FS-FPL-4710

Fiber Loading for Lightweight High-Opacity Papers

Introduction

The shift to alkaline conditions in papermaking has been prompted in part by the increased level of filler permitted in alkaline-sized papers. Because alkaline sizing enhances paper strength, a higher level of filler can be incorporated into the sheet. Calcium carbonate, a filler that could not be used in acid sized papers, is popular as a filler in alkaline-sized papers because of its high brightness level [1,2]. In general, fillers cost less than fiber, and have the ability to improve the surface smoothness, optical and printing properties, and the formation of paper. However, as the level of filler increases, the interfiber bonding decreases. If additional filler could be added inside pulp fibers, interfiber bonding might be maintained.

A method to incorporate fillers inside fibers has been the subject of extensive research. Scallan and associates [3,4] reported the first studies as lumen loading. These experiments focused on the use of titanium dioxide. An excess of titanium dioxide was mechanically mixed with a pulp slurry depositing titanium dioxide within the fiber lumen. However, limitations of this method were the large excess of titanium dioxide required for lumen loading and the need of a separate process for recycling the excess filler.

More recent studies on cell wall loading have been reported by Allan and associates [5]. Their approach was to saturate pulp fibers with sodium carbonate and react the resulting pulp mixture with salt-containing calcium (e.g., calcium chloride). The resulting pulp mixture could contain high levels of calcium carbonate within the fiber; however, additional processing was required to remove the salt remaining in the mixture.

Fiber loading, which was developed at the Forest Products Laboratory (FPL), consists of at least two steps [6]. First, calcium hydroxide is mixed into a pulp fibers slurry. Then, the pulp and calcium hydroxide mixture is reacted using a high consistency pressurized reactor (refiner or disk disperser) under carbon dioxide pressure to precipitate calcium carbonate. Calcium carbonate is deposited within, on the surface of, and outside the pulp fibers, and is termed fiber loaded precipitated calcium carbonate (FLPCC). As a result of fiber loading, fiber bonding is increased as shown by increased handsheet strengths.

Fiber-loaded pulps are stronger than similar direct-loaded pulps at the same precipitated calcium carbonate (PCC) levels as a result of three independent mechanisms: (a) deposit of FLPCC within the fiber wall and lumen [6], (b) gentle refining of fiber at high pH [7], and (c) gentle refining of fiber at high consistency [7,8]. The low energy (approximately 6.84 x 104 kJ/metric ton) needed for the reaction process during fiber loading causes only small drops in pulp Canadian standard freeness (CSF) (30 to 40 ml) [7,9]. Measurement of fiber length, kink, curl, and fines (fibers <0.2 mm) content after fiber loading revealed no change in fiber characteristics [10]. By enhancing fiber bonding without any significant loss in freeness, fiber loading is thus a viable method to produce lightweight high-opacity paper.

The morphology and particle size of the FLPCC particle is critical. Calcium carbonate is known to exist in three distinct crystal structures. The structure most important to papermakers is calcite, which itself has over 300 reported forms [11]. The properties of these crystals, such as shape, surface area, and size distribution, determine the fiber/filler interactions and ultimately influence the strength, optical, and printing properties of the final paper product. The fiber loading process environment has a profound impact on properties of the FLPCC crystals.

As grammages are reduced, the printing inks tend to penetrate through the paper (strike-through) and can be a limiting factor in grammage reduction. At reduced grammages, filler properties profoundly effect strike-through. How FLPCC particles effect strike-through is unknown and difficult to predict. Newsprint and white-top liner grades need to reduce grammage, improve printability, or both in order to remain viable [12].

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Initial Experiments

Initially, fiber-loading experiments at the FPL were directed at minimizing a critical problem of recycling-hornification. If fillers could be precipitated within fiber voids, collapse of these voids during subsequent drying might be reduced. Although the impact of fiber loading on hornification remains unclear, other economic and environmental benefits were apparent.

In our initial study [13], we investigated whether complete conversion of the reactants had occurred (using x-ray diffraction), where calcium carbonate was deposited (scanning electron microscopy (SEM) analysis), and how the properties of handsheets prepared from fiber-loaded pulps compared to those made from direct-loaded pulps (conventional method of adding filler in the doler tank or papermachine chest).

