Papers and Abstracts page 

# Products from Recycled Fibers - A U.S. Perspective

Thomas E. Hamilton, Joanne T. Alig and Robert H. Falk

Abstract
The issue of sustainability underlies most concerns surrounding forests and their use in the 21st century. Recycling offers a rational way to conserve forest resources, reduce demands on other natural resources and ecosystems, and still meet huma n needs for wood-based materials. However, markets for recovered raw materials constitute a major barrier to successf ul recycling. The USDA Fo rest Service, Forest Products Laboratory, is researching and developing ne w technologies that efficiently turn recovered wood and paper fiber into higher value products. Such research includes assessing the available recovered fiber supply, developing technologies to produce wood-based products suitable for housing and other industrial applications, de veloping technologies to improve th e utilization of recovered paper fibers, conducting economic analyses, and ensuring th at products made from recycled fiber meet accepted performance standards. From a U.S. pe rspective, creating and implementing these new technologies is best accomplished through effective partnerships between gove rnment, academia, and industry.
Keywords: Recycling, waste, recovery, reuse.

Introduction
Forests contribute in many ways to our well being: Forests play a crucial role in watersheds by p roviding slope stability; aid in cl imate regulation; furnish habitat fo r wildlife; provide human leisure and recreation; render nontimber resources such as floral greens and ediblemushrooms; and supply timber resources for producing fuel, making furnitur e, constructing homes, building bridges, and making p aper. In short, the demands on our forests are numerous , and we need to ensure that we are using them wisely and in a sustainable manner.
When the concept of sustainable development was pr esented in the 1987 United Nations report, "Our Common Future," it clearly cont ained the message that the envi ronment and economics cannot be treated separately and that material needs must be met in ways that preser ve the biosphere. In 1992, a report of the National Commission on the Environm ent, "Choosing a Sustainable Future" (World Wildlife Fund 1992), endorsed the 1987 United Nati ons report and went one step further. The Commission stated that "long-term gr owth depends on a sound environmen t, and resources to protect the environment will come from econo mic strength." The point here is important - it is a circular relationship: a strong economy depe nds on a healthy environment and a healthy environment depends on a strong economy. The U.S. forest products industry c ontributes positively to the U.S. economy. In nearly every U.S. state, the forest products industry is one of the top te n manufacturing employers. In total, nearly 1.4 x 106 p eople are employed in lumber and wood products an d the paper and allied pr oducts industries in the United States (U.S. Bureau of Census 1994). Toge ther, these industries produce nearly US$200 x 109 in shipments every year, making up more than 7% of all manufacturing in the United States (U.S. Page 1 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmDepartment of Commerce 1993).
Our dependency on forest products is growing. Nearly half (by weight) of all industrial raw materials used in the United States (steel, concrete, plas tics) is wood based. Reside ntial construction is the dominant market for most timber products in th e United States, and a 13% increase in lumber consumption per housing unit is projected in the next 45 years. In total, lumber consumption is projected to grow approximately 30%, to 74.0 x 109 board feet (260 x 106 m3) in 2040. Consumption of structural panels (softwood plywood, oriented strandboard, and waferboard) is expected to reach 42.3 x 109 ft 2 (3.9 x 109 m2) by 2040, an increase of 70% above 1990 consumption levels. Consumpt ion of nonstructural panels (hardwood plywood, insulating board, hardboard, and particle board) is also projected to increase to 28.4 x 109 ft2 (2.6 x 109 m2) by 2040, an increase of 28% above 1990 levels. Finally, pulpwood cons umption is expected to grow more than 53% in the next 45 years. In total, U.S. timber cons umption in terms of roundw ood volume is expected to reach 26.5 x 109 ft3 (750 x 106 m3) in 2040, more than 40% above 1990 consumption levels (Haynes et al. 1995).
In the past, growing demand for products translat ed into greater emphasis on timber harvesting. Although we acknowledge that great strides in cons erving resources can be made by reducing our material use, we must be realistic in recognizi ng that the demand for products will not diminish. Population in the United States is expected to increase from 262 to 338 x 106 by 2025; world population is expected to increase from 5.6 to 8.9 x 109 by 2025. On a worldwide basis, this means that we face the need to find new ways to conserve our forest resour ces. In addition, in the United States we are facing increasing restrictions on harvesting of forest lands. This raises th e question of how to meet growing demand for wood-based products while still meeting our sustainability goals. Recycling of wood fibers p rovides an opportunity to meet both objectives to provide the raw material used in making woo d -based p roducts and to conserve forest resources. Assuming recycled paper products can be substituted for virgin wood material when producing paper and pape rboard, it has been esti mated that accelerated recycling has the potential to offset the need to harvest 400 x 106 ft3 (11.3 x 106 m3) of sawtimber and pulpwood (Haynes et al. 1995).
