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Emissions of Greenhouse Gases Report
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High-GWP Gases
Total Emissions | Hydrofluorocarbons | Perfluorocarbons | Sulfur Hexafluoride |
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Total Emissions |
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Greenhouse gases with high global warming potential (high-GWP gases) are
hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride
(SF6), which together represented 2.5 percent of U.S. greenhouse gas emissions
in 2008. |
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Emissions estimates for the high-GWP gases are provided to EIA by the EPAs
Office of Air and Radiation. The estimates are derived from the EPA Vintaging
Model. |
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For this years EIA inventory, 2007 values for PFCs and SF6 are used as
placeholders. The updated values will be available when the U.S. inventory
is submitted to the UNFCCC in April 2010. |
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Emissions of high-GWP gases have increased steadily since 1990 (Figure
25 on right and Table 26 below), largely because HFCs are being used to replace chlorofluorocarbons
(CFCs), hydrochlorofluorocarbons (HCFCs), and other ozone-depleting substances
that are being phased out under the terms of the Montreal Protocol, which
entered into force on January 1, 1989. |
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PFC emissions have declined since 1990 as a result of production declines
in the U.S. aluminum industry as well as industry efforts to lower emissions
per unit of output. |
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Emissions of other HFCs, which are aggregated to protect confidential
data, have been updated for 2008, showing a 4.4-percent increase from 2007. |
Data for all years 1990-2008
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figure data
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Hydrofluorocarbons |
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HFCs are compounds that contain carbon, hydrogen, and fluorine. Although
they do not destroy stratospheric ozone, they are powerful greenhouse gases.
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HFCs are used as solvents, residential and commercial refrigerants, firefighting
agents, and propellants for aerosols. |
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Emissions of substitutes for ozone-depleting substances, including HFC-32,
HFC-125, HFC-134a, HFC-143a, and HFC-236fa, have grown from trace amounts
in 1990 to nearly 121 MMTCO2e in 2008 (Table 27 below). |
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Nearly 90 percent of the growth in HFC emissions since 1990 can be attributed
to the use of HFCs as replacements for ozone-depleting substances. The
market is expanding, with HFCs used in fire protection applications to
replace Halon 1301 and Halon 1211. |
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Since 2000, HFC-134aused as a replacement for CFCs in air conditioners
for passenger vehicles, trains, and buseshas accounted for the largest
share of HFC emissions (Figure 26 on right). |
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Under the Clean Air Act, manufacture and import of HCFC-22, except for use
as a feedstock and in equipment manufacture before 2010, are scheduled
to be phased out by January 1, 2010. Manufacturers of HCFC-22 are using
cost-effective methods to make voluntary reductions in the amount of HFC-23
that is created as a byproduct of HCFC-22 manufacture; however, HCFC-22
production remains a large and steady source of U.S. emissions of HFC-23. |
Data for all years 1990-2008
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Perfluorocarbons |
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The two principal sources of PFC emissions are domestic aluminum production
and semiconductor manufacture, which yield perfluoromethane (CF4) and perfluoroethane
(C2F6) (Figure 27 on right and Table 28 below). |
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While PFC emissions from aluminum production have declined markedly since
1990, the decline has been offset in part by increased emissions from semiconductor
manufacturing. |
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Emissions from process inefficiencies during aluminum production (known
as anode effects) have been greatly reduced; in addition, high costs
for alumina and energy have led to production cutbacks. |
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Perfluoroethane is used as an etchant and cleaning agent in semiconductor
manufacturing. The portion of the gas that does not react with the materials
is emitted to the atmosphere. |
Data for all years 1990-2008
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figure data
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Sulfur Hexafluoride |
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SF6, an excellent dielectric gas for high-voltage applications, is used
primarily in electrical applicationsas an insulator and arc interrupter
for circuit breakers, switch gear, and other equipment in electricity transmission
and distribution systems. |
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Industry efforts to reduce emissions of SF6 from electrical power systems
have led to a decline in emissions since 1990 (Figure 28 on right and Table 29 below). |
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SF6 is also used in magnesium metal casting, as a cover gas during magnesium
production, and as an atmospheric tracer for experimental purposes. |
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Other, minor applications of SF6 include leak detection and the manufacture
of loudspeakers and lasers. |
Data for all years 1990-2008
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figure data
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