The SEM revealed the presence of calcium carbonate crystals on both external surfaces and within the cell lumen; x-ray microprobe analysis identified the presence of calcium within the cell wall. Calcium carbonate was readily detected and identified with SEM and x-ray micro-analytical methods. X-ray diffraction measurements were made to confirm to the presence of crystalline calcium carbonate precipitate after the reaction in a pressurized refiner. For comparison, two diffraction traces were presented. A trace from a fiber-loaded handsheet prepared from unbleached softwood fiber (loaded with calcium hydroxide and treated with CO2 in the refiner). A similar trace was obtained from a commercial PCC suspension, deposited and dried on a filter paper. Comparison of the x-ray diffraction traces indicated that the patterns were identical, and the crystals can be indexed as the rhombohedral form of calcium carbonate.

Initial fiber loading experiments indicated that rhombohedral calcite crystals in the 1 to 3 um range were achievable. Cross-sections of fiber-loaded softwood pulp and handsheet fibers examined by SEM showed that calcium carbonate was precipitated in discrete angular particles, i.e., crystals. Crystalline aggregates could be seen in the lumen and on the fiber surfaces (Figures 1,2). The distinctive spectrum of calcium was found by x-ray microanalysis on the surface, in the lumen, and in the wall [13]. This information indicates that a portion of the calcium ions diffuse into the fiber wall and subsequently react with carbon dioxide depositing calcium carbonate. Figure 3 confirms the presence of calcium carbonate on both the internal and external surfaces of pulp and handsheet fibers.

Investigations of fiber loading on never-dried, bleached hardwood pulp are summarized in Figures 4-7. These figures compare strength, optical properties, and density to paper ash levels on handsheets made from direct and fiber-loaded pulps. In each case, a dotted line indicated interpolated values for direct-loaded handsheets, at Canadian standard freeness (CSF) values comparable to fiber-loaded pulps at the same ash level.

For strength properties, the curve for fiber-loaded handsheets gives higher strength values at the same ash levels as the direct-loaded handsheets at the same CSF values. This is partly due to the difference in consistency at which the refining takes place. The direct-loaded pulps were disk refined at low consistency, while the fiber-loaded pulp was pressurized refined at high consistency. In general, high-consistency refining is known to have beneficial effects on strength properties [14]. However, we compared our fiber loading method with direct loading at low consistency because that is the consistency conventionally used for commercial production.

Figure 4 illustrates that at any given burst index, fiber-loaded handsheets contain 3.5% to 4.0% more calcium carbonate than do handsheets made from direct-loaded pulp. For example, the carbonate content of a handsheet can be increased from 7.5% to about 11.5% with the same burst index. Fiber loading exhibits even greater advantage over direct-loading when comparing tear indices of handsheets prepared from the two processes. To achieve comparable tear strength as the 7.5% carbonate handsheet, 15.5% carbonate can be incorporated by fiber-loading method, an increase of 8 percentage points (Figure 5).

Scattering coefficient of the two loading methods are shown Figure 6. This figure shows that scattering coefficient values for 7.5% ash on direct-loaded handsheets compare with 11.5% ash content on the fiber-loaded handsheets. Fiber loading gave comparable scattering coefficient properties at 4% higher carbonate content.

At equal ash content levels, fiber-loaded handsheets exhibit poorer optical properties in comparison to direct-loaded sheets. This is understandable because the papermaker calcium carbonate was specifically designed in terms of crystal morphology and particle size to achieve maximum scattering power. In addition, filler in close contact with cell wall material (e.g., inside cell lumen) may inherently scatter less, because the difference in refractive index between filler and fiber material is smaller than that between filler and air.

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Figure 3. Handsheet density of fiber-loaded pulp is compared to direct-loaded handsheet density in Figure 7. Fiber-loaded handsheets are shown to be 60kg/m3 more dense than the 7.5% ash direct-loaded handsheets.

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Figure 4. Comparison between direct and fiber loading on BL. HW 430 or 330 CSF.

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Figure 5. Comparison between direct and fiber loading on BL. HW 430 or 330 CSF.

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Figure 6. Comparison between direct and fiber loading on BL. HW 430 or 330 CSF.

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Figure 7. Comparison between direct and fiber loading on BL. HW 430 or 330 CSF.