U.S. Recycling
Most industrialized nations have been actively pur suing new technologies to recover more materials from postconsumer and postindustrial waste streams. In the United States, this effort gained momentum in the late 1980s when the growing volumes of material disposed in landfills resulted in public pressure to reduce the availability of land for new dump si tes. In 1993, 44% of the municipal solid waste generated in the United States c onsisted of paper, paperboard, and wood products (U.S. EPA 1994). Because of this large percentage of municipal solid wa ste, U.S. state and local laws and regulations were p assed that required recove ry and reuse of many woo d -based products.
Currently, every U.S. state regulates recycling or solid waste management. St ate governments encourage reuse of recovered material thr ough demand-side mandates such as minimum content standards, tax incentives, green labeling, and procurement standards. State legislators have also pursued mandates to increase the supply of recovered materials. They have prohibited products from being disposed in landfills and adopted recycling goals that specify a percentage of the waste stream to be recovered for recycling, reduced at the sour ce, composted, or otherwis e diverted from landfills.
The U.S. pulp and paper industry ha s also adopted recovery goals to increase the amount of paper material recovered from the municipal solid wast e stream. In 1990, the U.S. paper industry proposed a 40% recover y g oal b y 1995. That g oal was met in 1994 when 38.6 x 106 tons of paper were recovered Page 2 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmin the United States - just over 40% of all paper us ed. The U.S. paper industry has since set a new goal to recover for recycling and reuse half of all paper used by the year 2000.
In addition to conserving our resour ces, re-cycling offers many societal benefits. Recovery of materials can extend the life of existing landfills and offset the need to find new landfills. Cities throughout the United States are finding that recycling offers empl oyment and, when successful , brings in revenues to help lower the cost of refuse collection. Further, processing recovered paper fi ber requires less energy than processing virgin materials, thus generati ng less carbon emissions (Skog 1995) and helping the U.S. government meet its objective of keeping net emi ssions of carbon to levels no greater than those in 1990.
The USDA Forest Service, Forest Products Laboratory (FPL), recognizes the benefits of recycling and is researching and developing new tec hnologies that efficiently turn re covered wood and paper fiber into higher value products. Such resear ch includes assessing the available recovered fiber supply, developing technologies to produce wood-based products suitab le for housing and other industrial applications, developing technologies to improve the utilization of recovered paper fibers, conducting economic analyses, and ensuring that products made from recycl ed fiber meet accepted pe rformance standards.
Waste Resource Supply Information
Success in developing technolog ies to produce value-added products from recycled wood waste is dependent upon many factors, including the availability of a consistent and relatively uniform raw material source. Detailed raw materi al resource information is a necessary first step in developing any new technology or system to converta raw material into a usable product. Adequate short- and longterm raw material supplie s must be available at reasonable cost s for a technology to be commercially adopted and implemented. Factors affecting the econom ic supply of recyclable raw materials include amounts and types of material genera ted, condition and quality of the ma terial, extent of commingling o f materials, separability of materials, types of contam inants present, physical location of the material, and costs of acquisition, concentration, and transportation. Li kely changes in these factors must be evaluated to determine possible effect s on raw material supply.
The capability to economically a ssemble a continuous supply of raw material requires innovations in collection, sorting, and distribution of waste materials. Directing materials to the highest value use is essential. In addition, a manufacturing firm must have some assurance of long-term supply, which includes both a continuous flow of suitable raw materi als and the ability to compete economically in the raw material market place.
Recycled Wood-Based Composite Products
There are many opportunities to develop the t echnology needed to make composite products from recycled wood-based fiber. The fiber can be used alone to make low cost/high performance composites. Alternatively, recycled fiber can be combined with other recycled materi als, such as plastics, to produce mixtures, compatibilized blends, and alloys. Finally, wood-based fiber can be combined with inorganic materials. Researchers at FPL lead the formation of a task force composed of government, industry and academia to provide a framework for research to develop composite products using recycled fiber (Rowell et al. 1993).

