The Pulp and Paper Industry
The U.S. paper industry leads the world with over 24 percent of global paper production capacity (American Forest and Paper Association, 1998a). It produces 9 million tons of pulp each year (United States Environmental Protection Agency, 1997a). The pulp and paper industry is the most capital intensive in the United States, spending approximately $130,000 per employee each year in plant and equipment. Economies of scale thus are critical to profitability. Pulp and paper mills produce up to 5,000 tons of paper per day to satisfy a national consumption rate of 700 pounds per American per year, double the consumption in 19601 (Blum et al., 1997).
Paper and paperboard products are made from pulp. Pulp is made predominately from wood, but in many cases it is made from other plant fibers such as cotton, linen, and hemp and grasses such as straw, wheat, and kenaf. More recently, recycled paper has become a common material input. In 1996, American paper mills recovered 44.8 percent of postconsumer U.S. paper, and the industry has set a 50 percent paper recovery goal by the year 2000 (American Forest and Paper Association, 1998b).
The industry is relatively well integrated, with some companies managing almost every aspect of the paper cycle: fiber production in forests, pulping, paper
making, and paper recycling. In assessing the pulp and paper sector, the committee elected to examine the entire life cycle of the industry (Figure 7-1).
About 3.5 billion cubic meters of wood is harvested worldwide each year (Food and Agriculture Organization, 1995), of which 500 million cubic meters (or 14 percent) is used for pulp and paper, 31 percent for fuel wood, and the rest for solid wood. Data for 1993 indicate that about 650 million cubic meters of wood entered the U.S. economy. Seventy-eight percent was from trees, 10 percent from recycling, and 12 percent from imports. As Figure 7-2 shows, 26 percent was consumed as solid wood, 26 percent as paper, and 36 percent as fuel; 10 percent was exported.
While natural forests are the primary source of pulp wood and solid wood, the global trend is toward acquiring wood grown on plantations or intensively managed natural regeneration forests that resemble plantations. Survey findings on the sources of wood fiber for the global paper industry reveal that 66 percent was from managed natural regeneration forests and plantations, 17 percent from unmanaged regeneration forests, and the rest from virgin sources (Grieg-Gran et al., 1997).
Pulp and Paper Production
Figure 7-3 shows the production of paper from wood pulp. Logs are first debarked. Stripped bark is then used for fuel or to enrich soil. Wood can be broken down into fibers by mechanical or chemical methods. In the mechanical process, wood fiber is physically separated from the wood by forcing debarked logs and hot water between enormous rotating steel discs with teeth that tear the wood apart or by pressing the logs against grindstones. The mechanical pulping process uses considerable amounts of electricity (2,000 kWh/ton of pulp) but has a high yield (about 90 percent). The wood requirements for mechanical pulping are less than in chemical pulping. Most of the electrical energy that goes into the refiner is liberated as steam, which is subsequently used to dry the paper. Mechanical pulp mills use about 8,000 gallons of water per ton of pulp produced. Bleaching of mechanical pulps is done with hydrogen peroxide or sodium hydrosulfite. Mechanical pulp constitutes about 10 percent of the pulp made in the United States. Recent technology has permitted the construction of mechanical pulp mills that have no liquid effluent. Their only waste is solid waste such as boiler ash. Wood that is chemically processed is chipped. The chips are passed through vibrating screens. Oversized chips and undersized particles (such as chips and dust) are discarded. Accepted chips are stored in huge bins ready for chemical processing. Most pulp produced in the United States is made with the Kraft chemical pulping process (Box 7-1).
To produce paper, the pulp is then screened, cleaned, and mechanically refined. Bales of pulp are dispersed in a huge volume of water so that the slurry is less than 1 percent fiber. The slurry is pumped through a narrow aperture onto a moving wire. The water drains (and is pulled) through the wire to produce a wet pulp mat. Water pulled through the wire is recycled. The wet pulp mat is pressed to remove more water and then is dried over a series of hot rolls to become paper. The water requirements of a paper machine are modest, about 5,000 gal/ton of paper, as much of the water is recycled. The energy requirement, mainly for drying the paper, is roughly 5,000 MJ/ton of paper. This energy often comes from other parts of the mill, such as the mechanical refiners in a mechanical pulp mill or the recovery or waste wood (hog fuel) boilers in a Kraft mill.