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In a subsequent study [10] we investigated the impact of high consistency and high pH processing on fiber properties and evaluated the parameters that influence the dimensional stability of handsheets made with pulp obtained from recycled fiber. The effects of high consistency hot dispersion followed by conventional high consistency fiber loading were compared with a control employing low consistency fiberization and minimal mechanical processing. Three differently processed samples of this pulp were compared. Although fiber loading increased individual fiber curl slightly more than that of the other two processing methods, most curl indices obtained were within the range considered to be relatively straight. We found a direct correlation between the coefficients of hygroexpansion and the curl indices of pulps reprocessed by the high consistency methods. Fiber loaded handsheets displayed slightly higher hygroexpansion than did direct-loaded sheets at comparable ash levels. Fiber length, kink, curl, and fines (fibers <0.2 mm) content after fiber loading revealed essentially no change in fiber characteristics. The improved water retention values obtained with recycled fiber-loaded pulp is consistent with improved water removal of fiber loaded pulp which was indicated both by increased freeness after loading and higher solids after pressing when compared with conventionally filled handsheets. Improved water removal could translate to faster drying, energy savings, or both on the papermachine.

Industrial Evaluations

There have been two published evaluations of fiber loading. The first evaluation [15] involved fiber loading virgin never -dried birch hardwood bleached kraft pulp. An atmospheric high consistency refiner was used as a mixer for adding calcium hydroxide to high consistency pulp, followed by high consistency pressurized refining under carbon dioxide pressure for the reaction stage. The fiber-loaded pulp was then processed on a pilot scale paper machine. The paper machine trials revealed some technical obstacles. Changes in color and brightness, cross machine web shrinkage, and apparent density increases were observed and became the focus of the follow-up laboratory evaluations following the trials. The problems were duplicated in the laboratory, and methods for preventing or over-coming the obstacles were developed.

Brightness and yellowing that occurred in the pilot papermachine trials were traced to residual lignin in the totally chlorine free (TCF) bleached pulp. We demonstrated that including a low level of hydrogen peroxide prevented brightness loss and yellowing of the fiber-loaded pulp. Web shrinkage was tracked to greatly improved water removal for fiber loaded pulps compared to the conventional. Web shrinkage occurred before the paper machine cross machine direction restraint rolls. This was due to improved water removal. Filler retention was shown not to be a problem with fiber loaded pulps. Apparent density was increased by about 10% for fiber loaded pulps. Laboratory hand sheet experiments demonstrated several methods for bulking the sheet, e.g., increased use of thermomechanical (TMP) pulp and decreased wet pressing.

The second published industrial evaluation of fiber-loading involved deinked mixed office waste (MOW)[9]. A disk disperser was used to convert calcium hydroxide to calcium carbonate on the deinked pulp. Conventional deinking mill conditions were simulated, including typical pulping chemistry, deinking process sequence, and process water clarification and recirculation. Industrial-scale fiber loading was technically successful; calcium carbonate was completely converted to calcium carbonate and deposited on the external and internal surfaces of pulp fibers. However, we found that calcium hydroxide had to be thoroughly mixed with fiber prior to reaction with carbon dioxide to insure the uniform loading and complete conversion to carbonate. The fiber loading processes used in the trials needed to be modified to obtain optimum conversion to calcium carbonate. Separate operations for mixing calcium hydroxide into the pulp and chemical reaction with carbon dioxide were needed.

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Rationale

Deinking Sludge Reduction

Because the PCC in printing papers generates tons of deinking sludge which become a disposal problem, we explored the impact fiber-loading could have on the calcium carbonate portion of sludge production during recycling of recovered paper [16]. Once calcium carbonate is precipitated in the fiber interior and on the fiber surfaces, much of the carbonate remains with the fiber when recycled. We compared the retention of FLPCC with the conventional papermaking process that adds PCC to recycled pulp. Hot dispersion, frequently one of the last steps in recycling pulp, breaks down and distributes residual contaminants. Hot dispersion followed by direct loading of PCC (we designated these two steps as direct loading for this study) is a common final step in deinking wastepaper derived pulps. Both direct loading and fiber loading process high consistency pulp using a high consistency refiner. The fiber-loading process operates at ambient temperature; the direct-loading process dispersion operates at elevated temperatures. However, our preliminary experiments suggest that the fiber-loading process results in at least as good dispersion as the direct loading process [17]. So, fiber loading could possibly replace direct loading using the same high consistency refiners already in place in some papermills. In this study, a common never-dried pulp filled by both processes was recycled several times to evaluate relative impact on whitewater and, ultimately, sludge production. The direct-loading and fiber-loading processes were compared with a control pulp to which calcium carbonate was added, directly followed by drying and recycled by fiberizing without additional mechanical treatment.