Several essential issues need to be addressed to fully utilize post- consumer wood and paper wastes in composite products. First, characteri zation of the recyclable materials and their levels of contamination are needed. Secondly, the raw material needs to be c onverted into a form suitable for the manufacturing Page 3 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmp rocess. Also, any effect of existing residual cont amination on the manufactur ing process needs to be quantified. Most importantly, th e link between raw material ch aracteristics and final product p erformance must be established. Fi nally, evaluation, testing, and design standards must be developed to use these products.
In this paper, we discuss several existing and devel oping technologies that have the potential to produce recycled wood-based products suitable for use in housing and other industrial applications. One benefit of these technologies is that they pr ovide an outlet for recycling other ma terials, such as some grades of p lastic, or using agricultural fibers for which there is currently no economic use.

D ry-Formed Wood Composites
Dry-formed wood composites can be made from recove red wood fiber in much the same way as conventionally produced particle-based composites (e.g., partic leboard, hardboard, medium-density fiberboard). Dry-formed processi ng involves breaking wood waste into strands, flakes, particles, or fibers and reassembling them into ne w forms with the aid of an adhesive . An important part of particlebased composite panel manufacture from virgin w ood is a consistent and homogeneous raw material source to ensure uniform panel properties. Because th e raw materials being considered here are derived from waste, the many forms and sources of w ood waste will likely pos e special processing considerations. For example, wast e wood from demolition sites may be contaminated with lead-based p aint, nails, stones, plastic, gypsum , and concrete. In addition to th is surface contamination, the wood waste may contain preservative or fire-retardant chemicals. Research and development to efficiently p rocess these raw materials will result in new, value-added products.

Wet-Formed Structural Fiber Products
Wet-formed structural fiber products can be pr oduced from basic papermaking technologies (pulp slurry). Using a three-dimensiona l pulp-molding process, researchers at the FPL have produced a structural component called Spaceboar d. It is anticipated that the Space board technology will be used to p roduce a variety of housing components. This proc ess can readily accept r ecycled wood fibers, and although now limited to rectangular panels, has the potential for both curvilinear and th ree-dimensional solid-formed products. This molding potential could gr eatly enhance design flexib ility for architects and engineers.
The FPL is also considering two po tential technologies to utilize recy cled wood fiber using wet-formed p rocesses. One technology is a pulp extrusion process that has the potential to produce products with various dimensions and cross secti ons. Potential products developed with this process might include decorative molding and trim products and lumber substitute products.
Another technology is a wet-formed fiber-based proc ess that involves shapi ng structural components through the winding of paper sheet stock. This lami nating process incorporates existing paper sheetforming technology and is familiar to most builders that have used paper tubes for concrete formwork. This type of process has the potential to utiliz e low-grade recycled pape r stock. Because circular, rectangular, and other efficient cr oss-sectional shapes can be form ed, a number of potential housing components can be produced with this laminating process.
Wood-Plastic Composites
Wood-plastic composites include those made by binding recycled wood fibers with recycled plastics, synthetic fibers, and resins. These combinations ca n produce a variety of composite building products. Page 4 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmRecycled woo d

