particulate matter using a fabric filter to achieve an
emission level of 79 [mu]g/dscm as beyond-the-floor control for low
volatile metals emissions. The incremental annualized compliance cost
for a new solid fuel boiler to meet this beyond-the-floor level, rather
than comply with the floor level, would be approximately $0.28 million
and would provide an incremental reduction in low volatile metals
emissions of approximately 0.17 tons per year, for a cost-effectiveness
of $1.7 million per ton of low volatile metals removed. We estimate
that this beyond-the-floor option would increase the amount of
hazardous waste (or solid waste if the source retains the Bevill
exclusion under 40 CFR 266.112) generated for a new solid fuel-fired
boiler with average gas flowrate by 44 tons per year and would require
the source to use an additional 1.2 million kW-hours per year beyond
the requirements to achieve the floor level. After considering these
impacts and cost-effectiveness, we conclude that a beyond-the-floor
standard based on improved particulate matter control using a fabric
filter for new sources is not warranted.
b. Feedrate Control. For similar reasons discussed above for
existing sources, we conclude that a beyond-the-floor standard based on
controlling the low volatile metals in the hazardous waste feed would
not be cost-effective.
c. No-cost Standard Derived from the Beyond-the-Floor Particulate
Matter Standard. As discussed above in the context of existing sources,
the beyond-the-floor standard for particulate matter would also provide
beyond-the-floor control for low volatile metals if sources were to
comply with the beyond-the-floor particulate matter standard using
improved particulate matter control rather than by reducing the
feedrate of ash. Under this approach, the no-cost beyond-the-floor
standard for low volatile metals for new sources would be 34 [mu]g/
dscm. As discussed above, however, we are concerned that sources may
choose to comply with the beyond-the-floor particulate matter standard
by controlling the feedrate of ash in the hazardous waste feed, which
may or may not reduce the feedrate and emissions of metal HAP. If so,
it would be inappropriate to consider this beyond-the-floor standard as
a no-cost standard. We specifically request comment on whether sources
may comply with beyond-the-floor particulate matter standard by
controlling the feedrate of ash.
For these reasons, we propose a low volatile metals standard of 190
[mu]g/dscm for new sources.
F. What Is the Rationale for the Proposed Standards for Total Chlorine?
The proposed standards for hydrogen chloride and chlorine gas
(i.e., total chlorine, reported as a hydrogen chloride equivalents) for
solid fuel-fired boilers are 440 ppmv for existing sources and 73 ppmv
for new sources.\138\
---------------------------------------------------------------------------
\138\ As information, EPA proposed MACT standards for hydrogen
chloride for solid fuel-fired industrial, commercial, and
institutional boilers that do not burn hazardous waste of 68 ppmv
for existing sources and 15 ppmv for new sources. See 68 FR 1660
(Jan. 13, 2003). These standards are based on use of wet scrubbers
to control hydrogen chloride.
---------------------------------------------------------------------------
[[Page 21281]]
1. What Is the Rationale for the MACT Floor for Existing Sources?
Solid fuel-fired boilers that burn hazardous waste are equipped
with electrostatic precipitators or baghouses and do not have back-end
controls for total chlorine. Total chlorine emissions are controlled by
controlling the feedrate of chlorine in the hazardous waste feed. We
have compliance test emissions data for five boilers. Emissions from
these five boilers represent emissions from 10 of the 12 solid fuel-
fired boilers.\139\ Total chlorine emissions range from 60 ppmv to 700
ppmv.
---------------------------------------------------------------------------
\139\ Owners and operators have determined that emissions from
these five boilers represent emissions from five other identical,
sister boilers. Owners and operators have used the emissions from
these five boilers as ``data in lieu of testing'' emissions from the
other five identical boilers.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated the compliance test
emissions data associated with the most recent test campaign using the
SRE/Feed Approach. The calculated floor is 440 ppmv, which considers
emissions variability. This is an emission level that the best
performing feed control sources could be expected to achieve in 99 of
100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this emission level is being achieved by 83%
of sources and that it would reduce total chlorine emissions by 420
tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated dry scrubbing to achieve a beyond-the-floor emission
level of 110 ppmv for total chlorine for existing sources, assuming
conservatively a 75% removal efficiency. The national annualized
incremental compliance cost for solid fuel-fired boilers to comply with
this beyond-the-floor level rather than the floor level would be $3.7
million, and emissions of total chlorine would be reduced by an
additional 790 tons per year, for a cost-effectiveness of $4,700 per
ton of total chlorine removed. We evaluated the nonair quality health
and environmental impacts and energy effects of this beyond-the-floor
level and estimate that the amount of hazardous waste generated would
increase by 18,000 tons per year, an additional 27 million gallons of
water per year would be used, and electricity consumption would
increase by 0.11 million kW-hours per year.
We note that a cost of $4,700 per additional ton of total chlorine
removed is in the ``grey area'' between a cost the Agency has concluded
is cost-effective and a cost the Agency has concluded is not cost-
effective under other MACT rules. EPA concluded that a cost of $1,100
per ton of total chlorine removed for hazardous waste burning
lightweight aggregate kilns was cost-effective in the 1999 MACT final
rule. See 68 FR at 52900. EPA concluded, however, that a cost of
$45,000 per ton of hydrogen chloride removed was not cost-effective for
industrial boilers. See 68 FR at 1677.
Although a beyond-the-floor standard of 110 ppmv for solid fuel
boilers under today's rule would provide health benefits from
collateral reductions in SO2 emissions,\140\ we are
concerned that a cost of $4,700 per additional ton of total chlorine
removed is not warranted. Therefore, after considering cost-
effectiveness and nonair quality health and environmental impacts and
energy effects, we are not proposing a beyond-the-floor standard based
on dry scrubbing. We specifically request comment on whether a beyond-
the-floor standard is warranted.
---------------------------------------------------------------------------
\140\ See U.S. EPA, ``Addendum to the Assessment of the
Potential Costs, Benefits, and Other Impacts of the Hazardous Waste
Combustion MACT Replacement Standards--Proposed Rule,'' March 2004.
---------------------------------------------------------------------------
We also evaluated use of feedrate control of chlorine in hazardous
waste to achieve a beyond-the-floor level of 350 ppmv, which represents
a 20% reduction from the floor level. The national annualized
incremental compliance cost for solid fuel-fired boilers to comply with
this beyond-the-floor level rather than the floor level would be $0.08
million, and emissions of total chlorine would be reduced by an
additional 40 tons per year, for a cost-effectiveness of $2,000 per ton
of total chlorine removed. Although nonair quality health and
environmental impacts and energy effects are not significant factors
for feedrate control, we are not proposing a beyond-the-floor standard
based on hazardous waste feedrate control because we are concerned
about the practicability of achieving these emissions reductions, and
our estimate of the associated cost, using feedrate control. We
specifically request comment on use of feedrate control of chlorine in
hazardous waste as a beyond-the-floor control technique, the emission
reductions that could be achieved, and the costs of achieving those
reductions.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be 73 ppmv. This is an emission
level that the single best performing source identified by the
Emissions Approach (i.e., the source with the lowest emissions) could
be expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated dry lime scrubbing to achieve a beyond-the-floor
emission level of 37 ppmv for total chlorine for new sources, assuming
conservatively a 50% removal efficiency.\141\ The incremental
annualized compliance cost for a new solid fuel boiler with average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $610,000 and would provide an
incremental reduction in total chlorine emissions of approximately 42
tons per year. Although nonair quality health and environmental impacts
and energy effects are not significant factors, we conclude that a
beyond-the-floor standard of 37 ppmv is not warranted because it would
not be cost-effective at approximately $14,000 per additional ton of
total chlorine removed.
---------------------------------------------------------------------------
\141\ Although we assumed dry scrubbing can readily achieve 75%
removal of total chlorine for beyond-the-floor control for existing
sources, assuming 50% removal for beyond-the-floor control for new
sources is appropriate. This is because the floor for new sources--
73 ppmv--is substantially lower than the floor for existing
sources--440 ppmv--and dry scrubbing is less efficient at lower
uncontrolled emission levels.
---------------------------------------------------------------------------
For these reasons, we propose a floor standard for total chlorine
of 73 ppmv for new sources.
G. What Is the Rationale for the Proposed Standards for Carbon Monoxide
or Hydrocarbons?
To control emissions of organic HAP, existing and new sources would
be required to comply with either a carbon monoxide standard of 100
ppmv or a hydrocarbon standard of 10 ppmv.\142\
---------------------------------------------------------------------------
\142\ As information, EPA proposed MACT standards for carbon
monoxide for new solid fuel-fired industrial, commercial, and
institutional boilers that do not burn hazardous waste of 400 ppmv
corrected to 3% oxygen. See 68 FR 1660 (Jan. 13, 2003).
---------------------------------------------------------------------------
1. What Is the Rationale for the MACT Floor for Existing Sources?
Solid fuel-fired boilers that burn hazardous waste are currently
subject to RCRA standards that require
[[Page 21282]]
compliance with either a carbon monoxide standard of 100 ppmv, or a
hydrocarbon standard of 20 ppmv. Compliance is based on an hourly
rolling average as measured with a CEMS. See Sec. 266.104(a). We are
proposing today floor standards of 100 ppmv for carbon monoxide or 10
ppmv for hydrocarbons.
Floor control for existing sources is operating under good
combustion practices including: (1) Providing adequate excess air with
use of oxygen CEMS and feedback air input control; (2) providing
adequate fuel/air mixing; (3) homogenizing hazardous waste fuels (such
as by blending or size reduction) to control combustion upsets due to
very high or very low volatile content wastes; (4) regulating waste and
air feedrates to ensure proper combustion temperature and residence
time; (5) characterizing waste prior to burning for combustion-related
composition (including parameters such as heating value, volatile
content, liquid waste viscosity, etc.); (6) ensuring the source is
operated by qualified, experienced operators; and (7) periodic
inspection and maintenance of combustion system components such as
burners, fuel and air supply lines, injection nozzles, etc. Given that
there are many interdependent parameters that affect combustion
efficiency and thus carbon monoxide and hydrocarbon emissions, we are
not able to quantify ``good combustion practices.''
Ten of 12 solid fuel-fired boilers are currently complying with the
RCRA carbon monoxide limit of 100 ppmv on an hourly rolling average.
The remaining two boilers are complying with the RCRA hydrocarbon limit
of 20 ppmv on an hourly rolling average. Those boilers have hydrocarbon
levels below 5 ppmv, however, indicative of operating under good
combustion practices.
We propose a floor level for carbon monoxide level of 100 ppmv
because it is a currently enforceable Federal standard. Although the
best performing sources are achieving carbon monoxide levels below 100
ppmv, it is not appropriate to establish a lower floor level because
carbon monoxide is a surrogate for nondioxin/furan organic HAP. As
such, lowering the carbon monoxide floor may not significantly reduce
organic HAP emissions. In addition, it would be inappropriate to apply
a MACT methodology to the carbon monoxide emissions from the best
performing sources because those sources may not be able to replicate
their emission levels. This is because there are myriad factors that
affect combustion efficiency and, subsequently, carbon monoxide
emissions. Extremely low carbon monoxide emissions cannot be assured by
controlling only one or two operating parameters We note also that we
used this rationale to establish a carbon monoxide standard of 100 ppmv
for Phase I sources in the September 1999 Final Rule.
We propose a floor level for hydrocarbons of 10 ppmv even though
the currently enforceable standard is 20 ppmv because: (1) The two
sources that comply with the RCRA hydrocarbon standard can readily
achieve 10 ppmv; and (2) reducing hydrocarbon emissions within the
range of 20 ppmv to 10 ppmv should reduce emissions of nondioxin/furan
organic HAP. We do not apply a prescriptive MACT methodology to
establish a hydrocarbon floor below 10 ppmv, however, because we have
data from only two sources. In addition, we note that the hydrocarbon
emission standard for Phase I sources established in the September 1999
Final Rule is 10 ppmv also.
There would be no incremental emission reductions associated with
these floors because all sources are currently achieving the floor
levels.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered beyond-the-floor levels for carbon monoxide and
hydrocarbons based on use of better combustion practices but conclude
that they may not be replicable by the best performing sources nor
duplicable by other sources given that we cannot quantify good
combustion practices. Moreover, we cannot ensure that carbon monoxide
or hydrocarbon levels lower than the floors would significantly reduce
emissions of nondioxin/furan organic HAP. This is because the portion
of hydrocarbons that is comprised of nondioxin/furan organic HAP is
likely to become lower as combustion efficiency improves and
hydrocarbon levels decrease. Thus, at beyond-the-floor hydrocarbon
levels, we would expect a larger portion of residual hydrocarbons to be
compounds that are not organic HAP.