Paper Production Recycling
Paper recycling is on the rise, as shown in Figure 7-4. To recycle fiber, the paper is slurried in water and then run through cleaning and screening operations to remove such contaminants as wire, plastics, paper clips, and staples. In some mills the pulp is also deinked. In mills without deinking processes, excess paper-machine white water is sufficient to run the recycle mill. With deinking, fresh water makeup is required. The volume of fresh water makeup can vary widely, from 1,500 gal/ton of pulp to almost 20,000 gal/ton of pulp, depending on the deinking system (Simons, 1994).
BOX 7-1 Kraft Pulping Process
In the Kraft pulping process, wood chips are fed into a digestor where aqueous sodium hydroxide and sodium sulfide, under heat and pressure, break down the lignin that holds wood fibers together. After pulping, the wood becomes individual fibers. Kraft pulping is an energy-intensive process requiring about 9,000 MJ to produce a ton of pulp. The pulp yield of the Kraft process is about 50 percent. This means that about twice as much wood is required to produce a ton of chemical pulp as is needed to produce a ton of mechanical pulp. The chemical and energy recovery of the Kraft process is efficient, however. Over 98 percent of the pulping chemicals are regenerated in the recovery process. The organic matter that is dissolved during pulping (the other 50 percent of the wood that doesn't become pulp) is fired in a recovery furnace. The energy liberated by burning the dissolved organics-typically 14,000 MJ/ton of pulp—is sufficient to run the pulp mill, with some left over. Many mills sell the excess electricity.
Kraft pulp may be used in an unbleached or bleached form. Bleaching is usually done with oxygen, chlorine dioxide, and peroxide. Total chlorine free (TCF) sequences, which replace the chlorine dioxide with peroxide and often ozone, are used but are not as common as the elemental chlorine free (ECF) sequences. In the United States only one pulp mill is TCF. The recent promulgation of the "cluster rule"1 will guarantee that ECF sequences become standard in the decade to come. Current technology does not permit bleach effluent to be recycled. If it is sent through the recovery process, salts build up leading to corrosion and scaling. Hence, the bleach plant accounts for fully half of the effluent that comes from the Kraft mill. Total water use in a Kraft mill is about 20,000 gallons/ton of pulp.
Drivers of Environmental Performance Improvements
As with the other manufacturing industries examined by the committee, regulation has been the dominant driver of environmental performance improvements in the pulp and paper sector. Until the 1980s, the industry's environmental focus was primarily on manufacturing. In the 1980s and 1990s, however, the industry came under additional pressures to improve its environmental performance as concerns related to unsustainable natural resource use, industrial pollu-
tion, and municipal solid waste management2 came to the forefront nationally. These concerns extended across the industry's system of production and consumption as well as upstream to sources and management of the industry's raw
materials (i.e., trees and forests) and downstream to the industry's management of the effects of the nation's increasing paper consumption (Figure 7-1).
Current Use of Environmental Metrics
Sustainable Forestry Practices
Environmental concerns related to acquiring wood from forests center around the method of harvesting, road placement, and local water quality. The industry uses a variety of metrics to track these concerns (Figure 7-5). Plantation forests can create impacts similar to those caused by agriculture (e.g., nonpoint sources of pollution from fertilizers). However, current attention is focused on the larger and longer-term effects of forests and plantations, such as the impairment of natural ecosystems, the health and diversity of species, and the economic resources of fisheries and recreation. The challenges for the pulp and paper industry are to define and refine sustainable forestry practice, adopt these practices, and measure progress toward them.
Forest sustainability has traditionally been assessed by the growth and yield of trees. The goal was to grow trees at least as fast as they are harvested to avoid creating a wood shortage (Boyce and Oliver, forthcoming). Forest practices aim to maximize growth rates and replant clear-cuts rapidly. In addition to clear-cuts, forests are also "thinned" occasionally, with the resulting wood usually being pulped. Trees harvested at a mature age are generally used for solid wood products and composites. Harvesting equipment has been developed to have minimal impact on the forest soil through compaction. Bio-solids and other
forms of fertilizers are sometimes applied to a forest to enhance growth rates. Replanting is generally done with one species of tree. Trees from genetic stocks that have strong, rapid growth rates are used, if possible. The metric used to measure growth rates is cubic meters per hectare per year. Sustainability is determined by comparing the metric with the harvest rate. If a forest is found to grow slower than its targeted rate, the management scheme may be modified or the harvest age prolonged. A related metric relates to reforestation, which is gauged by the fraction of the harvested area that is replanted.
