CHAPTER 7
NONHAZARDOUS MATERIAL S RECOVERY—RECYCLING AND COMPOSTING

Materials recovery is considered one of the most promising ways to reduce the amount of nonhazardous waste requiring disposal. The terms recovery and recycling are often used interchangeably. Both mean that a waste material is being reused rather than put in a landfill or incinerated. In general, reuse as a fuel does not fall under the definition of recovery, whereas composting does.

Recycling involves the sorting, collecting, and processing of wastes such as paper, glass, plastic, and metals, which are then refashioned or incorporated into new marketable products. Composting is the decomposition of organic wastes, such as food scraps and yard trimmings, in a manner that produces a humuslike substance for fertilizer or mulch.

Waste recovery offers many advantages. It conserves energy otherwise used to incinerate the waste; reduces the amount of landfill space needed for the disposal of waste; reduces possible environmental pollution because of waste disposal; generates jobs and small-scale enterprises; reduces dependence on foreign imports of raw materials; and replaces some chemical fertilizers with composting material, which further lessens possible environmental pollution. However, recycling sometimes requires more energy and water consumption than waste disposal. It depends on how far the materials must be transported and what is necessary to clean them before they can be reused. Demand for some recyclable materials is weak, making them economically unfeasible to recycle in a market-driven society.

Many Americans view waste recovery primarily as a way to help the environment. For example, if paper is recycled, fewer trees have to be cut down to make paper. State and local governments see recycling as a way to save money on waste disposal costs and prolong the life of landfill space. Thus, waste recovery has both environmental and economic components.

INDUSTRIAL WASTE RECOVERY

As noted in Chapter 6, industrial waste is believed to be the largest nonhazardous waste stream generated in the United States. Furthermore, the U.S. Environmental Protection Agency (EPA; February 22, 2006, http://www.epa.gov/epaoswer/non-hw/industd/questions.htm) estimates that 97% of it is in the form of wastewater. There are opportunities for the recycling of industrial wastewaters, including process rinse waters, cooling water, and scrubber water. Reuse often requires sophisticated treatment technologies to cleanse wastewaters of impurities. These technologies produce wastes, typically sludges, that contain the concentrated impurities stripped from the wastewaters. Nontoxic, industrial wastewater sludges can themselves be reused, for example, in agricultural applications or construction materials.

Nonwastewater industrial wastes can also be recycled either within a facility or between facilities and/or companies. The latter can be accomplished via materials exchange services operated throughout the country. For example, the King County government in Washington State operates IMEX, a free listing service that helps match industrial waste generators with industrial waste users. In 2007 IMEX (September 7, 2007, http://www.govlink.org/hazwaste/business/imex/browse.cfm) included "Available" and "Wanted" listings for a variety of materials, including acids, alkalis, laboratory chemicals, metals, sludges, paints, coatings, solvents, textiles, and wood. Links are provided to dozens of other material exchanges in North America.

The use of wastes from one facility as raw materials at another facility is called by-product synergy (BPS). In 2006 the EPA and the U.S. Business Council for Sustainable Development (a nonprofit association of businesses) began a series of projects intended to boost BPS collaboration between corporations. The projects will establish a system within which businesses can confidentially

TABLE 7.1

exchange information on processes and waste production. It is believed this will encourage greater intercompany recycling of industrial waste streams.

EPA Focus Wastes

The EPA also promotes recycling of industrial wastes through its Resource Conservation Challenge (RCC) project and an industry-government partnership called the Industrial Resources Council (IRC). The RCC project focuses on three waste materials: coal combustion products, foundry sand, and construction and demolition (C&D) waste. Table 7.1 lists potential reuses for these materials. The IRC met in January 2007 to discuss recycling programs and potentials for six target wastes: coal combustion products, foundry sands and slags, iron and steel slags, C&D waste, tire shreds, and pulp and paper industry by-products.

coal combustion products

coal combustion products. Coal combustion products (CCP) include ash, boiler slag (molten ash that crystallizes as it cools), and fine solid materials collected in flue gas treatment equipment. As shown in Figure 7.1, approximately 120 million tons of CCP were generated in 2003, and more than 46 million tons (38.1%) were reused. The American Coal Ash Association reports that most reuse was in cement and concrete production. Other major applications included structural fills and embankments and use as a stabilizer or solidifier for liquid wastes. In 2006 the California Department of Transportation won an award from the EPA for using large amounts of CCP during construction and refurbishing of the Bay Bridge. The department actively supports the use of CCP, in part, because it helps reduce the high greenhouse gas emissions associated with traditional cement manufacture.