- b ased fiber and plastics can be combined to make a wide spectrum of products, ranging from very inexpensive, low-perf ormance composites to expensive, high-performance materials. Fiber technology, bonding performance, and fiber modification can be used to manufacture wood-plastic composites that have uniform density, durability in adverse environments, and a high level of strength.
The primary applicatio n for fiber-thermoplastic co mposites is in extrusion molding. The natural fiber improves the rigidity and strength of the plastic and lowers the cost of the final products.
Utilizing thermoplastics in composites has been li mited to nonstructural uses by creep, which results from thermal or long-term loading deformation. However, thermoplastics (which melt when heated) can be converted to thermosetting materials (which are cr oss-linked and unable to melt ), so that it would be p ossible to make creep-resistive structural products using recycled thermoplastics. Research and development to overcome such limitations can greatly increase the use of wood-plastic composites.
Wood-Inorganic Composites
Another recycling opportunity is to bond recovered wood and othe r postconsumer materials with inorganic materials. Recycled particles or fibers of wood held together with an inorganic binder, such as Portland cement and gypsum, form a composite that can be used in a variety of structural and architectural applications, such as lightweight concrete. Virgin- b ased wood and cement composites have found wide use in Europe, although their use is scarce in North America.
Compared with conventional wood-building mate rials, wood-inorganic composites offer unique advantages in that these composites combine the a dvantageous characteristics of both the wood fiber and mineral matrix. These composites have good fire , noise, decay fungi, and insect resistance.
The use of inorganic mate rials to bind recovered w ood fiber, chips, and particles has proven to be technically feasible in commerci al products such as sound insula tion board, gypsum, fiberboard, and low-density cement-bonded wood building blocks. This range of products can be extended if means are developed to convert waste wood into optimal particle sizes.
Recycled Solid-Wood Products
One source of lumber that has great potential for reutilization is th e "old" lumber and timbers from dismantled structures. In addition to the millions of single-family residential buildings in the United States, thousands of World War II military buildings th at contain millions of boardfeet of usable lumber and timbers are slated for demolition. This demoliti on material is an attract ive recyclable because it takes little energy to put it in reusable form.
The lumber and timbers salvaged from the demo lition of existing wood structures are becoming a building material with increased value. This is because large-sized virgintimbers are not readily available from contemporary forests. Also, salvaged timbers, whil e sometimes containing bolt holes and other defects, are us ually well seasoned.
The potential for utilizing old lumber or timber s depends not only on the economic feasibility of recovery compared with disposal, but the acceptance of used products in new construction. Because the grade of lumber is correlated to its structural performance and build ing officials require some measure of assured performance (typically gi ven by the grade stamp on virgin lumber), a system is needed to g rade old lumber. Page 5 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmRecovered Paper Technolo g ies
The use of recovered paper fiber to make new paper products has increas ed steadily over the past several years. However, there are several technical barriers to recovery and reuse of high grade paper materials. Research is needed to improve the ability to rem ove toners and other contaminants from recovered p aper, improve fiber strength, and improve the bleaching process of recovered fiber. Furthermore, making paper with recycled fiber generates more sl udge than making paper from virgin fiber. Research is needed to examine new uses for this sludge and develop new technol ogies that produce fewer byproducts.

I

mproving Toner and Contaminant Remova l
Few paper products found in municipal solid waste contain only fiber. Recovered paper can contain toners, adhesives, fillers, dyes, meta l foils, plastics, and dirt. Use of fibers from recovered paper to p roduce new paper products requires separating fibers from contaminants and cleaning. Success in developing technologies to impr ove toner and contaminant remova l can greatly increase the raw material potential of m unicipal solid waste.
One problem is that photocopiers a nd laser printers use nylon or plas tic-based toners that, under high heat, bond to xerographic and photocopier paper. R ecycling xerographic and photocopier paper into p rinting and writing paper is difficult and costly. FPL is examining the use of commercially available biodegradable enzymes to enhance conventional removal processes. This enzymatic deinking process uses a low amount of chemicals, resulting in a clean er process water with effluent that is lower in oxygen demand and less toxic. Further, enzymes are readily biodegraded and do not cause problems in environmental cleanup. This technol ogy separates toner from fibers more effectively, improves pulp brightness and drainage, thus allowing for great er production.