According to Blum et al., (1997), managed regeneration forests and tree plantations affect
- soils and forest productivity, from harvesting or site preparation methods that can deplete nutrient levels over the long term;
- forest streams when activities such as harvesting, fertilizer and pesticide use, and road construction are performed without safeguards, such as adequate buffer strips along streams; and
- plant and animal habitat and species diversity—for example, resulting from the alteration of species composition and the physical structure of vegetation that, at a landscape scale, can reduce the available range of forest habitats.
The ecological effects of specific forestry management practices vary widely among different regions and depend on site conditions. Clear-cutting, for example, has potentially greater impacts in natural forests than in plantations or reforested marginal lands. Decisions to clear-cut natural forest are best guided by such factors as the natural forest disturbance regime (like fire-, wind-, or flood-adapted forest), where large-scale disturbances such as clear-cutting already occur. Other important factors are the characteristics of key forest species and the nature of the site. Alternative methods to clear-cutting, such as selective cutting, are generally less environmentally stressful but often lead to "high grading," where only the best-quality trees are harvested, leaving a low-quality stand. Selective cutting also leads to more frequent entries into a stand, increasing road and skid-trail use and thus more forest disturbances. In terms of land use, selective cutting also requires a larger land base than simple clear-cutting. Finally, the impacts of tree plantations depend on how and where plantations are established. Reforestation (including single-species plantations) on cleared and nonforested lands (such as marginal agricultural crop and pasture lands) is preferable to clear-cutting in many cases (Blum et al., 1997).
Best Management Practices
In general, the basic level of environmental performance is gauged by the extent of adherence to best management practices (BMP) guidelines established
BOX 7-2 Tracking BMP Compliance as a Metric of Forestry Practices
Best management practices (BMP) are voluntary state guidelines intended to protect soil and water resources during forestry operations. Compliance to BMP can be used as a metric for forestry practices. Georgia-Pacific, for example, makes BMP compliance mandatory on all its nearly 6 million acres of forestlands. Forestry consultants are hired to conduct BMP audits on randomly selected tracts of land and use an independent panel of experts to review overall audit practices. In 1996, Georgia-Pacific achieved a 99.4 percent BMP compliance rate in a representative sample of forestry operation on company forestlands.
SOURCE: Georgia Pacific (1998).
by various states. An example of one company's effort to track and report on its BMP compliance is shown in Box 7-2. Most BMP relate to protecting water quality; some cover soil quality during forestry operations. BMP in the Pacific Northwest also address protection of wildlife habitat, natural communities, long-term soil productivity, and other forest values.
The challenge is to develop forestry management plans that produce quality wood while maintaining wildlife habitats and protecting water quality. Harvesting and replanting practices are changing to meet these new sustainability criteria. Replanting may involve multiple species, often with genetically selected species. A variety of harvesting techniques are used, including thinning, clear-cutting, selective cutting, and shelterwood cutting. Harvesting is done in a way that leaves interfaces between forest structures (e.g. wooded areas, meadows, riparian zones). This provides habitats for species, like bats, that roost in mature trees but feed in open areas. Corridors in the cleared areas are left standing to provide passageways between wooded regions. Some trees are left in harvested areas and allowed to grow to old-growth stature. Care is taken to keep riparian zones forested to provide stream temperature control. Snags and other structures are left in the woods and in streams for habitat purposes.
Landscape management is used to meet BMP that address wildlife habitat protection. These practices are used to provide the diversity of forest structures (like clear-cuts and old growth) needed to maintain biodiversity (Boyce and McNab, 1994, Oliver, 1992). Research has shown that a mosaic of forest structures is required to support wildlife variety and maintain watershed health (Hunter, 1990). To maintain levels of biodiversity, the distribution of forest successional stages across a landscape has to remain constant. In order to achieve this, a portion of the landscape is harvested via clear-cut (stand initiation), a portion is
harvested in an intermediate-growth phase (stem exclusion), and a portion is harvested in old-growth stage. If a different mix is desired, to support an endangered species for example, a new distribution may be used. The spatial and temporal scales over which these distributions apply will have an effect on the biodiversity of the region. Similarly, if the patchwork distribution of forest stages in riparian regions is maintained at historical (or known beneficial) levels, the watersheds will remain healthy. Metrics related to this practice are not well developed. New metrics are required to quantify the distribution of the forest successional stages and the distribution of forest structures in a region. Models need to be developed that relate new metrics to sustainability indicators, such as species variation and stream health. The metrics could then be applied at various spatial and temporal scales, depending on the forest sustainability objectives (McCarter et al., 1998).