Nonair quality health and environmental impacts and energy
requirements are not significant factors for use of better combustion
practices as beyond-the-floor control.
For these reasons, we conclude that beyond-the-floor standards for
carbon monoxide and hydrocarbons are not warranted for existing
sources.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be the same as the floor for
existing sources--100 ppmv for carbon monoxide and 10 ppmv for
hydrocarbons--and based on the same rationale.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
As discussed in the context of beyond-the-floor considerations for
existing sources, we considered beyond-the-floor standards for carbon
monoxide and hydrocarbons for new sources based on use of better
combustion practices. But, we conclude that beyond the floor standards
may not be replicable by the best performing sources nor duplicable by
other sources given that we cannot quantify good combustion practices.
Moreover, we cannot ensure that carbon monoxide or hydrocarbon levels
lower than the floors would significantly reduce emissions of
nondioxin/furan organic HAP.
Nonair quality health and environmental impacts and energy
requirements are not significant factors for use of better combustion
practices as beyond-the-floor control.
For these reasons, we conclude that beyond-the-floor standards for
carbon monoxide and hydrocarbons are not warranted for new sources.
H. What Is the Rationale for the Proposed Standard for Destruction and
Removal Efficiency?
To control emissions of organic HAP, existing and new sources would
be required to comply with a destruction and removal efficiency (DRE)
of 99.99% for organic HAP. For sources burning hazardous wastes F020,
F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999%
for organic HAP.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Solid fuel-fired boilers that burn hazardous waste are currently
subject to RCRA DRE standards that require 99.99% destruction of
designated principal organic hazardous constituents (POHCs). For
sources that burn hazardous wastes F020, F021, F022, F023, F026, or
F027, however, the DRE standard is 99.9999% destruction of designated
POHCs. See Sec. 266.104(a).
The DRE standard helps ensure that a combustor is operating under
good combustion practices and thus minimizing emissions of organic HAP.
Under the MACT compliance regime, sources would designate POHCs that
are organic HAP or that are surrogates for organic HAP.
[[Page 21283]]
We propose to establish the RCRA DRE standard as the floor for
existing sources because it is a currently enforceable Federal
standard. There would be no incremental emission reductions associated
with this floor because sources are currently complying with the
standard.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered a beyond-the-floor level for DRE based on use of
better combustion practices but conclude that it may not be replicable
by the best performing sources nor duplicable by other sources given
that we cannot quantify better combustion practices. Moreover, we
cannot ensure that a higher DRE standard would significantly reduce
emissions of organic HAP given that DRE measures the destruction of
organic HAP present in the boiler feed rather than gross emissions of
organic HAP. Although a source's combustion practices may be adequate
to destroy particular organic HAP in the feed, other organic HAP that
may be emitted as products of incomplete combustion may not be
controlled by the DRE standard.\143\
---------------------------------------------------------------------------
\143\ The carbon monoxide/hydrocarbon emission standard would
control organic HAP that are products of incomplete combustion by
also ensuring use of good combustion practices.
---------------------------------------------------------------------------
For these reasons, and after considering non-air quality health and
environmental impacts and energy requirements, we are not proposing a
beyond-the-floor DRE standard for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
We propose to establish the RCRA DRE standard as the floor for new
sources because it is a currently enforceable Federal standard.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
Using the same rationale as we used to consider a beyond-the-floor
DRE standard for existing sources, we conclude that a beyond-the-floor
DRE standard for new sources is not warranted. Consequently, after
considering non-air quality health and environmental impacts and energy
requirements, we are proposing the floor DRE standard for new sources.
XI. How Did EPA Determine the Proposed Emission Standards for Hazardous
Waste Burning Liquid Fuel-Fired Boilers?
The proposed standards for existing and new liquid fuel-fired
boilers that burn hazardous waste are summarized in the table below.
See proposed Sec. 63.1217.
Proposed Standards for Existing and New Liquid Fuel-Fired Boilers
------------------------------------------------------------------------
Emission standard \1\
Hazardous air pollutant or ---------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan: sources 0.40 ng TEQ/dscm.. 0.015 ng TEQ/dscm
equipped with dry air pollution or control of
control system \2\. flue gas
temperature not
to exceed
400[deg]F at the
inlet to the
particulate
matter control
device.
Dioxin and furan: sources 100 ppmv carbon 100 ppmv carbon
equipped with wet or with no monoxide or 10 monoxide or 10
air pollution control systems ppmv hydrocarbons. ppmv hydrocarbons
\2\.
Mercury \3\..................... 3.7E-6 lbs/MM Btu. 3.8E-7 lbs/MM BTU
Particulate matter.............. 72 mg/dscm (0.032 17 mg/dscm (0.0076
gr/dscf). gr/dscf)
Semivolatile metals \3\......... 1.1E-5 lbs/MM BTU. 4.3E-6 lbs/MM BTU
Low volatile metals: chromium 1.1E-4 lbs/MM BTU. 3.6E-5 lbs/MM BTU
only 3, 4.
Hydrogen chloride and chlorine 2.5E-2 lbs/MM BTU 7.2E-4 lbs/MM BTU
gas3, 5. or the or the chlorine
alternative alternative
emission limits emission limits
under Sec. under Sec.
63.1215. 63.1215
Carbon monoxide or hydrocarbons 100 ppmv carbon 100 ppmv carbon
\6\. monoxide or 10 monoxide or 10
ppmv ppmv
hydrocarbons.. hydrocarbons.
Destruction and Removal For existing and new sources, 99.99%
Efficiency. for each principal organic hazardous
constituent (POHC). For sources
burning hazardous wastes F020, F021,
F022, F023, F026, or F027, however,
99.9999% for each POHC.
------------------------------------------------------------------------
\1\ All emission standards are corrected to 7% oxygen, dry basis.
\2\ A wet air pollution system followed by a dry air pollution control
system is not considered to be a dry air pollution control system for
purposes of this standard. A dry air pollution systems followed a wet
air pollution control system is considered to be a dry air pollution
control system for purposes of this standard.
\3\ Standards are expressed as mass of pollutant emissions contributed
by hazardous waste per million Btu contributed by the hazardous waste.
\4\ Standard is for chromium only and does not include arsenic and
beryllium.
\5\ Combined standard, reported as a chloride (Cl(-)) equivalent.
\6\ Hourly rolling average. Hydrocarbons reported as propane.
We considered whether fuel switching could be considered a MACT
floor control technology for liquid fuel-fired boilers to achieve lower
HAP emissions. We conclude that HAP emissions from liquid fuel-fired
boilers are attributable primarily to the hazardous waste fuels rather
than the natural gas or fuel oil that these boilers burn. Consequently,
we conclude that fuel switching is not an effective MACT floor control
technology to reduce HAP emissions for liquid fuel-fired boilers.
A. What Are the Proposed Standards for Dioxin and Furan?
We propose to establish a dioxin/furan standard for existing liquid
fuel-fired boilers equipped with dry air pollution control devices of
0.40 ng TEQ/dscm. The standard for new sources would be 0.015 ng TEQ/
dscm or control of flue gas temperature not to exceed 400 [deg]F at the
inlet to the particulate matter control device. For liquid fuel-fired
boilers equipped either with wet air pollution control systems or with
no air pollution systems, we propose a standard for both existing and
new sources as compliance with the proposed standards for carbon
monoxide/hydrocarbon and destruction and removal efficiency. In
addition, we note that we propose to require a one-time dioxin/furan
emission test for
[[Page 21284]]
sources that would not be subject to a numerical dioxin/furan emission
standard, including liquid fuel-fired boilers with wet or no emission
control device, and new liquid fuel-fired boilers equipped with a dry
air pollution control device. As discussed in Part Two, Section XIV.B
below, the testing would assist in developing both section 112(d)(6)
standards and section 112(f) residual risk standards.
1. What Is the Rationale for the MACT Floor for Existing Sources?
As discussed in Part Two, Section I.B.5, we used a statistical
analysis to conclude that liquid boilers equipped with dry air
pollution control devices have different dioxin/furan emission
characteristics compared to sources with either wet air pollution
control or no air pollution control devices.\144\ Note that we consider
the type of emission control device as a basis for subcategorization
because the type of control device affects formation of dioxin/furan:
dioxin/furan can form in dry particulate matter control devices while
it cannot form in wet (or no) control devices. We therefore believe
subcategorization is warranted and we propose to identify separate
floor levels for sources equipped with dry particulate matter control
devices versus sources with wet or no emission control device.
---------------------------------------------------------------------------
\144\ Sources with a wet air pollution system followed by a dry
air pollution control system is not considered to be a dry air
pollution control system for purposes of this standard. Sources with
a dry air pollution systems followed a wet air pollution control
system is considered to be a dry air pollution control system for
purposes of this standard.
---------------------------------------------------------------------------
a. MACT Floor for Boilers Equipped with Dry Control Systems. To
identify the floor level for liquid fuel boilers equipped with dry air
pollution control systems, we considered whether dioxin/furan can be
controlled by controlling the temperature at the inlet to the
particulate matter control device. We conclude that this control
mechanism may not be the predominant factor that affects dioxin/furan
emissions from these sources. We have emissions data for three boilers
equipped with electrostatic precipitators or fabric filters. Emissions
from two of the boilers are below 0.03 ng TEQ/dscm. We do not have data
on the gas temperature at the inlet to the emission control device for
these sources. The third boiler, however, has dioxin/furan emissions of
2.4 ng TEQ/dscm when the flue gas temperature at the inlet to the
fabric filter is 410 [deg]F. We conclude from this information that
this boiler is not likely to be able to achieve dioxin/furan emissions
below 0.40 ng TEQ/dscm if the gas temperature is reduced to below 400
[deg]F. This is contrary to the finding we made for cement kilns and
incinerators without heat recovery boilers and equipped with dry
particulate matter control devices. In those cases, we conclude that
gas temperature control at the dry particulate matter control device is
the predominant factor affecting dioxin/furan emissions. See
discussions in Sections VII and VIII above. Consequently, other factors
are likely contributing to high dioxin/furan emissions from the liquid
fuel-fired boiler equipped with a fabric filter operated at a gas
temperature of 410 [deg]F, such as metals in the waste feed or soot on
boiler tubes that may catalyze dioxin/furan formation reactions.
We evaluated the compliance test emissions data using the Emissions
Approach and calculated a numerical dioxin/furan floor level of 3.0 ng
TEQ/dscm, which considers emissions variability. As discussed above,
however, one of the three sources for which we have emissions data is
not likely to be able to achieve this emission level using gas
temperature control at the inlet to the dry particulate matter control
device. Consequently, we propose to identify the floor level as 3.0 ng
TEQ/dscm or control of flue gas temperature not to exceed 400 [deg]F at
the inlet to the particulate matter control device. This floor level is
duplicable by all sources, and would minimize dioxin/furan emissions
for sources where flue gas temperature at the control device
substantially affects dioxin/furan emissions. We estimate that this
emission level is being achieved by all sources and, thus, would not
reduce dioxin/furan emissions.
b. MACT Floor for Boilers Equipped with Wet or No Control Systems.
We have dioxin/furan emissions data for 33 liquid fuel-fired boilers
equipped with a wet or no particulate matter control device. Emissions
levels are below 0.1 ng TEQ/dscm for 30 of the sources. Emission levels
for the other three sources are 0.19, 0.36, and 0.44 ng TEQ/dscm.
As previously discussed in Part Two, Section VII.A, we believe that
it would be inappropriate to establish a numerical dioxin/furan
emission floor level for sources using wet or no air pollution control
systems based on the emissions achieved by the best performing sources
because a numerical floor level would not be replicable by the best
performing sources nor duplicable by other sources. As a result, we
propose to define the MACT floor for sources with wet or no emission
control devices as operating under good combustion practices by
complying with the destruction and removal efficiency and carbon
monoxide/hydrocarbon standards.\145\ There would be no emissions
reductions for these existing boilers to comply with the floor level
because they are currently complying with the carbon monoxide/
hydrocarbon standard and destruction and removal efficiency standard
pursuant to RCRA requirements.