foundry sand

foundry sand. Foundries are manufacturing plants in which metal parts are produced in molds. Large amounts of high-quality silica sands are used in the molding and casting operations. Even though the sand can be reused many times, eventually it becomes degraded and must be removed from the process. According to the industry group Foundry Industry Recycling Starts Today (FIRST; 2007, http://www.foundryrecycling.org/Home/IndustryOverview/FAQ/tabid/139/Default.aspx), approximately one hundred million tons of sand are used annually in foundries. About six million tons of sand per year become a waste product because of degradation. This sand can be reused in other industries. In Foundry Sand Facts for Civil Engineers (May 2004, http://isddc.dot.gov/OLPFiles/FHWA/011435.pdf), the U.S. Department of Transportation notes that approximately five hundred thousand to seven hundred thousand tons of foundry sand are used each year in engineering applications, such as embankments, site development fills, and road bases. Additional amounts are used to produce commercially available topsoil.

metal slags

metal slags. Metal slags are composed of minerals and other impurities separated from metals during melting. The slags are quickly cooled to form glassy granules that can be ground into a powder and reused, for example, in cement and concrete. According to the Slag Cement Association (2007, http://www.slagcement.org/shared/), slag was a major component in the rebuilt 7 World Trade Center in New York City and the Georgia Aquarium in Atlanta. Metal slags are believed to be one of the most recycled industrial materials. In the undated report Use of EPA's Industrial Waste Management Evaluation Model (IWEM) to Support Beneficial Use Determinations (http://www.epa.gov/epaoswer/osw/conserve/c2p2/pubs/iwem-report.pdf), Jeffrey S. Melton and Kevin H. Gardner of the University of New Hampshire indicate that up to 100% of blast furnace and steel-making slags were recycled in the United States in the late 1990s.

c&d waste

c&d waste. C&D wastes result from the construction, renovation, and demolition of buildings, roads, and bridges. Typical wastes include concrete, wood, asphalt, drywall, metals, bricks, and glass and cleared trees, stumps, and earth. For building projects the EPA recommends the recovery options shown in Table 7.2. Deconstruction—the careful dismantling of a building to salvage reusable materials—is touted by the EPA in lieu of demolition, which tends to produce waste that must be removed to a landfill. Table 7.3 lists components and materials with a high recovery potential that are typically found in buildings.

C&D debris from roads, bridges, and similar infrastructure is also reusable. According to the Recycled Materials Company, in "World's Largest Recycle Project" (March 2007, http://www.rmci-usa.com/stapleton.htm), in

Figure 7.1

2005 the company completed a six-year project in which 6.5 million tons of concrete, sand, and asphalt from the former Stapleton International Airport in Denver, Colorado, was reclaimed. The world's largest recycling project, as it has been dubbed, sold the materials to federal, state, and municipal governments for reuse in road construction and other applications. The company reports in "The Next

TABLE 7.2

'World's Largest Recycle Project"' (February 2007, http://www.rmci-usa.com/eltoro.htm) that a similar project began in 2006 at the decommissioned El Toro Marine Corps Air Station in Orange County, California. Approximately 3.5 million tons of rubble (technically called hardscape) is expected to be salvaged from that site in a reclamation effort that could last eight years or more.

Some coastal communities have found unique and beneficial uses for C&D debris in artificial reefs. According to the article "Florida County Turns Trash into Artificial Reef" (Waste Age, June 15, 2007), authorities in Collier County, Florida, reported in 2007 that they were nearing completion of a two-thousand-ton artificial reef being constructed approximately nine miles off the coast

TABLE 7.3

TABLE 7.4

in the Gulf of Mexico. The reef consists of clean C&D debris, such as culverts, telephone poles, and junction boxes, that was donated by construction companies.

tire shreds

tire shreds. As described in Chapter 6, scrap tires pose many disposal challenges and environmental risks. Because of their high petroleum content, tires are widely combusted in waste-to-energy facilities. The Rubber Manufacturers Association notes in Scrap Tire Markets in the United States (November 2006, www.rma.org/getfile.cfm?ID=894&type=publication) that just over half of the scraptires generatedin 2005wereusedasfuel. However, civil engineering applications increasingly consume large amounts of recycled tires—an estimated forty-nine million tires in 2005, representing approximately 16% of all scrap tires produced that year. These applications use tire shreds in roads and landfills, septic tank leach fields, and other construction projects. In addition, ground rubber from scrap tires is used to produce new rubber products and as a surface material at playgrounds and sports arenas, such as running tracks. The association indicates that nearly thirty-eight million scrap tires in 2005 (12% of the total) were used in this manner.