I

ncreasing Fiber Strength
Recycled fiber is weaker than virgin fiber as a re sult of the changes that occur during the drying phase when the fiber is first made into paper. The dryi ng dehydrates the fibers under high temperatures and p ressure. This hardens the fiber surfaces and shrinks the pores that allow water to pass back and forth between fibers. These changes reduce the flexibility a nd the ability of the fibers to bond to one another, leaving short, stiff fibers that produce weak paper.
Three technologies have the ability to improve the strength of recovered fiber. One technology involves soaking recovered paper fibers in various chemical treatments before disi ntegration. This technology restores the bonding potential of the dried fibers.
A second technology involves using sc reens to separate the shorter an d stiffer recovere d paper fibers from those that are longer and more flexible. This technology allows for th e use of the longer more flexible fibers to enhance paper strength, without creating a toxic effl uent. A third technology allows an inexpensive inorganic filler to be substituted for some fiber in paper pulps so that the resulting paper is stronger and less costly to produce. This process, called fiberloading, cr eates a reaction that causes the filler to form within the fiber walls wh ere it will not interfere with the bonding ability of the fiber. Technologies to increase fi ber strength of recovered paper will ensure that recycled paper is comparable with paper made from virgin materials. This will enhance consumer acceptance and use of recycled paper products.

B leaching Recovered Fibers Page 6 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmOne primary concern in using recovered fiber to make new paper products has been the brightness of the end product. In the past, the most commonly used aid for repulping and bleaching recovered paper was sodium hypochlorite. However, in creased environmental concerns regarding the use of chlorine compounds in paper mills have resulted in the needto find alternative repulping aides (Kapadia 1992).
The FPL research is examining other compounds (suc h as peroxymonosulfuric acid and its salts) that show promise as bleaching agents fo r recovered paper fiber. Some of these compare in effectiveness to using chlorine, but do not produce the same byproducts.
Research is also underway to test the potential for using enzymes to remove lignin and bleach the pulp. If successful, this technology may be used in converting old corrugated containers (or fiberboard), which have a high recovery rate, into higher valued printing and writing papers.

D ecreasing Sludge
Making paper from recovered fiber generates more sl udge than making paper from virgin fiber. Sludge, a byproduct of pulp and papermaking, is a heterogene ous mixture of water, short or damaged wood cellulose fibers, and other contaminants. In a rece nt study by Scott et al. ( 1995), the energy and environmental costs associated with seve ral disposal processes were analy zed. The study considered alternative incineration technologies, including appl ying the sludge to forest or agricultural lands. Results from this study provide valuable information about options for disposing of sludge from papermaking.
In addition to finding new uses for sludge, new tech nologies can result in a decrease in the amount of sludge generated. One technology uses ultrafiltration sc reens to recapture fiber that escapes from the p ulp as water is used to wash ink from the pulp. This technology improves th e recovery of fiber and reduces the waste. In addition, the fiberloading technology discussed previ ously not only improves p aper strength, but reduces the amount of sludge a nd emissions generated over conventional methods.
Economic Analysis
Economic analysis of curr ent and future trends in recycling t echnology and markets provides important information for researchers and policymakers. Forest Service economists are studying long-term recycling trends and their broad economic, environm ental, and energy impacts. The FPL researchers have collaborated with academic and industry partne rs to develop an economic model called the North American Pulp and Paper Model (NAPAP Mode l). This model provide s long-range economic assessments of the North American pulp and paper sector. It has been used to examine the effects of recycling on pulp and paper markets by simulating t echnology for using recovered fiber and virgin wood fiber and makes projections of timber supply a nd demand, growth, inventory, and prices. A similar model for the solid wood sectors of the U.S. and Canadian economies is under development.