---------------------------------------------------------------------------
\145\ The fact that we determined floor control for existing
sources as good combustion practices does not mean that all sources
using floor control will have low dioxin/furan emissions. As
discussed in Part Two, Section XIV.B., we are proposing to require
liquid fuel-fired boilers that would not be subject to a numerical
dioxin/furan emission standard to perform a one-time dioxin/furan
emissions test to quantify the effectiveness of today's proposed
surrogate for dioxin/furan emission control.
---------------------------------------------------------------------------
We also request comment on an alternative MACT floor expressed as a
dioxin/furan emission concentration for liquid fuel boilers with wet or
no emission control devices.\146\ Although it would be inappropriate to
identify a floor concentration based on the average emissions of the
best performing sources as discussed above, we possibly could identify
the floor as the highest emission concentration from any source in our
data base, after considering emissions variability.
---------------------------------------------------------------------------
\146\ Although the floor for liquid fuel boilers equipped with a
dry emission control device would not be a numerical standard (i.e.,
3.0 ng TEQ/dscm or control of temperature of flue gas at the inlet
to the control device to 400 [deg]F), we propose a numerical beyond-
the-floor standard for those boilers, as discussed below in the
text.
---------------------------------------------------------------------------
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated use of activated carbon injection systems or carbon
beds as beyond-the-floor control for further reduction of dioxin/furan
emissions. Activated carbon has been demonstrated for controlling
dioxin/furans in various combustion applications.
a. Beyond-the-Floor Considerations for Boilers Equipped with Dry
Control Systems. For liquid fuel-fired boilers using dry air pollution
control equipment, we evaluated a beyond-the-floor level of 0.40 ng
TEQ/dscm based on activated carbon injection or control of flue gas
temperature not to exceed 400 [deg]F at the inlet to the particulate
matter control device. The national incremental annualized compliance
cost for sources to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $80,000 and would
provide an incremental reduction in dioxin/furan emissions beyond the
MACT floor
[[Page 21285]]
controls of 0.06 grams TEQ per year for a cost-effectiveness of $1.3
million per additional gram of dioxin/furan removed. We evaluated the
nonair quality health and environmental impacts and energy effects of
this beyond-the-floor standard and estimate that the amount of
hazardous waste generated would increase by 100 tons per year, an
additional 25 trillion Btu per year of natural gas would be consumed,
and electricity consumption would increase by 0.50 million kW-hours per
year.
We judge that the cost to achieve this beyond-the-floor level is
warranted given our special concern about dioxin/furan. Dioxin/furan
are some of the most toxic compounds known due to their bioaccumulation
potential and wide range of health effects, including carcinogenesis,
at exceedingly low doses. Exposure via indirect pathways is a chief
reason that Congress singled our dioxin/furan for priority MACT control
in CAA section 112(c)(6). See S. Rep. No. 128, 101st Cong. 1st Sess. at
154-155. In addition, we note that the beyond-the-floor emission level
of 0.40 ng TEQ/dscm is consistent with historically controlled levels
under MACT for hazardous waste incinerators and cement kilns, and
Portland cement plants. See Sec. Sec. 63.1203(a)(1), 63.1204(a)(1),
and 63.1343(d)(3). Also, EPA has determined previously in the 1999
Hazardous Waste Combustor MACT final rule that dioxin/furan in the
range of 0.40 ng TEQ/dscm or less are necessary for the MACT standards
to be considered generally protective of human health under RCRA (using
the 1985 cancer slope factor), thereby eliminating the need for
separate RCRA standards under the authority of RCRA section 3005(c)(3)
and 40 CFR 270.10(k). Finally, we note that this decision is not
inconsistent with EPA's decision not to promulgate beyond-the-floor
standards for dioxin/furan for hazardous waste burning lightweight
aggregate kilns, cement kilns, and incinerators at cost-effectiveness
values in the range of $530,000 to $827,000 per additional gram of
dioxin/furan TEQ removed. See 64 FR at 52892, 52876, and 52961. In
those cases, EPA determined that controlling dioxin/furan emissions
from a level of 0.40 ng TEQ/dscm to a beyond-the-floor level of 0.20 ng
TEQ/dscm was not warranted because dioxin/furan levels below 0.40 ng
TEQ/dscm are generally considered to be below the level of health risk
concern.
For these reasons, we believe that proposing a beyond-the-floor
standard of 0.40 ng TEQ/dscm is warranted notwithstanding the nonair
quality health and environmental impacts and energy effects identified
above and costs of approximately $1.3 million per additional gram of
dioxin/furan TEQ removed. We specifically request comment on our
decision to propose this beyond-the-floor standard.
b. Beyond-the-Floor Considerations for Boilers Equipped with Wet or
No Control Systems. For liquid fuel-fired boilers equipped with wet or
no air pollution control systems, we evaluated a beyond-the-floor level
of 0.20 ng TEQ/dscm based on activated carbon. The national incremental
annualized compliance cost for these sources to meet this beyond-the-
floor level rather than comply with the floor controls would be
approximately $550,000 and would provide an incremental reduction in
dioxin/furan emissions beyond the MACT floor controls of 0.12 grams TEQ
per year. We evaluated the nonair quality health and environmental
impacts and energy effects of this beyond-the-floor standard and
estimate that the amount of hazardous waste generated would increase by
100 tons per year, an additional 25 trillion Btu per year of natural
gas would be consumed, an additional 4 million gallons per year of
water would be used, and electricity consumption would increase by 0.50
million kW-hours per year. We are not proposing a beyond-the-floor
standard of 0.20 ng TEQ/dscm for liquid boilers that use a wet or no
air pollution control system because it would not be cost-effective at
$4.6 million per gram of TEQ removed.
We are also considering an alternative beyond-the-floor standard
for existing liquid fuel boilers with wet or no particulate matter
control devices of 0.40 ng TEQ/dscm. Although all but one source for
which we have data are currently achieving this emission level, boilers
for which we do not have dioxin/furan emissions data may have emissions
higher than 0.40 ng TEQ/dscm. In addition, dioxin/furan emissions from
a given boiler may vary over time. Other factors that may contribute
substantially to dioxin/furan formation, such as the level and type of
soot on boiler tubes, or feeding metals that catalyze dioxin/furan
formation reactions, differ across boilers and may change over time at
a given boiler. Thus, dioxin/furan levels for these sources may be
higher than 0.40 ng TEQ/dscm. For example, we recently obtained dioxin/
furan emissions data for a liquid fuel-fired boiler equipped with a wet
emission control system documenting emissions of 1.4 ng TEQ/dscm.\147\
To control dioxin/furan emissions to a beyond-the-floor standard of
0.40 ng TEQ/dscm, you would use activated carbon. We specifically
request comment on this beyond-the-floor option, including how we
should estimate compliance costs and emissions reductions.
---------------------------------------------------------------------------
\147\ These data were recently obtained and are not in the MACT
data base. See ``Region 4 Boiler Dioxin Data,'' Excel spreadsheet,
March 10, 2004.
---------------------------------------------------------------------------
3. What Is the Rationale for the MACT Floor for New Sources?
The calculated floor level for new liquid fuel boilers equipped
with dry air pollution control systems is 0.015 ng TEQ/dscm, which we
identified using the Emissions Approach. If dioxin/furan emissions
could be controlled predominantly by controlling the gas temperature at
the inlet to the dry particulate matter control device, this would be
the emission level that the single best performing source could be
expected to achieve in 99 out of 100 future tests when operating under
conditions identical to the compliance test conditions during which the
emissions data were obtained. This emission level may not be replicable
by this source and duplicable by other (new) sources, however, because
factors other than flue gas temperature control at the control device
may affect dioxin/furan emissions. See discussion of this issue in the
context of the floor level for existing sources. Therefore, we propose
to establish the floor level as 0.015 ng TEQ/dscm or control of flue
gas temperature not to exceed 400 [deg]F at the inlet to the
particulate matter control device.
As previously discussed, we believe that it would be inappropriate
to establish a numerical dioxin/furan emission floor level for liquid
boilers with wet or with no air pollution control systems. Therefore,
we propose floor control for these units as good combustion practices
provided by complying with the proposed destruction and removal
efficiency and carbon monoxide/hydrocarbon standards.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated use of activated carbon as beyond-the-floor control
for further reduction of dioxin/furan emissions. Activated carbon has
been demonstrated for controlling dioxin/furan in various combustion
applications.
a. Beyond-the-Floor Considerations for Boilers Equipped with Dry
Control Systems. For liquid fuel-fired boilers using dry air pollution
control equipment, we evaluated a beyond-the-floor level of 0.01 ng
TEQ/dscm using activated carbon injection. The national incremental
annualized compliance cost
[[Page 21286]]
for a source with an average gas flowrate to meet this beyond-the-floor
level rather than comply with the floor controls would be approximately
$0.15 million and would provide an incremental reduction in dioxin/
furan emissions beyond the MACT floor controls of 0.005 grams TEQ per
year. We evaluated the nonair quality health and environmental impacts
and energy effects of this beyond-the-floor standard and estimate that,
for a new liquid fuel-fired boiler with average gas flowrate, the
amount of hazardous waste generated would increase by 120 tons per year
and electricity consumption would increase by 0.1 million kW-hours per
year. After considering these impacts and costs of approximately $32
million per additional gram of dioxin/furan removed, we are not
proposing a beyond-the-floor standard of 0.01 ng TEQ/dscm for liquid
fuel-fired boilers using dry air pollution control systems.
We are also considering an alternative beyond-the-floor standard of
0.40 ng TEQ/dscm for new liquid fuel boilers equipped with a dry
particulate matter control device. A new source that achieves the floor
level by controlling the gas temperature at the inlet to the dry
particulate matter control device to 400 [deg]F may have dioxin/furan
emissions at levels far exceeding 0.40 ng TEQ/dscm. See discussion
above regarding factors other than gas temperature at the control
device that can affect dioxin/furan emissions from liquid fuel-fired
boilers (and discussion of emissions of 2.4 ng TEQ/dscm for a boiler
operating a fabric filter at 410 [deg]F). Therefore, it may be
appropriate to establish a beyond-the-floor standard to limit emissions
to 0.40 ng TEQ/dscm based on use of activated carbon injection. We also
note that this beyond-the-floor standard may be appropriate to ensure
that emission levels from new sources do not exceed the proposed 0.40
ng TEQ/dscm beyond-the-floor standard for existing sources. Because
standards for new sources are based on the single best performing
source while standards for existing sources are based on the average of
the best 12% (or best 5) performing sources, standards for new sources
should not be less stringent than standards for existing sources. We
specifically request comment on this beyond-the-floor option, including
how we should estimate compliance costs and emissions reductions.
b. Beyond-the-Floor Considerations for Boilers Equipped with Wet or
No Control Systems. We evaluated a beyond-the-floor level of 0.20 ng
TEQ/dscm for liquid fuel-fired boilers equipped with wet or with no air
pollution control systems based on use of activated carbon. The
national incremental annualized compliance cost for a source with
average gas flowrate to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $0.15 million and
would provide an incremental reduction in dioxin/furan emissions beyond
the MACT floor controls of 0.06 grams TEQ per year. We evaluated the
nonair quality health and environmental impacts and energy effects of
this beyond-the-floor standard and estimate that, for a source with
average gas flowrate, the amount of hazardous waste generated would
increase by 120 tons per year and electricity consumption would
increase by 0.1 million kW-hours per year. After considering these
impacts and costs of approximately $2.4 million per additional gram of
dioxin/furan removed, we are not proposing a beyond-the-floor standard
for liquid fuel-fired boilers using a wet or no air pollution control
system.
We are also considering an alternative beyond-the-floor standard of
0.40 ng TEQ/dscm for new liquid fuel boilers equipped with wet or with
no air pollution control systems. A new source that achieves the floor
level--compliance with the standards for carbon monoxide/hydrocarbon
and destruction and removal efficiency--may have high dioxin/furan
emissions at levels far exceeding 0.40 ng TEQ/dscm. See discussion
above regarding factors other than gas temperature at the control
device that can affect dioxin/furan emissions from liquid fuel-fired
boilers. Therefore, it may be appropriate to establish a beyond-the-
floor standard to limit emissions to 0.40 ng TEQ/dscm based on use of
activated carbon. We specifically request comment on this beyond-the-
floor option, including how we should estimate compliance costs and
emissions reductions.