ORGANIC BY-PRODUCT RECOVERY

Organic by-products encompass a variety of materials from industrial, commercial, and residential sources. (See Table 7.4.) Wastes with high organic contents can be recycled, most commonly in agricultural applications. Mulch, compost, and soil amendments are also produced from organic by-products.

Biosolids

Biosolids are organic by-products derived from waste-water treatment sludges. Sludges can come from municipal (sewage) plants or industrial facilities with organic-based

TABLE 7.5

processes, such as pulp and paper mills. In either case, some sludge treatment and processing is typically required before biosolids can be reused.

sewage-source biosolids

sewage-source biosolids. The reuse of sewage-source biosolids is regulated by the federal government under Title 40 Part 503 (Standards for the Use or Disposal of Sewage Sludge), which went into effect in 1993. The EPA classifies and regulates biosolids based on their levels of metals and pathogens (disease-causing organisms), their intended reuses, and the extent to which the biosolids will attract vectors (flies, mosquitoes, etc.). There are two pathogen classes. Class A requires that no or virtually no pathogens be present in the biosolid. Class B allows limited levels of certain pathogens. Bio-solids are categorized as shown in Table 7.5. Exceptional Quality (EQ) biosolids meet the strictest limits and are permitted for all types of land application with no legal restrictions on reuse. EQ-class biosolids can be sold to the public, for example, in lawn and garden stores.

In "Survey of Organic Wastewater Contaminant in Biosolids Destined for Land Application" (Environmental Science and Technology, vol. 40, no. 23, September 2006), which reports on the presence of nonbiological organic contaminants in biosolid samples, Chad A. Kinney et al. raise questions about the effectiveness of Part 503. Kinney and his colleagues tested nine different biosolids produced by sewage treatment plants in seven different states. More than fifty organic contaminants were detected in the samples, including disinfectants and fragrances. Even though the concentrations were not believed to be harmful, Kinney and his collaborators stress that additional study is needed to determine the level and fate of nonbiological organic chemicals in biosolids. Critics believe that the EPA's biosolid limits are outdated—they were crafted in the late 1980s—and need to be updated to reflect the range of complex organic chemicals found in sewage in the 2000s, such as disinfectants that are added to soaps.

pulp and paper industry by-products

pulp and paper industry by-products. Pulp and paper industry by-products are one of the wastes targeted by the EPA via the IRC for greater recycling. Bill Thacker of the National Center for Air and Stream Improvement, in "Management of Byproduct Solids Generated in the Pulp and Paper Industry" (January 23, 2007, http://www.epa.gov/epaoswer/non-hw/imr/irc-meet/03-paper.pdf), states that approximately fifteen million dry tons of pulp and paper mill by-products are produced annually. This waste stream includes wastewater treatment plant sludge, boiler ash, fine materials collected in flue gas treatment equipment, causticizing residues, wood waste, and rejects from the pulping and papermaking processes. Thacker notes that only about a quarter of the by-products are recycled, primarily through land application. Most of the by-products go to disposal, for example, in landfills.

agricultural waste

agricultural waste. The Agricultural Research Service, in "FY-2006 Annual Report Manure and Byproduct Utilization National Program" (2006, http://www.ars.usd.gov/SP2UserFiles/Program/206/NP206ManureandByproductUtilization.doc), indicates that more than one billion tons of agricultural wastes are produced annually. Organic by-products within this waste stream include manure and animal bedding (e.g., hay). Manure is rich in nutrients, such as nitrogen and phosphorus, that have beneficial uses as fertilizing agents. Thus, land application is a common recovery method. Figure 7.2 shows waste handling practices, including land application, at a typical dairy farm.

The availability of sufficient and easily accessible land for application of organic agricultural wastes is a pressing concern. Noel Gollehon et al. note in "Confined Animal Production and Manure Nutrients" (Agriculture Information Bulletin, no. 771, June 2001) that in 2001 approximately one-fourth of the nation's livestock operations lacked adequate on-farm land for application of the waste stream at acceptable rates. Even though most counties in which these operations were located did contain sufficient crop acres on other farms for application of the excess manure, transport problems were widely reported. The U.S. Department of Agriculture recommends that acceptable alternatives, such as energy production, be developed to mitigate reusability challenges associated with manure.