The following results were obtained from the retention study: Handsheet physical and optical properties of recycled fiber-loaded pulps were maintained without need for additional refining or carbonate addition. Measuring recycled handsheet ash levels for fiber-loaded pulps required only about 50% of the calcium carbonate addition as that for direct-loaded pulps. Recycled fiber-loaded pulps tended to have shorter fiber length than the direct loaded pulps, indicating perhaps natural fines retention for fiber loading. Process water analysis showed about 50% less total suspended solids and 50% less calcium ion concentration than did the direct-loaded pulps, indicating about 50% less calcium carbonate in the fiber-loaded process water. Cellulose fines and COD analysis showed somewhat less cellulose fines in the fiber loading process water than for the direct-loaded pulps. Fiber-loading shows potential to reduce calcium carbonate filler content of deinking sludge by up to 50%.

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Economics and Energy

According to a recent feature article on paper industry needs, "research on breakthrough technology that significantly increases the capital effectiveness of paper machines and papermaking should rank among the highest pulp and paper industry research priorities"[18]. We believe that fiber loading can be a key factor in producing lightweight high-opacity newsprint at an attractive return on investment (ROI).
Newspaper publishers are well aware of the economic benefits of lightweight newsprint: As stated in a recent newsletter, "Over the past decade newspapers on the West Coast have shifted to lighter grammage newsprint as producers have pushed to save on fiber costs…Today, West Coast publishers and producers are looking at reducing grammages further to 43 g/m2 newsprint, in line with a trend catching on in Europe and Asia" [18].

We investigated the ROI for fiber loading for a hypothetical newsprint mill [19]. The investment analysis covered savings resulting from reduced fiber needs, substitution of low-cost FLPCC for higher cost fiber, and reduced drying costs, as well as a premium for lightweight paper. We balanced these savings with the added capital costs for new equipment, energy needed to operate the new process, additional personnel, depreciation, maintenance, and bleaching chemical costs.

The assumptions and estimated costs associated with a hypothetical newsprint mill producing 600 metric tons of newsprint/day, operating 350 days/year are shown in Table I. The mill is assumed to use a mix of 80% softwood thermomechanical pulp (TMP) and 20% deinked pulp (DIP). The fiber-loading process consists of four major operations: fiber fractionation, dewatering of long fiber fraction, mixing of bleach chemicals and calcium hydroxide into pulp, and reacting of pulp with carbon dioxide in high-consistency pressurized reactor (refiner).

We assumed that the 600 daily metric tons are fractionated into equal amounts (300 tons) of long and short fibers. Only the 300 tons/day of long fiber are processed through the fiber-loading equipment. The additional cost for purchasing and installing the equipment is estimated at $4.396 million. An additional 25% of installed cost for engineering and soft expenses comes to $1.934 million, for a total capital cost of $6.333 million. Depreciation of total installed cost was calculated on a 10-year straight-line basis as $439,650/year. The cost of additional personnel was estimated at $50,000/year. Energy for operating the fiber loading equipment was estimated at 2.4 x 1010 kJ/year. We also included a $65,946/year maintenance fund of 1.5% of the installed cost.

Savings which would result from reduction in grammage and increased FLPCC content were calculated assuming the cost of FLPCC at both $75 and $150/metric ton. The cost of FLPCC varies depending on the availability of carbon dioxide and calcium hydroxide at the mill site. We did not attempt to estimate the impact of the many factors involved in the FLPCC raw material costs, and merely used a cost at both the high and low ends. The estimated savings per year for reduced grammage and increased FLPCC content included the additional cost of hydrogen peroxide bleaching chemicals. Additional bleaching chemicals are needed to prevent alkaline darkening when alkaline calcium hydroxide is added to lignin-containing mechanical pulps. We assumed a cost of $0.66/kg for hydrogen peroxide, $0.37/kg for magnesium sulfate, and $0.22/kg for sodium silicate.
Premium for reduced grammage paper $2.24/metric ton/g grammage

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Savings resulting from reduced drying were also estimated. For the reduced grammage, values were obtained by multiplying a ratio of the grammage at the lower level to grammage at the original level (assumed to be 49 g/m2) by energy needed for drying paper (Table I) [20]. The energy was then converted to a dollar value by using the heating value and cost of natural gas. The beneficial effect of FLPCC in increasing solids content prior to drying has been determined experimentally and published [17,21]. We multiplied the drying energy needed for drying pulp by a factor proportional to the fiber fraction of the total solids.