B. What Is the Rationale for the Proposed Standards for Mercury?
We propose to establish standards for existing liquid fuel-fired
boilers that limit emissions of mercury to 3.7E-6 lbs mercury emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste. The proposed standards for new sources would be 3.8E-7
lbs mercury emissions attributable to the hazardous waste per million
Btu heat input from the hazardous waste.\148\ These standards are
expressed as hazardous waste thermal emission concentrations because
liquid fuel-fired boilers burn hazardous waste for energy recovery. See
discussion in Part Two, Section IV.B of the preamble.
---------------------------------------------------------------------------
\148\ As information, EPA did not propose MACT emission
standards for mercury for liquid fuel-fired boilers that do not burn
hazardous waste. See 68 FR 1660 (Jan. 13, 2003). Note that, in
today's rule, we propose to control mercury only in hazardous waste
fuels, an option obviously not available to boilers that do not burn
hazardous waste.
---------------------------------------------------------------------------
1. What Is the Rationale for the MACT Floor for Existing Sources?
MACT floor for existing sources is 3.7E-6 lbs mercury emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste, which is based primarily by controlling the feed
concentration of mercury in the hazardous waste. Approximately 11% of
liquid boilers also use wet scrubbers that can control emissions of
mercury.
We have normal emissions data within the range of normal emissions
for 32% of the sources.\149\ The normal mercury stack emissions in our
data base are all less than 7 [mu]g/dscm. These emissions are expressed
as mass of mercury (from all feedstocks) per unit of stack gas.
Hazardous waste thermal emissions, available for 12% of sources, range
from 1.0E-7 to 1.0E-5 lbs mercury emissions attributable to the
hazardous waste per million Btu heat input from the hazardous waste.
Hazardous waste thermal emissions represent the mass of mercury
contributed by the hazardous waste per million Btu contributed by the
hazardous waste.
---------------------------------------------------------------------------
\149\ Several owners and operators have used the emissions data
as ``data in lieu of testing'' emissions from other, identical
boilers at the same facility. For purposes of identifying the number
of boilers represented in this paragraph, the percentage includes
the data-in-lieu sources.
---------------------------------------------------------------------------
To identify the MACT floor, we evaluated all normal emissions data
using the Emissions Approach. The calculated floor is 3.7E-6 lbs
mercury emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste. This is an emission level that the
average of the best performing sources could be expected to achieve in
99 of 100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. We estimate that this floor level is being achieved by 40% of
sources and would reduce mercury emissions by 0.68 tons per year.
Because the floor level is based on normal emissions data,
compliance would be documented by complying with a hazardous waste
mercury thermal feed concentration on an annual rolling average. See
discussion in Part Two, Section XIV.F below.
We did not use the SRE/Feed Approach to identify the floor level
because the vast majority of mercury feed levels in the hazardous waste
and
[[Page 21287]]
the emissions measurements did not have detectable concentrations of
mercury. Given that a system removal efficiency, or SRE, is the
percentage of mercury emitted compared to the amount fed, we concluded
that it would be inappropriate to base this analysis on SREs that were
derived from measurements below detectable levels.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of mercury: (1) Activated carbon injection; and (2) control of mercury
in the hazardous waste feed. For reasons discussed below, we are not
proposing a beyond-the-floor standard for mercury.
a. Use of Activated Carbon Injection. We evaluated activated carbon
injection as beyond-the-floor control for further reduction of mercury
emissions. Activated carbon has been demonstrated for controlling
mercury in several combustion applications; however, currently no
liquid fuel boilers burning hazardous waste uses activated carbon
injection. We evaluated a beyond-the-floor level of 1.1E-6 lbs mercury
emissions attributable to the hazardous waste per million Btu heat
input from the hazardous waste. The national incremental annualized
compliance cost for liquid fuel-fired boilers to meet this beyond-the-
floor level rather than comply with the floor controls would be
approximately $12 million and would provide an incremental reduction in
mercury emissions beyond the MACT floor controls of 0.097 tons per
year. We evaluated nonair quality health and environmental impacts and
energy effects of using activated carbon injection to meet this beyond-
the-floor emission level and estimate that the amount of hazardous
waste generated would increase by 4,800 tons per year and that sources
would consume an additional 44 trillion Btu per year of natural gas and
use an additional 9.6 million kW-hours per year beyond the requirements
to achieve the floor level. Therefore, based on these factors and costs
of approximately $124 million per additional ton of mercury removed, we
are not proposing a beyond-the-floor standard based on activated carbon
injection.\150\
---------------------------------------------------------------------------
\150\ We note that the beyond-the-floor dioxin/furan standard we
propose for liquid fuel-fired boilers equipped with dry particulate
matter control devices would also provide no-cost beyond-the-floor
mercury control for sources that use activated carbon injection to
control dioxin/furan. If such sources achieve the beyond-the-floor
dioxin/furan standard by other means (control of temperature at the
inlet to the control device; control of feedrate of metals that may
catalyze formation of dioxin/furan), however, collateral reductions
in mercury emissions would not be realized.
---------------------------------------------------------------------------
b. Feed Control of Mercury in the Hazardous Waste. We also
evaluated a beyond-the-floor level of 3.0E-6 lbs mercury emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste, which represents a 20% reduction from the floor level.
The national incremental annualized compliance cost for liquid fuel-
fired boilers to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $4.2 million and would
provide an incremental reduction in mercury emissions beyond the MACT
floor controls of 0.036 tons per year. Nonair quality health and
environmental impacts and energy effects are not significant factors
for feedrate control. Therefore, based on these factors and costs of
approximately $115 million per additional ton of mercury removed, we
are not proposing a beyond-the-floor standard based on feed control of
mercury in the hazardous waste.
For the reasons discussed above, we do not propose a beyond-the-
floor standard for mercury for existing sources. We propose a standard
based on the floor level: 3.7E-6 lbs mercury emissions attributable to
the hazardous waste per million Btu heat input from the hazardous
waste.
3. What Is the Rationale for the MACT Floor for New Sources?
The MACT floor for new sources for mercury would be 3.8E-7 lbs
mercury emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste and would be implemented as an
annual average because it is based on normal emissions data. This is an
emission level that the single best performing source identified with
the Emissions Approach could be expected to achieve in 99 of 100 future
tests when operating under operating conditions identical to the
compliance test conditions during which the emissions data were
obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated activated carbon injection as beyond-the-floor control
to achieve an emission level of 2.0E-7 lbs mercury emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste. The incremental annualized compliance cost for a new
liquid fuel-fired boiler with average gas flowrate to meet this beyond-
the-floor level, rather than comply with the floor level, would be
approximately $0.15 million and would provide an incremental reduction
in mercury emissions of less than 0.0002 tons per year, for a cost-
effectiveness of $1 billion per ton of mercury removed. We evaluated
the nonair quality health and environmental impacts and energy effects
of this beyond-the-floor standard and estimate that, for a new liquid
fuel-fired boiler with average gas flowrate, the amount of hazardous
waste generated would increase by 120 tons per year and electricity
consumption would increase by 0.1 million kW-hours per year. Although
nonair quality health and environmental impacts and energy effects are
not significant factors, we are not proposing a beyond-the-floor
standard based on activated carbon injection for new sources because it
would not be cost-effective. Therefore, we propose a mercury standard
based on the floor level: 3.8E-7 lbs mercury emissions attributable to
the hazardous waste per million Btu heat input from the hazardous
waste.
C. What Is the Rationale for the Proposed Standards for Particulate
Matter?
The proposed standards for particulate matter for liquid fuel-fired
boilers are 59 mg/dscm (0.026 gr/dscf) for existing sources and 17 mg/
dscm (0.0076 gr/dscf) for new sources.\151\ The particulate matter
standard serves as a surrogate for nonenumerated HAP metal emissions
attributable to the hazardous waste fuel burned in the boiler. Although
the particulate matter standard would also control nonmercury HAP metal
from nonhazardous waste fuels, the natural gas or fuel oil these
boilers burn as primary or auxiliary fuel do not contain significant
levels of metal HAP.
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\151\ As information, EPA proposed MACT standards for
particulate matter for solid fuel-fired industrial, commercial, and
institutional boilers that do not burn hazardous waste of 0.035 gr/
dscf for existing sources and 0.013 gr/dscf for new sources.
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1. What Is the Rationale for the MACT Floor for Existing Sources?
Few liquid fuel-fired boilers are equipped particulate matter
control equipment such as electrostatic precipitators and baghouses,
and, therefore, many sources control particulate matter emissions by
limiting the ash content of the hazardous waste. We have compliance
test emissions data from nearly all liquid boilers representing maximum
allowable emissions. Particulate emissions range from 0.0008 to 0.078
gr/dscf.
To identify the floor level, we evaluated the compliance test
emissions
[[Page 21288]]
data associated with the most recent test campaign using the APCD
Approach. The calculated floor is 72 mg/dscm (0.032 gr/dscf), which
considers emissions variability. This is an emission level that the
average of the performing sources could be expected to achieve in 99 of
100 future tests when operating under operating conditions identical to
the compliance test conditions during which the emissions data were
obtained. We estimate that this floor level is being achieved by 44% of
sources and would reduce particulate matter emissions by 1,200 tons per
year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated use of fabric filters to improve particulate matter
control to achieve a beyond-the-floor standard of 36 mg/dscm (0.016 gr/
dscf). The national incremental annualized compliance cost for liquid
fuel-fired boilers to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $16 million and
would provide an incremental reduction in particulate matter emissions
beyond the MACT floor controls of 520 tons per year. We evaluated the
nonair quality health and environmental impacts and energy effects of
this beyond-the-floor standard and estimate that the amount of
hazardous waste generated would increase by 520 tons per year and
electricity consumption would increase by 13 million kW-hours per year.
After considering these factors and costs of approximately $30,000 per
additional ton of particulate matter removed, we are not proposing a
beyond-the-floor standard.
For the reasons discussed above, we propose a standard for
particulate matter for existing liquid fuel-fired boilers based on the
floor level: 72 mg/dscm (0.032 gr/dscf).
3. What Is the Rational for the MACT Floor for New Sources?
MACT floor for new sources would be 17 mg/dscm (0.0076 gr/dscf),
considering emissions variability. This is an emission level that the
single best performing source identified by the APCD Approach (i.e.,
the source using a fabric filter \152\ with the lowest emissions) could
be expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained.
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\152\ The source also is equipped with a high efficiency
particulate air (HEPA) filter.
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4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated use of an advanced fabric filter using high efficiency
membrane bag material and a low air to cloth ratio to achieve a beyond-
the-floor emission level of 9 mg/dscm (0.0040 gr/dscf). The incremental
annualized cost for a new liquid fuel-fired boiler with average gas
flowrate to meet this beyond-the-floor level, rather than comply with
the floor level, would be approximately $0.15 million and would provide
an incremental reduction in particulate emissions of approximately 2.9
tons per year, for a cost-effectiveness of $53,000 per ton of
particulate matter removed. We evaluated the nonair quality health and
environmental impacts and energy effects of this beyond-the-floor
standard and estimate that, for a new liquid fuel-fired boiler with
average gas flowrate, the amount of hazardous waste generated would
increase by 3 tons per year and electricity consumption would increase
by 0.54 million kW-hours per year. Considering these factors and cost-
effectiveness, we conclude that a beyond-the-floor standard of 9 mg/
dscm is not warranted.
For the reasons discussed above, we propose a floor-based standard
for particulate matter for new liquid fuel-fired boilers: 9.8 mg/dscm
(0.0043 gr/dscf)
D. What Is the Rationale for the Proposed Standards for Semivolatile
Metals?
We propose a standard for existing liquid fuel-fired boilers that
limits emissions of semivolatile metals (cadmium and lead, combined) to
1.1E-5 lbs semivolatile metals emissions attributable to the hazardous
waste per million Btu heat input from the hazardous waste. The proposed
standard for new sources is 4.3E-6 lbs semivolatile metals emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste.
1. What Is the Rationale for the MACT Floor for Existing Sources?
MACT floor for existing sources is 1.1E-5 lbs semivolatile metals
emissions attributable to the hazardous waste per million Btu heat
input of the hazardous waste, which is based on particulate matter
control (for those few sources using a control device) and controlling
the feedrate of semivolatile metals in the hazardous waste.
We have emissions data within the range of normal emissions for
nearly 40% of the sources.\153\ The normal semivolatile stack emissions
in our database range from less than 1 to 46 ug/dscm. These emissions
are expressed conventionally as mass of semivolatile metals (from all
feedstocks) per unit of stack gas. Hazardous waste thermal emissions,
available for 25% of sources, range from 1.2E-6 to 4.8E-5 lbs
semivolatile metals emissions attributable to the hazardous waste per
million Btu heat input of the hazardous waste.