Sustainable forestry (in the sense of habitat protection) is still experimental. The American Forest and Paper Association (1998c), an industry trade association, has adopted "Sustainability Forestry Principles and Implementation Guidelines." These guidelines designate broad objectives for member companies, leaving each company to design its own implementation to meet the goal. However, there is no specific performance standard. Companies track different things, such as landscape management, environmental auditing, company-specific BMP, special-area programs, logger training, and private landowner assistance programs (Blum et al., 1997), which makes assessment of compliance difficult. The challenge, and priority, in managing the environmental aspects of this part of the paper cycle is in developing a better understanding of the concerns of various stakeholder groups, many of whom have a wide variety of objectives.
One potentially interesting development in the industry, should there be a commitment to the Kyoto Protocol, would be addressing the benefits of carbon sequestration. Sequestration of carbon by trees as they grow would offset carbon dioxide production from paper mills and reduce the industry's production of greenhouse gases (Figure 7-5). An energy-related metric, such as tons of carbon sequestered per BTU used in the production process, could then be used to track the effect of carbon sequestration.
Pulp and Paper Production
Figure 7-6 shows environmental metrics relevant to pulp and paper production. Emissions to air, water, and land are tracked and reported under the standard environmental regulations that cover the other industries discussed in this report. (See Chapter 4 for an overview of these regulations.) For purposes of comparison with other industries, pulp and paper metrics are discussed in terms of emissions; resource use; and reuse, recycle, and disposal.
Air emissions are an important environmental concern in the pulp and paper industry. The primary emissions tracked include carbon monoxide, sulfur dioxide, nitrogen oxides, volatile organic compounds, and particulates. Some pulp and paper companies participate in the Environmental Protection Agency's Industrial Toxics Project (ITP) and are working to reduce emissions of 17 chemicals targeted by ITP. Sulfur emissions, which can cause odor (and public relations) problems, are also monitored.
The industry also tracks emissions to water through such metrics as total effluent flow per unit of production, total suspended solids, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and color, and levels of chlorinated organics, such as dioxin and furans. Chlorinated organics are measured in terms of the weight of absorbable organic halides (AOX) per ton of pulp.
Being the lowest-cost producer is a competitive advantage in an industry that is largely one of commodity production. Resource-related metrics include such things as raw materials and energy use, yield, and percentage of uptime help to facilitate reduction of production costs. Resource-related metrics, therefore, serve both business and environmental improvement goals.
Efficient use of wood as a raw material minimizes wood costs and thus increases the efficiency of a pulp and paper manufacturer's operation. While product quality concerns do not permit a 100 percent utilization rate, having as high a process yield as possible is a distinct business advantage with environmental benefits. Metrics associated with the use of wood as a raw material include percent yield of the processes and annual tons of wood waste disposed of in landfills. Production of recycled paper is resource related and is tracked by comparing nonwood fiber input with wood fiber input.
The pulp and paper industry is the third most energy-intensive industry in the United States. Metrics used to track energy usage are total renewable energy per ton of product and total nonrenewable energy per ton of product. The standard practice of using bark and wood waste and pulping liquor as (renewable) fuel eliminates more than 50 percent of the demand for nonrenewable fossil fuel in the industry as a whole—including in integrated pulp and paper mills (mills in which the paper-making operation is contiguous with the pulping operation) and nonintegrated mills (American Forest and Paper Association, 1994). Other steps that lead to energy conservation include reducing water usage, recovering and reclaiming high-level heat from digesters, improving insulation, and integrating systems that reclaim low-level heat.
Water is intensively used in paper making. A typical Kraft mill requires approximately 20,000 gallons per ton of pulp. Process innovations, such as high-
consistency bleaching and hot-stock screening, require less water. Noncontact cooling, which segregates water from contamination, has also reduced the quantity of water used. Additional savings have accrued from internally recycling water using countercurrent washing and by reusing condensates, cooling and sealing waters, machine white water, and treated effluents. As a result, every gallon of water is reused an average of seven times in the process. The metric for water usage is gallons of water per ton of product.