As noted in Table I, fiber in the mill was valued at $242/metric ton [20]. Manufacturers of lightweight newsprint have claimed a premium in the tonnage price. Price differentials of $45 to $65/metric ton have been reported for reducing grammage from 48.8 to 43.9 g/m2 [22]. Another source reports that 45 g/m2 newsprint costs 6% more per metric ton than its 48.8-g/m2 counterpart, but yields an additional 8% of printable surface [12]. However, the newsprint grades with reduced grammage probably do not have increased strength and opacity coupled with high Canadian standard freeness, which are possible with fiber-loaded newsprint. Rather, the premium for lightweight newsprint is probably for the additional cost of bleached softwood kraft pulp required for reducing grammage. Our calculations for savings include only 20% of the reported average lightweight premium. That is, we added a premium of $2.24/metric ton for each gram reduced. This is a conservative estimate and tends to underestimate the value of fiber loading to the paper manufacturer. Also, we did not include a value for reduced shipping charges, which could be a considerable added value for overseas shipments.

Our ROI calculations were based on total savings divided by total capital costs. Savings included reduced drying, filler for fiber substitution, and premium for reduced grammage. From these savings we subtracted costs for additional personnel, running the process, depreciation, and maintenance.

Figures 8 and 9 show estimated yearly cost savings for reduced fiber and increased FLPCC use. We obtained savings for both the reduced grammage and increased FLPCC content, but the reduced grammage had the greatest impact on savings. As shown in Figure 8, only the additional 8% FLPCC approached a positive value, assuming that FLPCC costs $75/metric ton and grammage is not reduced. If FLPCC is assumed to cost $150/metric ton, fiber reduction of about 2 g/m2 is needed to obtain savings (Figure 9).

Savings resulting from reduced drying are listed in Table II. We report the savings as kilojoules per year and the corresponding dollar value. This is based on our assumption that substituting FLPCC for fiber will result in proportionately higher solids that enter the dryer section of the paper machine. The savings range from $73,540/year for 2 g/m2 fiber reduction and 4% increase in FLPCC to $178,923/year for 6 g/m2 fiber reduction and 8% increase in FLPCC.

The reported rate of return on capital investment includes the cost of bleaching chemicals at both 1% and 0.5% hydrogen peroxide levels (Tables III and IV). The amount of bleaching chemicals to be added to the fiber loading process depends on many factors [8]. For example, the pulp for fiber loading may have been highly bleached and only sufficient chemicals to prevent alkaline darkening are required to obtain relatively low brightness newsprint. Another possibility is that value-added newsprint grades may require especially high brightness and so a high level of hydrogen peroxide is needed to obtain the additional brightness. Therefore, we calculated ROIs at both the 1% and 0.5% hydrogen peroxide levels. For both levels, we obtained positive ROIs for all levels of grammage reduction and FLPCC increase.

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Figure 9. Annual savings from reducing fiber and increasing FLPCC assuming FLPCC costs $150/ton.

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Assuming that a reduction of 4 g/m2 and an additional 6% of FLPCC are reasonable goals for fiber-loaded newsprint, high ROIs can be reached. Assuming that FLPCC is available at $150/metric ton, the ROI is estimated to be 59.7%; at $75/metric ton FLPCC, the ROI is estimated to be 73.4%. If only 0.5% hydrogen peroxide is used with typical stabilizing chemicals, the corresponding ROIs are further improved. At $150/metric ton FLPCC, fiber reduction of 4 g/m2, and FLPCC increase of 6%, the ROI is 81.9% and 96.5% at $75/metric ton FLPCC. These ROIs are significantly higher than the typically reported ROIs of 5% to 10% for papermaking capital investments [18].

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Our engineering analysis for estimating cost reduction is based on producing lightweight high-opacity newsprint by fiber loading. Similar applications of fiber loading are possible for mottled and white-top linerboard and printing & writing grades. We have not included the engineering analysis of how the faster paper machine speeds used to produce lightweight high-opacity paper increase the rate of production. Nor have we included the benefits of reduced greenhouse gas emissions [23], reduced process water solids that result from improved FLPCC retention [16], and pacification of pitch and stickies [17], all of which accompany fiber loading. Nor have we investigated the effect of improved printing surface that is potentially possible with partially filled fibers and increased levels of FLPCC achieved with fiber loading. All of these advantages of fiber loading have an associated economic value that can be estimated and all are potential topics for future engineering analyses.