---------------------------------------------------------------------------
\153\ Several owners and operators have used the emissions data
as ``data in lieu of testing'' emissions from other, identical
boilers at the same facility. For purposes of identifying the number
of boilers represented in this paragraph, the percentages include
the data-in-lieu sources.
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We identified a MACT floor of 1.1E-5 expressed as a hazardous waste
thermal emission by applying the Emissions Approach to the normal
hazardous waste thermal emissions data.\154\ This is an emission level
that the average of the best performing sources could be expected to
achieve in 99 of 100 future tests when operating under conditions
identical to the compliance test conditions during which the emissions
data were obtained. We estimate that this floor level is being achieved
by 33% of sources and would reduce semivolatile metals emissions by 1.7
tons per year.
---------------------------------------------------------------------------
\154\ We propose to use the Emissions Approach rather than the
SRE/Feed approach because our data base is comprised of emissions
obtained during normal rather than compliance test operations.
Because of the relatively low semivolatile metal feedrates during
normal operations, we are concerned that the system removal
efficiencies that we would calculate may be inaccurate (e.g.,
sampling and analysis imprecision at low feed rates can have a
substantial impact on calculated system removal efficiencies).
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Because the floor level is based on normal emissions data,
compliance would be documented by complying with a hazardous waste
mercury thermal feed concentration on an annual rolling average. See
discussion in Part Two, Section XIV.F below.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of semivolatile metals: (1) Improved particulate matter control; and
(2) control of mercury in the hazardous waste feed. For reasons
discussed below, we are not proposing a beyond-the-floor standard for
semivolatile metals.
a. Improved Particulate Matter Control. We evaluated installation
of a new fabric filter or improved design, operation, and maintenance
of the existing electrostatic precipitator and fabric filter as beyond-
the-floor control
[[Page 21289]]
for further reduction of semivolatile metals emissions. We evaluated a
beyond-the-floor level of 5.5E-6 lbs semivolatile metals emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste. The national incremental annualized compliance cost
for liquid fuel-fired boilers to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $6.5
million and would provide an incremental reduction in semivolatile
metals emissions beyond the MACT floor controls of 0.06 tons per year.
We evaluated nonair quality health and environmental impacts and energy
effects and determined that this beyond-the-floor option would increase
the amount of hazardous waste generated by approximately 45 tons per
year and would increase electricity usage by 0.8 million kW-hours per
year. After considering these factors and costs of approximately $100
million per additional ton of semivolatile metals removed, we are not
proposing a beyond-the-floor standard based on improved particulate
matter control.
b. Feed Control of Semivolatile Metals in the Hazardous Waste. We
also evaluated a beyond-the-floor level of 8.8E-6 lbs semivolatile
metals emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste, which represents a 20% reduction
from the floor level. The national incremental annualized compliance
cost for liquid fuel-fired boilers to meet this beyond-the-floor level
rather than comply with the floor controls would be approximately $4.8
million and would provide an incremental reduction in semivolatile
metals emissions beyond the MACT floor controls of 0.06 tons per year.
Nonair quality health and environmental impacts and energy effects are
not significant factors for feedrate control. Therefore, considering
these factors and costs of approximately $81 million per additional ton
of semivolatile metals removed, we are not proposing a beyond-the-floor
standard based on feed control of semivolatile metals in the hazardous
waste.
For the reasons discussed above, we propose a floor standard for
semivolatile metals for existing liquid fuel-fired boilers of 1.1E-5
lbs semivolatile metals emissions attributable to the hazardous waste
per million Btu heat input from the hazardous waste.
3. What Is the Rationale for the MACT Floor for New Sources?
The MACT floor for new sources for semivolatile metals would be
4.3E-6 lbs semivolatile metals emissions attributable to the hazardous
waste per million Btu heat input from the hazardous waste. This is an
emission level that the single best performing source identified with
the Emissions Approach \155\ could be expected to achieve in 99 of 100
future tests when operating under operating conditions identical to the
compliance test conditions during which the emissions data were
obtained.
---------------------------------------------------------------------------
\155\ We use the Emissions Approach rather than the SRE/Feed
Approach when we use normal rather than compliance test data to
establish the standard, as discussed previously.
---------------------------------------------------------------------------
Because the floor level is based on normal emissions data,
compliance would be documented by complying with a hazardous waste
mercury thermal feed concentration on an annual rolling average. See
discussion in Part Two, Section XIV.F below.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated a beyond-the-floor level of 2.1E-6 lbs semivolatile
metals emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste based on an advanced fabric filter
using high efficiency membrane bag material and a low air to cloth
ratio. The incremental annualized compliance cost for a new liquid
fuel-fired boiler with average gas flowrate to meet this beyond-the-
floor level, rather than comply with the floor level, would be
approximately $0.15 million and would provide an incremental reduction
in semivolatile metals emissions of less than 0.002 tons per year, for
a cost-effectiveness of $87 million per ton of semivolatile metals
removed. We evaluated the nonair quality health and environmental
impacts and energy effects of this beyond-the-floor standard and
estimate that, for a new liquid fuel-fired boiler with average gas
flowrate, the amount of hazardous waste generated would increase by 2
tons per year and electricity consumption would increase by 0.54
million kW-hours per year. Considering these factors and cost-
effectiveness, we conclude that a beyond-the-floor standard is not
warranted. Therefore, we propose a semivolatile metals standard based
on the floor level: 4.3E-6 lbs semivolatile metals emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste for new sources.
E. What Is the Rationale for the Proposed Standards for Chromium?
We propose to establish standards for existing and new liquid fuel-
fired boilers that limit emissions of chromium to 1.1E-4 lbs and 3.6E-5
lbs chromium emissions attributable to the hazardous waste per million
Btu heat input from the hazardous waste, respectively.
We propose to establish emission standards on chromium-only because
our data base has very limited compliance test data on emissions of
total low volatile metals: arsenic, beryllium, and chromium. We have
compliance test data on only two sources for total low volatile metals
emissions while we have compliance test data for 12 sources for
chromium-only. Although we have total low volatile metals emissions for
12 sources when operating under normal operations, we prefer to use
compliance test data to establish the floor because they better address
emissions variability.
By establishing a low volatile metal floor based on chromium
emissions only we are relying on the particulate matter standard to
control the other enumerated low volatile metals--arsenic and
beryllium--as well as nonenumerated metal HAP. We request comment on
this approach and note that, as discussed below, an alternative
approach would be to establish a MACT floor based on normal emissions
data for all three enumerated low volatile metals.
We request comment on whether the compliance test data for
chromium-only are appropriate for establishing a MACT floor for
chromium. We are concerned that some sources in our data base may have
used chromium as a surrogate for arsenic and beryllium during RCRA
compliance testing such that their chromium emissions may be more
representative of their total low volatile metals emissions than only
chromium. If we determine this to be the case, we could apply the floor
we calculate using chromium emissions to total low volatile metal
emissions. Alternatively, we could use the normal emissions data we
have on 12 sources and our MACT methodology to establish a total low
volatile metals floor.
1. What Is the Rationale for the MACT Floor for Existing Sources?
MACT floor for existing sources is 1.1E-4 lbs chromium emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste, which is based on particulate matter control (for
those few sources using a control device) and controlling the feed
concentration of chromium in the hazardous waste.
We have compliance test emissions data for approximately 17% of the
[[Page 21290]]
sources.\156\ The compliance test chromium stack emissions in our
database range from 2 to 900 ug/dscm. These emissions are expressed as
mass of chromium (from all feedstocks) per unit of stack gas. Hazardous
waste thermal emissions, available for 13% of sources, range from 3.2E-
6 to 8.8E-4 lbs chromium emissions attributable to the hazardous waste
per million Btu heat input from the hazardous waste.
---------------------------------------------------------------------------
\156\ Several owners and operators have used the emissions data
as ``data in lieu of testing'' emissions from other, identical
boilers at the same facility. For purposes of identifying the number
of boilers represented in this paragraph, the percentages include
the data-in-lieu sources.
---------------------------------------------------------------------------
To identify the floor level, we evaluated all compliance test
thermal emissions data using the SRE/Feed Approach (see discussion in
Section VI.C above). The calculated floor is 1.1E-4 lbs chromium
emissions attributable to the hazardous waste per million Btu heat
input from the hazardous waste feed, which considers emissions
variability. This is an emission level that the average of the best
performing sources could be expected to achieve in 99 of 100 future
tests when operating under conditions identical to the compliance test
conditions during which the emissions data were obtained. We estimate
that this floor level is being achieved by 36% of sources and would
reduce chromium emissions by 9.4 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of chromium emissions: (1) Use of a fabric filter to improve
particulate matter control; and (2) control of chromium in the
hazardous waste feed. For reasons discussed below, we are not proposing
a beyond-the-floor standard for chromium.
a. Use of a Fabric Filter to Improve Particulate Matter Control. We
evaluated use of a fabric filter as beyond-the-floor control for
further reduction of chromium emissions. We evaluated a beyond-the-
floor level of 5.5E-5 lbs chromium emissions attributable to the
hazardous waste per million Btu heat input from the hazardous waste.
The national incremental annualized compliance cost for liquid fuel-
fired boilers to meet this beyond-the-floor level rather than comply
with the floor controls would be approximately $5.9 million and would
provide an incremental reduction in chromium emissions beyond the MACT
floor controls of 0.50 tons per year. We evaluated nonair quality
health and environmental impacts and energy effects and determined that
this beyond-the-floor option would increase the amount of hazardous
waste generated by approximately 160 tons per year and would increase
electricity usage by 3.0 million kW-hours per year. Based on these
impacts and a cost of approximately $12 million per additional ton of
chromium removed, we are not proposing a beyond-the-floor standard
based on improved particulate matter control.
b. Feed Control of Chromium in the Hazardous Waste. We evaluated
additional feed control of chromium in the hazardous waste as a beyond-
the-floor control technique to reduce floor emission levels by 25% to
achieve a standard of 8.8E-5 lbs chromium emissions attributable to the
hazardous waste per million Btu heat input from the hazardous waste.
This beyond-the-floor level of control would reduce chromium by an
additional 0.20 tons per year at a cost-effectiveness of $22 million
per ton of chromium removed. Nonair quality health and environmental
impacts and energy effects are not significant factors for feedrate
control. We conclude that use of additional hazardous waste chromium
feedrate control would not be cost-effective and are not proposing a
beyond-the-floor standard based on this control technique.
For the reasons discussed above, we do not propose a beyond-the-
floor standard for chromium. Consequently, we propose to establish the
emission standard for existing liquid fuel-fired boilers at the floor
level: a hazardous waste thermal emission standard of 1.1E-4 lbs
chromium emissions attributable to hazardous waste per million Btu of
hazardous waste feed.
3. What Is the Rationale for the MACT Floor for New Sources?
The MACT floor for new sources for chromium would be 3.6E-5 lbs
chromium emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste feed. This is an emission level
that the single best performing source identified with the SRE/Feed
Approach could be expected to achieve in 99 of 100 future tests when
operating under operating conditions identical to the compliance test
conditions during which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated use of an advanced fabric filter using high efficiency
membrane bag material and a low air to cloth ratio as beyond-the-floor
control to reduce chromium emissions to a beyond-the-floor level of
1.8E-5 lbs chromium emissions attributable to the hazardous waste per
million Btu heat input from the hazardous waste. The incremental
annualized compliance cost for a new liquid fuel-fired boiler with
average gas flowrate to meet this beyond-the-floor level, rather than
comply with the floor level, would be approximately $0.15 million and
would provide an incremental reduction in chromium emissions of 0.014
tons per year, for a cost-effectiveness of $11 million per ton of
chromium removed. We evaluated the nonair quality health and
environmental impacts and energy effects of this beyond-the-floor
standard and estimate that, for a new liquid fuel-fired boiler with
average gas flowrate, the amount of hazardous waste generated would
increase by 2 tons per year and electricity consumption would increase
by 0.54 million kW-hours per year. Considering these factors and cost-
effectiveness, we conclude that a beyond-the-floor standard is not
warranted. Therefore, we propose a chromium emission standard for new
sources based on the floor level: 3.6E-5 lbs chromium emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste feed.