Performance Evaluations and Standards
Although there is great opportunity to utilize recycled wood-based materials using the described p rocessing technologies, the products produced from them must perfor m satisfactorily. For building and p aper products, performance standards ensure a product's acceptability.
Each of the 6,000 grades of paper and paperboard products has established performance and quality standards that determine acceptabili ty in the marketplace. These U.S. standards are set by manufacturing associations for each paper grade. A systematic analysis is needed to prioritize and target those grades o f p aper that are best suited to accept recycled fibers . This will mean assessing the effect of recycled Page 7 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmcontent on paper performance in produc ts made from recycled fibers.
Recycled products us ed in housing and other industrial app lications must also meet performance standards. Standards for building products result in an assurance of public safety as well as the facilitation of regulatory acceptance of the developed products and building systems. Therefor e, evaluations of structural performance, fire p erformance, environmental performan ce (including moisture effects and durability), insulative and acoustical properties, and toxici ty hazards are needed. The establishment of testing, design, and evaluation standards to measure and maintain this performance is also required.
Standards organizations, such as the American Soci ety for Testing and Materi al (ASTM), the American N ational Standards Institute (ANSI), and the Internat ional Standards Organizati on (ISO), develop test standards and performance criteria for comparing properties across a range of products intended for a specific application. The development of such "cons ensus" standards is the keystone to equitable treatment of propertie s across product lines and provides th e consumer confidence in product p erformance and safety.
Partnerships -Making Recycling a Reality
Cooperative partnerships are esse ntial for the timely implementati on of new technologies. The FPL has already experienced many successes in creating partnerships for recycl ing technologies. Partners include individual companies, universiti es, and government agencies such as the U.S. Army and the U.S. Department of Energy. In addition, g overnment research labs , such as the FPL, often work with state and local government agencies whose primary goal is to achieve increased recycling. State and local governments implement programs to ensure a steady s upply of recovered material s. Researchers provide technical expertise to industry and can help facilitate the developmen t of new technologies to utilize these recovered materials. Industry can then use th ese new technologies to process recovered materials into high value products with performance st andards that ensure acceptability and use in the marketplace. By working together to recover, reproc ess, and reuse re-cyclable materials, we can make great strides in ensuring the success of recyclin g efforts and conserving our resources for future generations.
Concluding Remarks
In the United States, we are making rapid strides in recycling wood fibers. In fact, we are ahead of schedule if we look at past goals and the timetables to reach them. However, much remains to be done. We have outlined the following six areas where t echnology is needed to make expanded recycling a reality:

z Available supply assessment

z Composites from wood and paper

z Solid wood product reuse

z Paper-to-paper technology

z Economics research

z Performance evaluations a nd standards development
We believe that science is the key to expand ing recycling. We also believe that a close science/manufacturing partnership is needed to make further recycling a reality: science to provide the technology and industry to implement it. If successful, the public will benefit through a broader array of Page 8 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htmp roducts and conservation of forest resources.

References
Haynes, R.W., Adams, D.M., and Mills, J.R ., 1995: The 1993 RPA timber assessment update. RMGTR-259. U.S. Department of Agriculture, Fore st Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado.
Kapadia, Pankaj C., 1992: A non-c hlorine repulping aide. In: Pro ceedings of the 1992 Papermakers Conference. Atlanta, GA: TAPPI Press.
Rowell, R.M., Spelter, H., Arola, R.A. et al., 1993: Opportunities for composites from recycled wastewood-based resources: a problem analysis and research plan. Fo rest Products Journal 43(1): 55-63.
Scott, G.M., Smith, A., and Abubakr, Said, 1995: La ndfill alternatives in th e pulp and paper industry. Prepared for the Proceedings of the 1995 TAPPI R ecycling Symposium; New Orleans, LA. Atlanta, GA: TAPPI Press.
Skog, Kenneth, 1995: Personal communication. May.
United Nations, 1987: Our Common Future. United Nations World Commission on Environment and Development, New York: Oxfo rd University Press.
U.S. Bureau of Census, 1994: Statis tical abstract of the United Stat es 1994 (114th edition). U.S. Bureau of Census, Washington DC.
U.S. Department of Co mmerce, 1993: 1991 Annual survey of manufactures. Industry series. 1987 economic censuses compact disk. Volume I. Releas e 1E. United States Department of Commerce, Bureau of the Census, Data User Services Division, Washington DC.
U.S. EPA, 1994: Characterization of municipal solid waste in the United States: 1994 update. U.S. Environmental Protection Agency, Municipal and I ndustrial Solid Waste Division, Office of Solid Waste. EPA530-R-94-042.
World Wildlife Fund, 1992: Choosing a sustainable future, the report of the National Commission on the Environment. Washington DC.
OE Nov 21, 199 6 Page 9 of 9 Hamilton: Products from RecycledFibers - A U.S. Perspective

7/30/2008 http ://www.metla.fi/iufro/iufro95abs/rs p 21.htm