Greenhouse Gas Emission Reduction

In order to estimate the potential reduction in greenhouse gas emissions from all U.S. newsprint mills converting over to production of lightweight high-opacity newsprint, we determined first the greenhouse gas emission reductions for a single hypothetical newsprint mill. The analysis consisted of calculating the reduction of CO2, N2O, and CH4 emissions for various levels of grammage reduction and increased FLPCC levels possible with fiber loading. The calculations covered the savings in drying both from reduced fiber needs and for increased FLPCC levels, and reduced energy needed for processing pulp. This was balanced by the increased energy needs for operating the fiber loading processing equipment.

The same process assumptions and estimated energy uses, which effect the associated greenhouse gas emissions, were again made for a hypothetical newsprint mill producing 600 metric tons of newsprint per day as was used for the economic and energy evaluations [19].

Drying energy savings for reduced grammage were obtained by multiplying the a ratio of grammage at the lower level to grammage at the original level (assumed to be 49 g/m2) by the energy needed for drying paper (1.98 x106 kJ/metric ton)[20]. The energy source for drying was assumed to be natural gas. The reduction of greenhouse gases due to a reduction in natural gas use were calculated on the basis of: 50.7 metric tons of CO2 /109 kJ, 3.5x10-3 metric tons of N2O /106 kJ, and 1.29x10-3 metric tons of CH4 /106 kJ of natural gas [24].

The beneficial effect of FLPCC in increasing solids content prior to drying has been determined experimentally and published [17,21]. Thus, we multiplied the drying energy needed for drying pulp by a factor proportional to the fiber fraction of the solids.

The energy needed for processing the pulps was estimated at 1.8x106 kJ/metric ton for DIP and 10.1x106 kJ/metric ton for TMP [20]. Energy for processing pulps was assumed to be electricity from bituminous coal. The reduction of greenhouse gases from a reduction in the use of coal were calculated on a basis of 88.4 metric tons of CO2 /109 kJ, 3.0x10-3 metric tons N2O /109 kJ, and 2.0x10-3 metric tons CH4 /109 kJ of coal [24]. The reduction of greenhouse gases due to a reduction in coal use were calculated by the percent energy saved times the energy needed for processing pulps times the appropriate greenhouse gas factor for the energy saved.

Reductions in energy and greenhouse gas emissions were balanced by the energy needed for operating the fiber loading equipment. The energy for operating the fiber loading equipment was estimated at 2.4x1010 kJ/year [19]. Figures 10-12 show the reduction of green house gas emissions due to the reduction in grammage and increase in FLPCC possible for various scenarios. The greenhouse gases reported are carbon dioxide, nitrous oxide, and methane. The greatest greenhouse gas reduction is for CO2 (Figure 10). Increasing the FLPCC levels with fiber loading is more effective for reducing CO2 emissions than reducing grammage.

In Figure 11 we also see a similar pattern for N2O emissions as for the previous CO2 pattern. The level of FLPCC has a greater effect on N2O emissions than grammage reduction and results in about three orders of magnitude smaller than for CO2 emissions. The emissions for methane type gases from reduction in grammage and increases in FLPCC are an order of magnitude lower than for the N2O type gases (Figure 12).

Using the above estimates for a single newsprint mill, we estimated the potential reductions in greenhouse gas emissions for the entire U.S. The U.S. production of newsprint is about 6.5x106 metric tons per year [22]. Assuming that a reasonable goal for lightweight high opacity newsprint by fiber loading is for a reduction in grammage of 4g/m2, and an increase of as by 6% FLPCC, the following estimates can be made: 341,000 metric tons/year of CO2, 127.1 metric tons/year of N2O, and 8.7 metric tons /year of CH4 can be reduced from present newsprint manufacture in the U.S.

The main use of energy in newsprint manufacturing is in the drying process [20,25]. Even the small percentage reduction (10-20% potential reduction in drying energy needs)[19], possible by producing lightweight high-opacity newsprint, still significantly reduces greenhouse gas emissions in terms of absolute numbers.

Adopting fiber loading for domestic production of lightweight high-opacity newsprint for current newsprint production has the potential for reducing CO2 emissions by over 340,000 metric tons per year, as well as over 120 metric tons of N2O and 8 metric tons of CH4. Given the high reductions in greenhouse gases possible by lightweight high-opacity newsprint, the environmental benefits for producing lightweight high-opacity mottled and white-top linerboard and printing & writing grades need to be assessed.

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Figure 10. Annual reduction in CO₂ emission from reducing grammage and increasing FLPCC.

Figure 12. Annual reduction in CH4 emissions from reducing grammage and increasing FLPCC.

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REFERENCES

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For more information contact the author Mr. John Klungness.

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