F. What Is the Rationale for the Proposed Standards for Total Chlorine?
We are proposing to establish a standard for existing liquid fuel-
fired boilers that limit emissions of hydrogen chloride and chlorine
gas (i.e., total chlorine) to 2.5E-2 lbs total chlorine emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste. The proposed standard for new sources would be 7.2E-4
lbs total chlorine emissions attributable to the hazardous waste per
million Btu heat input from the hazardous waste.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Most liquid fuel-fired boilers that burn hazardous waste do not
have back-end controls such as wet scrubbers for total chlorine
control. For these sources, total chlorine emissions are controlled by
most sources by controlling the feedrate of chlorine in the hazardous
waste feed. Approximately 15% of sources use wet scrubbing systems to
control total chlorine emissions.
We have compliance test data representing maximum emissions for 40%
of the boilers. Total chlorine emissions range from less than 1 to 900
ppmv. Hazardous waste thermal emissions, available for 27% of boilers,
range from 1.00E-4 to 1.4 lbs total
[[Page 21291]]
chlorine emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste.
The calculated floor is 2.5E-2 lbs total chlorine emissions
attributable to the hazardous waste per million Btu heat input from the
hazardous waste using the SRE/Feed Approach to identify the best
performing sources (see discussion in section VI.C above). This is an
emission level that the average of the performing sources could be
expected to achieve in 99 of 100 future tests when operating under
operating conditions identical to the compliance test conditions during
which the emissions data were obtained. We estimate that this floor
level is being achieved by 70% of sources and would reduce total
chlorine emissions by 660 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We identified two potential beyond-the-floor techniques for control
of total chlorine emissions: (1) Use of a wet scrubber; and (2) control
of chlorine in the hazardous waste feed. For reasons discussed below,
we are not proposing a beyond-the-floor standard for total chlorine.
a. Use of Wet Scrubbing. We considered a beyond-the-floor standard
of 1.3E-2 lbs total chlorine emissions attributable to the hazardous
waste per million Btu heat input from the hazardous waste based on wet
scrubbing to reduce emissions beyond the floor level by 50 percent. The
national incremental annualized compliance cost for liquid fuel-fired
boilers to meet this beyond-the-floor level rather than comply with the
floor controls would be approximately $7.8 million and would provide an
incremental reduction in total chlorine emissions beyond the MACT floor
controls of 430 tons per year. We evaluated nonair quality health and
environmental impacts and energy effects and determined that this
beyond-the-floor option would increase both the amount of hazardous
wastewater generated and water usage by approximately 3.2 billion
gallons per year and would increase electricity usage by 30 million kW-
hours per year. Considering these impacts and a cost-effectiveness of
approximately $18,000 per additional ton of total chlorine removed, we
are not proposing a beyond-the-floor standard based on wet scrubbing.
b. Feed Control of Chlorine in the Hazardous Waste. We evaluated
additional feed control of chlorine in the hazardous waste as a beyond-
the-floor control technique to reduce floor emission levels by 20% to
achieve a standard of 2.0E-2 lbs total chlorine emissions attributable
to the hazardous waste per million Btu heat input from the hazardous
waste. The national incremental annualized compliance cost for liquid
fuel-fired boilers to meet this beyond-the-floor level rather than
comply with the floor controls would be approximately $3.9 million and
would provide an incremental reduction in total chlorine emissions
beyond the MACT floor controls of 170 tons per year. Nonair quality
health and environmental impacts and energy effects are not significant
factors for feedrate control. We conclude that use of additional
hazardous waste chlorine feedrate control would not be cost-effective
at $23,000 per ton of total chlorine removed and are not proposing a
beyond-the-floor standard based on this control technique.
For the reasons discussed above, we propose a total chlorine
standard for existing liquid fuel-fired boilers based on the floor
level: 2.5E-2 lbs total chlorine emissions attributable to the
hazardous waste per million Btu heat input from the hazardous waste.
3. What Is the Rationale for the MACT Floor for New Sources?
The MACT floor for new sources for total chlorine would be 7.2E-4
lbs total chlorine emissions attributable to the hazardous waste per
million Btu heat input from the hazardous waste. This is an emission
level that the single best performing source identified with the SRE/
Feed Approach could be expected to achieve in 99 of 100 future tests
when operating under operating conditions identical to the compliance
test conditions during which the emissions data were obtained.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated wet scrubbing as beyond-the-floor control for further
reductions in total chlorine emissions to achieve a beyond-the-floor
level of 3.6E-4 lbs total chlorine emissions attributable to the
hazardous waste per million Btu heat input from the hazardous waste.
The incremental annualized compliance cost for a new liquid fuel-fired
boiler with an average gas flowrate to meet this beyond-the-floor
level, rather than comply with the floor level, would be approximately
$0.44 million and would provide an incremental reduction in total
chlorine emissions of approximately 0.13 tons per year, for a cost-
effectiveness of $3.3 million per ton of total chlorine removed. We
evaluated nonair quality health and environmental impacts and energy
effects and determined that, for a new source with average an average
gas flowrate, this beyond-the-floor option would increase both the
amount of hazardous wastewater generated and water usage by
approximately 140 million gallons per year and would increase
electricity usage by 1.3 million kW-hours per year. After considering
these impacts and cost-effectiveness, we conclude that a beyond-the-
floor standard based on wet scrubbing for new liquid fuel-fired boilers
is not warranted.
For the reasons discussed above, we propose a total chlorine
standard for new sources based on the floor level: 7.2E-4 lbs total
chlorine emissions attributable to the hazardous waste per million Btu
heat input from the hazardous waste.
G. What Is the Rationale for the Proposed Standards for Carbon Monoxide
or Hydrocarbons?
To control emissions of organic HAP, existing and new sources would
be required to comply with either a carbon monoxide standard of 100
ppmv or a hydrocarbon standard of 10 ppmv.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Liquid fuel-fired boilers that burn hazardous waste are currently
subject to RCRA standards that require compliance with either a carbon
monoxide standard of 100 ppmv, or a hydrocarbon standard of 20 ppmv.
Compliance is based on an hourly rolling average as measured with a
CEMS. See Sec. 266.104(a). We are proposing today floor standards of
100 ppmv for carbon monoxide or 10 ppmv for hydrocarbons.
Floor control for existing sources is operating under good
combustion practices including: (1) Providing adequate excess air with
use of oxygen CEMS and feedback air input control; (2) providing
adequate fuel/air mixing; (3) homogenizing hazardous waste fuels (such
as by blending or size reduction) to control combustion upsets due to
very high or very low volatile content wastes; (4) regulating waste and
air feedrates to ensure proper combustion temperature and residence
time; (5) characterizing waste prior to burning for combustion-related
composition (including parameters such as heating value, volatile
content, liquid waste viscosity, etc.); (6) ensuring the source is
operated by qualified, experienced operators; and (7) periodic
inspection and maintenance of combustion system components such as
burners, fuel and air supply lines, injection nozzles, etc. Given that
there are many interdependent parameters that affect combustion
efficiency and thus carbon
[[Page 21292]]
monoxide and hydrocarbon emissions, we are not able to quantify ``good
combustion practices.''
All liquid fuel-fired boilers are currently complying with the RCRA
carbon monoxide limit of 100 ppmv on an hourly rolling average. No
boilers are complying with the RCRA hydrocarbon limit of 20 ppmv on an
hourly rolling average.
We propose a floor level for carbon monoxide level of 100 ppmv
because it is a currently enforceable Federal standard. Although the
best performing sources are achieving carbon monoxide levels below 100
ppmv, it is not appropriate to establish a lower floor level because
carbon monoxide is a surrogate for nondioxin/furan organic HAP. As
such, lowering the carbon monoxide floor may not significantly reduce
organic HAP emissions. In addition, it would be inappropriate to apply
a MACT methodology to the carbon monoxide emissions from the best
performing sources because those sources may not be able to replicate
their emission levels. This is because there are myriad factors that
affect combustion efficiency and, subsequently, carbon monoxide
emissions. Extremely low carbon monoxide emissions cannot be assured by
controlling only one or two operating parameters We note also that we
used this rationale to establish a carbon monoxide standard of 100 ppmv
for Phase I sources in the September 1999 Final Rule.
We propose a floor level for hydrocarbons of 10 ppmv even though
the currently enforceable standard is 20 ppmv because: (1) The two
sources that comply with the RCRA hydrocarbon standard can readily
achieve 10 ppmv; and (2) reducing hydrocarbon emissions within the
range of 20 ppmv to 10 ppmv should reduce emissions of nondioxin/furan
organic HAP. We do not apply a prescriptive MACT methodology to
establish a hydrocarbon floor below 10 ppmv, however, because we have
data from only two sources. In addition, we note that the hydrocarbon
emission standard for Phase I sources established in the September 1999
Final Rule is 10 ppmv also.
There would be no incremental emission reductions associated with
these floors because all sources are currently achieving the floor
levels.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered beyond-the-floor levels for carbon monoxide and
hydrocarbons based on use of better combustion practices but conclude
that they may not be replicable by the best performing sources nor
duplicable by other sources given that we cannot quantify good
combustion practices. Moreover, as discussed above, we cannot ensure
that lower carbon monoxide or hydrocarbon levels would significantly
reduce emissions of nondioxin/furan organic HAP.
Nonair quality health and environmental impacts and energy
requirements are not significant factors for use of better combustion
practices as beyond-the-floor control.
For these reasons, we conclude that beyond-the-floor standards for
carbon monoxide and hydrocarbons are not warranted for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be the same as the floor for
existing sources--100 ppmv for carbon monoxide and 10 ppmv for
hydrocarbons--and based on the same rationale.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
As discussed in the context of beyond-the-floor considerations for
existing sources, we considered beyond-the-floor standards for carbon
monoxide and hydrocarbons for new sources based on use of better
combustion practices. But we conclude that beyond the floor standards
may not be replicable by the best performing sources nor duplicable by
other sources given that we cannot quantify good combustion practices.
Moreover, we cannot ensure that lower carbon monoxide or hydrocarbon
levels would significantly reduce emissions of nondioxin/furan organic HAP.
Nonair quality health and environmental impacts and energy
requirements are not significant factors for use of better combustion
practices as beyond-the-floor control.
For these reasons, we are not proposing a beyond-the-floor standard
for carbon monoxide and hydrocarbons.
H. What Is the Rationale for the Proposed Standard for Destruction and
Removal Efficiency?
To control emissions of organic HAP, existing and new sources would
be required to comply with a destruction and removal efficiency (DRE)
of 99.99% for organic HAP. For sources burning hazardous wastes F020,
F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999%
for organic HAP.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Liquid fuel-fired boilers that burn hazardous waste are currently
subject to RCRA DRE standards that require 99.99% destruction of
designated principal organic hazardous constituents (POHCs). For
sources that burn hazardous wastes F020, F021, F022, F023, F026, or
F027, however, the DRE standard is 99.9999% destruction of designated
POHCs. See Sec. 266.104(a).
The DRE standard helps ensure that a combustor is operating under
good combustion practices and thus minimizing emissions of organic HAP.
Under the MACT compliance regime, sources would designate POHCs that
are organic HAP or that are surrogates for organic HAP.
We propose to establish the RCRA DRE standard as the floor for
existing sources because it is a currently enforceable Federal
standard. There would be no incremental costs or emission reductions
associated with this floor because sources are currently complying with
the standard.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered a beyond-the-floor level for DRE based on use of
better combustion practices but conclude that it may not be replicable
by the best performing sources nor duplicable by other sources given
that we cannot quantify better combustion practices. Moreover, we
cannot ensure that a higher DRE standard would significantly reduce
emissions of organic HAP given that DRE measures the destruction of
organic HAP present in the boiler feed rather than gross emissions of
organic HAP. Although a source's combustion practices may be adequate
to destroy particular organic HAP in the feed, other organic HAP that
may be emitted as products of incomplete combustion may not be
controlled by the DRE standard.\157\
---------------------------------------------------------------------------
\157\ The carbon monoxide/hydrocarbon emission standard would
control organic HAP that are products of incomplete combustion by
also ensuring use of good combustion practices.
---------------------------------------------------------------------------
For these reasons, and after considering nonair quality health and
environmental impacts and energy requirements, we are not proposing a
beyond-the-floor DRE standard for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
We propose to establish the RCRA DRE standard as the floor for new
sources because it is a currently enforceable Federal standard.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
Using the same rationale as we used to consider a beyond-the-floor
DRE
[[Page 21293]]
standard for existing sources, we conclude that a beyond-the-floor DRE
standard for new sources is not warranted. Consequently, after
considering nonair quality health and environmental impacts and energy
requirements, we are proposing the floor DRE standard for new sources.