One company in the industry (Weyerhaeuser Company, 1998) also counts among its resource reduction efforts an initiative to encourage car pooling to reduce commuter trips made by its employees. This and other efforts at reuse, recycling, and resource conservation are examples of activities in the industry that count toward its resource-related metrics.
Reuse, Recycling, and Disposal
Most wood waste is burned as a fuel in boilers. However, bark, wood ash, sludge, and grit remain the chief solid wastes generated at paper mills. Solid waste is measured in terms of total solid waste disposal rates and through goals set for reducing wood waste sent to landfills.
Paper, the primary product of the industry, has been recycled for many years, but recently recycling has begun to receive greater attention. The recycled component of paper is often used as a marketing tool. For production purposes, recovery rates of paper that offset the use of wood fibers are tracked by the industry. In addition, because the integrity of the fiber is critical to the quality of products, the inherent paper-making value of the fiber is also important. There is, however, no reported metric for tracking degradation of fiber resulting from repeated recycling. One reason may be that the industry has several interconnected recycling and reuse options (Figure 7-7).
Table 7-1 summarizes the environmental metrics used in forestry and paper production.
Challenges and Opportunities
The greatest metrics challenge lies in defining sustainable forestry practices. There is a need to move beyond the traditional definition of growth and yield of trees and the current practice of compliance to BMP. Sustainability is a nascent area, and the development of more effective metrics will depend on improved
understanding of ecosystems and the creation of suitable operational principles and practices.
The Minimal Impact Pulp Mill
In an effort to provide a minimal impact vision for the industry, the American Forest and Paper Association (1994) has developed scenarios for a ''Mill of the Future.'' The technological pathways to such as mill are shown in Figure 7-8 and involve improving the pulping and bleaching processes, since bleaching accounts for half of the effluent that comes from a Kraft mill. Current technology does not permit bleach effluent to be recycled. If sent through the recovery process, salts build up, leading to corrosion and scaling.
In the mill of the future, pulping will be done with energy-efficient digesters that promote extended delignification and with additives that enhance the pulping yield. Pulp will be bleached in closed or semiclosed bleach plants. These plants will require relatively small amounts of bleach chemicals with much of the spent liquors being recycled before they are sent through the Kraft recovery system. The bleach plants may contain separation devices to remove nonprocessed ele-
Table 7-1 Metrics Used in Forestry and Paper Production
End Product (Paper)
Growth rate (F1)
Harvest rate (F2)
BMP audit (F4)
Energy (renewable) (ER)
Energy (nonrenewable) (EN)
Wood waste (M)
Recycled content (P1)
Environmental Burden Related
Stream quality (F5)
Soil quality (F6)
Habitat condition (F7)
Water—AOX, BOD, COD, TSS, color, etc.(W1-WN)
Air—Particulate, VOC, NOx, SOx, etc.(A1-AN)
Solid waste (hazardous) (S1)
Solid waste (nonhazardous) (S2)
Environmental incidents Violation notices Citizen complaints
Percent ash in paper (P2)
Human Health and Safety
OSHAa injury/illnesses (HHS1)
Lost work days (HHS2)
Percent of voluntary protection program facilities (HHS3)
Percent of compensation cases (HHS4)
a Occupational Health and Safety Administration.
ments from the spent liquor before they are recycled. It is estimated that water usage in the bleach plant can be reduced to less than 4,000 gallons per ton of pulp (Histed et al., 1996). Effluent from the mill of the future will be significantly reduced with the level of chlorinated organics in bleach plant effluent declining accordingly. The pulping liquor in future mills will be gasified and burned in pulsed combustion furnaces. Such units can improve the energy efficiency of the combustion process by 40 percent while reducing NOx and SOx emissions. Finally, paper produced in the mill of the future will be dried with impulse presses. These presses lower the moisture content of paper by 20 percent, greatly reducing the steam required to dry the paper.
Metrics to assess the performance of the mill of the future will center on total use of resources. Because the mill of the future will use less water, a key measure will be improvement in the rate of reduction and reuse efforts. Another key metric will be energy use per unit of production. However, global climate change-related concerns may drastically affect the use and reporting of energy in the industry.
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