XII. How Did EPA Determine the Proposed Emission Standards for
Hazardous Waste Burning Hydrochloric Acid Production Furnaces?
The proposed standards for existing and new hydrochloric acid
production furnaces that burn hazardous waste are summarized in the
table below. See proposed Sec. 63.1218.
Proposed Standards for Existing and New Hydrochloric Acid Production
Furnaces
------------------------------------------------------------------------
Emission standard\1\
Hazardous air pollutant or -------------------------------------------
surrogate Existing sources New sources
------------------------------------------------------------------------
Dioxin and furan............ 0.40 ng TEQ/dscm.... 0.40 ng TEQ/dscm.
Hydrochloric acid and 14 ppmv or 99.9927% 1.2 ppmv or
chlorine gas \2\. System Removal 99.99937% System
Efficiency. Removal Efficiency.
Carbon monoxide or 100 ppmv carbon 100 ppmv carbon
hydrocarbons \3\. monoxide or 10 ppmv monoxide or 10 ppmv
hydrocarbons. hydrocarbons.
Destruction and Removal For existing and new sources, 99.99% for
Efficiency. each principal organic hazardous
constituent (POHC). For sources burning
hazardous wastes F020, F021, F022, F023,
F026, or F027, however, 99.9999% for each
POHC.
------------------------------------------------------------------------
\1\ All emission standards are corrected to 7% oxygen, dry basis.
\2\ Combined standard, reported as a chloride (Cl(-)) equivalent.
\3\ Hourly rolling average. Hydrocarbons reported as propane.
A. What Is the Rationale for the Proposed Standards for Dioxin and
Furan?
The proposed standard for dioxin/furan for existing and new sources
is 0.40 ng TEQ/dscm.
1. What Is the Rationale for the MACT Floor for Existing Sources?
The proposed MACT floor for existing sources is compliance with the
proposed CO/HC emission standard and compliance with the proposed DRE
standard.
Hydrochloric acid production furnaces use wet scrubbers to remove
hydrochloric acid from combustion gases to produce the hydrochloric
acid product and to minimize residual emissions of hydrochloric acid
and chlorine gas. Thus, dioxin/furan cannot be formed on particulate
surfaces in the emission control device as can happen with
electrostatic precipitators and fabric filters. Nonetheless, dioxin/
furan emissions from hydrochloric acid production furnaces can be very
high. We have dioxin/furan emissions data for 18 test conditions
representing 14 of the 17 sources. Dioxin/furan emissions range from
0.02 ng TEQ/dscm to 6.8 ng TEQ/dscm.
We investigated whether it would be appropriate to establish
separate dioxin/furan standards for furnaces equipped with waste heat
recovery boilers versus those without boilers. Ten of the 17
hydrochloric acid production furnaces are equipped with boilers. We
considered whether waste heat recovery boilers may be causing the
elevated dioxin/furan emissions, as appeared to be the case for
incinerators equipped with boilers. See 62 FR at 24220 (May 2, 1997)
where we explain that heat recovery boilers preclude rapid temperature
quench of combustion gases, thus allowing particle-catalyzed formation
of dioxin/furan. The dioxin/furan data for hydrochloric acid production
furnaces indicate, however, that furnaces with boilers have dioxin/
furan emissions ranging from 0.05 to 6.8 ng TEQ/dscm, while furnaces
without boilers have dioxin/furan emissions ranging from 0.02 to 1.7 ng
TEQ/dscm. Based on a statistical analysis of the data sets (see
discussion in Part Two, Section II.E), we conclude that the dioxin/
furan emissions for furnaces equipped with boilers are not
significantly different from dioxin/furan emissions for furnaces
without boilers. Thus, we conclude that separate dioxin/furan emission
standards are not warranted.
We cannot identify or quantify a dioxin/furan control mechanism for
these furnaces. Consequently, we conclude that establishing a floor
emission level based on emissions from the best performing sources
would not be appropriate because the best performing sources may not be
able to replicate their emission levels, and other sources may not be
able to duplicate those emission levels.
We note, however, that dioxin/furan emissions can be affected by
the furnace's combustion efficiency. Operating under poor combustion
conditions can generate dioxin/furan and organic precursors that may
contribute to post-combustion dioxin/furan formation. Because we cannot
quantify a dioxin/furan floor level and because hydrochloric acid
production furnaces are currently required to operate under good
combustion practices by RCRA standards for carbon monoxide/hydrocarbons
and destruction and removal efficiency, we identify those RCRA
standards as the proposed MACT floor. See Sec. 266.104 requiring
compliance with destruction and removal efficiency and carbon monoxide/
hydrocarbon emission standards.\158\ We also find, as required by CAA
section 112(h)(1), that these proposed standards are consistent with
section 112(d)'s objective of reducing emissions of these HAP to the
extent achievable.
---------------------------------------------------------------------------
\158\ Section 266.104 requires compliance with a carbon monoxide
limit of 100 ppmv or a hydrocarbon limit of 20 ppmv, while we are
proposing today a carbon monoxide limit of 100 ppmv or a hydrocarbon
limit of 10 ppmv (see Section XII.H in the text). Although today's
proposed hydrocarbon limit is more stringent than the current limit
for hydrochloric acid production furnaces, all sources chose to
comply with the 100 ppmv carbon monoxide limit.
---------------------------------------------------------------------------
We also request comment on an alternative MACT floor expressed as a
dioxin/furan emission concentration. Although it would be inappropriate
to identify a floor concentration based on the average emissions of the
best performing sources as discussed above, we could identify the floor
as the highest emission concentration from any source in our data base,
after considering emissions variability. Under this approach, the
highest emitting source could be expected to achieve the floor 99 out
of 100 future tests when
[[Page 21294]]
operating under the same conditions as it did when the emissions data
were obtained. A floor that is expressed as a dioxin/furan emission
level would prevent sources from emitting at levels higher than the
(currently) worst-case source (actually, the worst-case performance
test result) currently emits. We specifically request comment on this
alternative MACT floor.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated use of an activated carbon bed (preceded by gas
reheating to above the dewpoint) as beyond-the-floor control for
dioxin/furan. Carbon beds can achieve greater than 99% reduction in
dioxin/furan emissions.\159\ We considered alternative beyond-the-floor
levels of 0.40 ng TEQ/dscm and 0.20 ng TEQ/dscm.
---------------------------------------------------------------------------
\159\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume V: Emissions Estimates and Engineering
Costs,'' March 2004, Chapter 4.
---------------------------------------------------------------------------
The incremental annualized cost of a beyond-the-floor emission
level of 0.40 ng TEQ/dscm would be $1.9 million and would provide an
incremental reduction in dioxin/furan emissions of 2.3 grams TEQ per
year, for a cost-effectiveness of $0.83 million per gram TEQ
removed.\160\ A beyond-the-floor emission level of 0.20 ng TEQ/dscm
would provide very little incremental emissions reduction--0.1 grams
TEQ per year--at additional costs. We evaluated nonair quality health
and environmental impacts and energy effects and determined that this
beyond-the-floor option would increase the amount of hazardous
wastewater generated by 210 tons per year, and would increase
electricity usage by 1.8 million kW-hours per year and natural gas
consumption by 96 trillion Btu per year.
---------------------------------------------------------------------------
\160\ Please note that, under the proposed floor level, sources
would not incur retrofit costs or achieve dioxin/furan emissions
reductions because they currently comply with the floor controls
under current RCRA regulations at 40 CFR 266.104.
---------------------------------------------------------------------------
We judge that the cost to achieve a beyond-the-floor standard of
0.40 ng TEQ/dscm is warranted given our special concern about dioxin/
furan. Dioxin/furan are some of the most toxic compounds known due to
their bioaccumulation potential and wide range of health effects,
including carcinogenesis, at exceedingly low doses. Exposure via
indirect pathways is a chief reason that Congress singled out dioxin/
furan for priority MACT control in CAA section 112(c)(6). See S. Rep.
No. 128, 101st Cong. 1st Sess. at 154-155. In addition, we note that
the beyond-the-floor emission level of 0.40 ng TEQ/dscm is consistent
with historically controlled levels under MACT for hazardous waste
incinerators and cement kilns, and Portland cement plants. See
Sec. Sec. 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). Also, EPA
has determined previously in the 1999 Hazardous Waste Combustor MACT
final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less
are necessary for the MACT standards to be considered generally
protective of human health under RCRA (using the 1985 cancer slope
factor), thereby eliminating the need for separate RCRA standards under
the authority of RCRA section 3005(c)(3) and 40 CFR 270.10(k). Finally,
we note that this decision is not inconsistent with EPA's decision not
to promulgate beyond-the-floor standards for dioxin/furan for hazardous
waste burning lightweight aggregate kilns, cement kilns, and
incinerators at cost-effectiveness values in the range of $530,000 to
$827,000 per additional gram of dioxin/furan TEQ removed. See 64 FR at
52892, 52876, and 52961. In those cases, EPA determined that
controlling dioxin/furan emissions from a level of 0.40 ng TEQ/dscm to
a beyond-the-floor level of 0.20 ng TEQ/dscm was not warranted because
dioxin/furan levels below 0.40 ng TEQ/dscm are generally considered to
be below the level of health risk concern.
For these reasons, we believe that proposing a beyond-the-floor
standard of 0.40 ng TEQ/dscm is warranted notwithstanding the nonair
quality health and environmental impacts and energy effects identified
above and costs of approximately $0.83 million per additional gram of
dioxin/furan TEQ removed. We specifically request comment on our
decision to propose this beyond-the-floor standard.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources is the same as for existing sources
under the same rationale: compliance with the carbon monoxide/
hydrocarbon emission standard and compliance with the destruction and
removal efficiency standard.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
As for existing sources, we evaluated use of an activated carbon
bed as beyond-the-floor control for new sources to achieve an emission
level of 0.40 ng TEQ/dscm. We estimate that the incremental annualized
cost for a new hydrochloric acid production furnace with average gas
flowrate to reduce dioxin/furan emissions at the floor of 0.68 ng TEQ/
dscm \161\ to achieve a beyond-the-floor emission level of 0.40 ng TEQ/
dscm would be $0.15 million. These controls would provide an
incremental reduction in dioxin/furan emissions of 0.66 grams TEQ per
year, for a cost-effectiveness of $230,000 per gram TEQ removed. We
evaluated nonair quality health and environmental impacts and energy
effects and determined that, for a new source with an average gas
flowrate, this beyond-the-floor option would increase the amount of
hazardous wastewater generated by 9 tons per year, and would increase
electricity usage by 0.14 million kW-hours per year and natural gas
consumption by 9.2 trillion Btu per year.
---------------------------------------------------------------------------
\161\ We estimate beyond-the-floor control costs assuming a new
source emits the highest levels likely under floor control based on
compliance with the carbon monoxide and destruction and removal
efficiency standards.
---------------------------------------------------------------------------
We judge that the cost to achieve a beyond-the-floor standard of
0.40 ng TEQ/dscm is warranted given our special concern about dioxin/
furan. Dioxin/furan are some of the most toxic compounds known due to
their bioaccumulation potential and wide range of health effects,
including carcinogenesis, at exceedingly low doses. Exposure via
indirect pathways is a chief reason that Congress singled our dioxin/
furan for priority MACT control in CAA section 112(c)(6). See S. Rep.
No. 128, 101st Cong. 1st Sess. at 154-155. In addition, we note that
the beyond-the-floor standard of 0.40 ng TEQ/dscm is consistent with
historically controlled levels under MACT for hazardous waste
incinerators and cement kilns, and Portland cement plants. See
Sec. Sec. 63.1203(a)(1), 63.1204(a)(1), and 63.1343(d)(3). Also, EPA
has determined previously in the 1999 Hazardous Waste Combustor MACT
final rule that dioxin/furan in the range of 0.40 ng TEQ/dscm or less
are necessary for the MACT standards to be considered generally
protective of human health under RCRA (using the 1985 cancer slope
factor), thereby eliminating the need for separate RCRA standards under
the authority of RCRA section 3005(c)(3) and 40 CFR 270.10(k).
For these reasons, we believe that proposing a beyond-the-floor
standard of 0.40 ng TEQ/dscm is warranted notwithstanding the nonair
quality health and environmental impacts and energy effects identified
above and costs of approximately $0.23 million per additional gram of
dioxin/furan TEQ removed. We specifically request comment on our
decision to propose this beyond-the-floor standard.
[[Page 21295]]
B. What Is the Rationale for the Proposed Standards for Mercury,
Semivolatile Metals, and Low Volatile Metals?
We propose to require compliance with the total chlorine standard
as a surrogate for the mercury, semivolatile metals, and low volatile
metals standards.
As discussed above, hydrochloric acid production furnaces use wet
scrubbers to remove hydrochloric acid from combustion gases to produce
the hydrochloric acid product and to minimize residual emissions of
hydrochloric acid and chlorine gas. Wet scrubbers also remove metal
HAP, including mercury, from combustion gases. To minimize
contamination of hydrochloric acid product with metals, hydrochloric
acid production furnaces generally feed hazardous waste with low levels
of metal HAP. Moreover, the wet scrubbers used to recover the
hydrochloric acid product and minimize residual emissions of
hydrochloric acid and chlorine gas also control emissions of metal HAP
to very low levels. Based on emissions testing within the range of
normal emissions (i.e., not compliance test, maximum allowed
emissions), hydrochloric acid production furnaces emit mercury at
levels from 0.1 to 0.4 [mu]g/dscm, semivolatile metals at levels from
0.1 to 4.1 [mu]g/dscm, and low volatile metals at levels from 0.1 to 43
[mu]g/dscm.162, 163
---------------------------------------------------------------------------
\162\ USEPA, ``Draft Technical Support Document for HWC MACT
Replacement Standards, Volume III: Selection of MACT Standards,''
March 2004, Chapter 2.
\163\ Except that one source emitted 330 [mu]g/dscm low volatile
metals and 0.043 gr/dscf particulate matter during compliance
testing. This source apparently detuned the acid gas absorber and
other acid gas control equipment given that it achieved less than
99% system removal efficiency for total chlorine and had total
chlorine emissions of 500 ppmv. This source would not be allowed to
operate under these conditions under today's proposed rule: 14 ppmv
total chlorine emission limit, or 99.9927 system removal efficiency.
Thus, under the proposed rule, emissions of low volatile metals and
particulate matter would be substantially lower.
---------------------------------------------------------------------------
We also note that these sources emit low levels of particulate
matter. Compliance test, maximum allowable emissions of particulate
matter range from 0.001 to 0.013 gr/dscf.
Because wet scrubbers designed to recover the hydrochloric acid
product and control residual emissions of hydrogen chloride and
chlorine gas also control emissions of mercury, and semivolatile and
low volatile metals (including nonenumerated metals), use of MACT wet
scrubbers to comply with the proposed total chlorine standard discussed
below will also ensure MACT control of metal HAP. Accordingly, we
propose to use the total chlorine standard as a surrogate for the
mercury, semivolatile metals, and low volatile metals standards.
C. What Is the Rationale for the Proposed Standards for Total Chlorine?
The proposed standards for total chlorine are 14 ppmv or 99.9927
percent total chlorine system removal efficiency (SRE) for existing
sources and 1.2 ppmv or 99.99937 percent total chlorine SRE for new
sources. A source may elect to comply with either standard.
1. What Is the Rationale for the MACT Floor for Existing Sources?
The proposed MACT floor for existing sources is compliance with
either a total chlorine emission level of 14 ppmv or a total chlorine
SRE of 99.9927 percent.
Hydrochloric acid production furnaces use wet scrubbers to remove
hydrochloric acid from combustion gases to produce the hydrochloric
acid product and to minimize residual emissions of hydrochloric acid
and chlorine gas. We have compliance test, maximum allowable total
chlorine emissions data for all 17 hydrochloric acid production
furnaces. Total chlorine emissions range from 0.4 to 500 ppmv, and
total chlorine system removal efficiencies (SRE) range from 98.967 to
99.9995 percent.
As discussed in Section VI.C above, control of the feedrate of
chlorine in hazardous waste fed to the furnace is not an appropriate
MACT emission control technique because hydrochloric acid production
furnaces are designed to produce hydrochloric acid from chlorinated
feedstocks. Consequently, the approaches we normally use to identify
the best performing sources--SRE/Feed Approach or Emissions Approach--
are not appropriate because they directly or indirectly consider
chlorine feedrate. More simply, limiting feedrate means not producing
the intended product, a result inconsistent with MACT. See 2
Legislative History at 3352 (House Report) (``MACT is not intended to *
* * drive sources to the brink of shutdown''). To avoid this concern,
we identify a floor SRE, and provide an alternative floor as a total
chlorine emission limit based on floor SRE and the highest chlorine
feedrate for any source in the data base. By using the highest chlorine
feedrate to calculate the alternative total chlorine emission limit, we
ensure that feedrate control (i.e., nonproduction of product) is not a
factor in identifying the proposed MACT floor. The alternative total
chlorine emission limit would require a source that may not be
achieving floor SRE to achieve total chlorine emission levels no
greater than the level that would be emitted by any source achieving
floor SRE.
The floor SRE is 99.9927 percent. It is calculated from the five
best SREs, and considers emissions variability. Floor SRE is an SRE
that the average of the performing sources could be expected to achieve
in 99 of 100 future tests when operating under conditions identical to
the compliance test conditions during which the emissions data were
obtained. We estimate that this SRE is being achieved by 29% of
sources.
The alternative floor emission limit is 14 ppmv, and is the
emission level that the source with the highest chlorine feedrate--
2.9E+8 [mu]g/dscm--would achieve when achieving 99.9927 percent SRE.
Approximately 24% of sources are achieving the alternative floor
levels, and these floor levels would reduce total chlorine emissions by
145 tons per year.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We evaluated improved design, operation, and maintenance of
existing scrubbers to achieve a beyond-the-floor emission level of 7
ppmv for total chlorine for existing sources, assuming a 50% reduction
in emissions from the floor level.
The national annualized compliance cost for hydrochloric acid
production furnaces to comply with this beyond-the-floor standard would
be $0.25 million, and emissions of total chlorine would be reduced by 3
tons per year. The cost-effectiveness of this beyond-the-floor standard
would be $76,000 per ton of total chlorine removed.
We evaluated nonair quality health and environmental impacts and
energy effects and determined that this beyond-the-floor option would
increase both the amount of hazardous wastewater generated and water
usage by approximately 82 million gallons per year and would increase
electricity usage by 0.34 million kW-hours per year. Generation of
nonwastewater hazardous waste would decrease by 7 tons per year.
Considering these impacts and cost-effectiveness as well, we conclude
that a beyond-the-floor standard for existing sources would not be
warranted.
For these reasons, we propose a floor total chlorine standard of 14
ppmv or 99.9927% SRE for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
The proposed MACT floor for new sources is compliance with either a
total chlorine emission level of 1.2 ppmv or
[[Page 21296]]
a total chlorine SRE of 99.99937 percent. We use the same rationale for
identifying alternative floors for new sources as discussed above in
the context of existing sources.
The new source floor SRE is the SRE that the single best performing
source (i.e, source with the best SRE) could be expected to achieve in
99 of 100 future tests when operating under conditions identical to the
compliance test conditions during which the emissions data were
obtained. The new source floor alternative emission limit is an
emission level that the source with the highest chlorine feedrate--
2.9E+8 [mu]g/dscm--would achieve when achieving 99.99937 percent SRE.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
We evaluated a beyond-the-floor standard for new sources of 0.60
ppmv based on achieving a 50 percent reduction in emissions by
improving the design/operation/maintenance of the wet scrubber. The
incremental annualized cost for a new solid fuel-fired boiler with
average gas flowrate to meet a beyond-the-floor level of 0.60 ppmv
would be approximately $0.15 million and would provide an incremental
reduction in total chlorine emissions of 0.07 tons per year, for a
cost-effectiveness of $2.1 million per ton of total chlorine removed.
We evaluated nonair quality health and environmental impacts and
energy effects and determined that, for a new source with average gas
flowrate, this beyond-the-floor option would increase both the amount
of hazardous wastewater generated and water usage by approximately 26
million gallons per year and would increase electricity usage by 0.25
million kW-hours per year. Considering these impacts and cost-
effectiveness as well, we conclude that a beyond-the-floor standard for
new sources would not be warranted.
For the reasons discussed above, we propose a total chlorine
standard of 1.2 ppmv or a total chlorine SRE of 99.99937 percent for
new sources.
D. What Is the Rationale for the Proposed Standards for Carbon Monoxide
or Hydrocarbons?
To control emissions of organic HAP, existing and new sources would
be required to comply with either a carbon monoxide standard of 100
ppmv or a hydrocarbon standard of 10 ppmv.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Hydrochloric acid production furnaces that burn hazardous waste are
currently subject to RCRA standards that require compliance with either
a carbon monoxide standard of 100 ppmv, or a hydrocarbon standard of 20
ppmv. Compliance is based on an hourly rolling average as measured with
a CEMS. See Sec. 266.104(a). All hydrochloric acid production furnaces
have elected to comply with the 100 ppmv carbon monoxide standard. We
propose floor standards of 100 ppmv for carbon monoxide or 10 ppmv for
hydrocarbons for the same reasons discussed above in the context of
liquid fuel-fired boilers.
There would be no incremental emission reductions associated with
these floors because sources are currently achieving the carbon
monoxide standard.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
Our considerations for beyond-the-floor standards for existing
hydrochloric acid production furnaces are identical to those discussed
above for existing liquid fuel-fired boilers. For the reasons discussed
above in the context of liquid fuel-fired boilers, we conclude that
beyond-the-floor standards for carbon monoxide and hydrocarbons for
existing hydrochloric acid production furnaces are not warranted.
3. What Is the Rationale for the MACT Floor for New Sources?
MACT floor for new sources would be the same as the floor for
existing sources--100 ppmv for carbon monoxide and 10 ppmv for
hydrocarbons--and based on the same rationale.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
Our considerations for beyond-the-floor standards for new
hydrochloric acid production furnaces are identical to those discussed
above for new liquid fuel-fired boilers. For the reasons discussed
above in the context of liquid fuel-fired boilers, we conclude that
beyond-the-floor standards for carbon monoxide and hydrocarbons for new
hydrochloric acid production furnaces are not warranted.
E. What Is the Rationale for the Proposed Standard for Destruction and
Removal Efficiency?
To control emissions of organic HAP, existing and new sources would
be required to comply with a destruction and removal efficiency (DRE)
of 99.99% for organic HAP. For sources burning hazardous wastes F020,
F021, F022, F023, F026, or F027, however, the DRE standard is 99.9999%
for organic HAP.
1. What Is the Rationale for the MACT Floor for Existing Sources?
Hydrochloric acid production furnaces that burn hazardous waste are
currently subject to RCRA DRE standards that require 99.99% destruction
of designated principal organic hazardous constituents (POHCs). For
sources that burn hazardous wastes F020, F021, F022, F023, F026, or
F027, however, the DRE standard is 99.9999% destruction of designated
POHCs. See Sec. 266.104(a).
The DRE standard helps ensure that a combustor is operating under
good combustion practices and thus minimizing emissions of organic HAP.
Under the MACT compliance regime, sources would designate POHCs that
are organic HAPs or that are surrogates for organic HAPs.
We propose to establish the RCRA DRE standard as the floor for
existing sources because it is a currently enforceable Federal
standard. There would be no incremental emission reductions associated
with this floor because sources are currently complying with the
standard.
2. EPA's Evaluation of Beyond-the-Floor Standards for Existing Sources
We considered a beyond-the-floor level for DRE based on use of
better combustion practices but conclude that it may not be replicable
by the best performing sources nor duplicable by other sources given
that we cannot quantify better combustion practices. Moreover, we
cannot ensure that a higher DRE standard would significantly reduce
emissions of organic HAP given that DRE measures the destruction of
organic HAP present in the boiler feed rather than gross emissions of
organic HAP. Although a source's combustion practices may be adequate
to destroy particular organic HAP in the feed, other organic HAP may be
emitted as products of incomplete combustion.
For these reasons, and after considering nonair quality health and
environmental impacts and energy requirements, we are not proposing a
beyond-the-floor DRE standard for existing sources.
3. What Is the Rationale for the MACT Floor for New Sources?
We propose to establish the RCRA DRE standard as the floor for new
sources because it is a currently enforceable Federal standard.
4. EPA's Evaluation of Beyond-the-Floor Standards for New Sources
Using the same rationale as we used to consider a beyond-the-floor
DRE
[[Continued on page 21297]]
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