MUNICIPAL SOLID WASTE RECOVERY

Municipal solid waste (MSW) is the everyday garbage produced by homes and businesses. The EPA conducts detailed tracking of the generation and recovery of this nonhazardous waste stream. The EPA notes that Americans recycled seventy-nine million tons of MSW in 2005, accounting for 32.1% of total MSW generated. (See Figure 7.3.) Recycling rates for various materials are shown in Table 7.6. The materials with the highest recovery rates were nonferrous metals excluding aluminum (72.4%), yard trimmings (61.9%), and paper and paper-board (50%). By contrast, recovery rates were low for food wastes (2.4%) and plastics (5.7%).

The EPA does not break down recovery rates by state. However, in "The State of Garbage" (BioCycle, April 2006), Phil Simmons et al. estimate the state-by-state recycling rates in 2004. According to Simmons and his coauthors, the states with the highest recycling rates in 2004 were Oregon (45.8%), Minnesota (43.2%), New York (43%), Tennessee (42.2%), and Washington (40.5%).

Municipal Solid Waste Components Recovered

paper

paper. The paper industry has been at the leading edge of the recycling revolution. Used paper-based products can be de-inked in chemical baths and reduced to a fibrous slurry that can be reformulated into new paper products. Paper can undergo this process several times before the fibers become too damaged for reuse. Paper products vary greatly in the type (hardwood versus softwood) and length of fibers that are used to make them. Recycled papers must typically be sorted into particular usage categories (e.g., newsprint or fine writing papers) before being reprocessed.

Figure 7.4 shows EPA estimates of the tons of paper (and paperboard) products generated as municipal waste and the tons recovered between 1960 and 2005. Overall, the recovery rate for 2005 was 50%. However, according to the EPA, in Municipal Solid Waste in the United States: 2005 Facts and Figures (October 2006, http://www.epa.gov/msw/pubs/mswchar05.pdf), there were wide variations in rates for specific paper products. For example, the EPA states that newspaper had a recovery rate of 89.2%. This was the highest rate for any product within this category. Recovery rates were also high for corrugated boxes (71.5%) and office papers (62.6%). Most other paper products had moderate recovery rates falling within the 10% to 40% range. By contrast, paper products such as tissue papers and towels, milk cartons, and paper plates and cups had negligible recovery rates (less than 0.1%).

glass

glass. Waste glass can be melted down and formed into new glass products over and over without losing its structural integrity. Virgin raw materials, such as sand, limestone, and soda ash, are added as needed to formulate new glass products. However, colored glass cannot be easily de-colored, as paper is de-inked. This means that glass products must be sorted by color before reprocessing.

FIGURE 7.2

Figure 7.5 shows EPA estimates of the tons of glass products generated as municipal waste and the tons recovered between 1960 and 2005. Most glass that becomes MSW is from bottles and jars manufactured for food and drink products. Glass generation rates generally declined between 1980 and 2003 because of competition from the plastics industry for these markets. Glass recovery increased throughout the 1980s and early 1990s and then experienced a slight decline.

FIGURE 7.3

metals

metals. Metal recycling is as old as metalworking. Coins and jewelry made of gold and silver were melted down in ancient times to make new coins with images of the current ruler. Metal objects were generally considered valuable and were frequently sold or given away, rarely simply discarded. When metal objects could not be repaired, they could be melted down and fashioned into something else. This practice continues in modern society. In general, metals must be sorted by composition before reprocessing.

Figure 7.6 shows EPA estimates of the tons of metal products generated as municipal waste and the tons recovered between 1960 and 2005. According to the EPA, ferrous metals (iron and steel) comprise the largest category of metals in MSW. They are primarily used in durable goods such as appliances, furniture, and tires. Aluminum is used extensively in drink and food cans and packaging materials. Lead, zinc, and copper fall under the category "other nonferrous metals." They are found in batteries, appliances, and consumer electronics.

Metals recovery was relatively flat until the mid-1980s, when it began increasing dramatically. Recovery leveled off during the late 1990s. Detailed EPA data in Municipal Solid Waste in the United States show that recovery rates differ greatly from metal to metal. More than 72% of nonferrous metals (excluding aluminum) in the 2005 municipal waste stream were recovered, compared with only 35.8% of ferrous metals and 21.5% of aluminum.

plastics

plastics. Plastic products are manufactured from chemical resins molded into various shapes. There are dozens of different resins in common use, each with a different chemical formulation. Even though waste plastic products can be melted down and reformulated into new products, sorting by resin type must first be performed.

Figure 7.7 shows EPA estimates of the tons of plastic products generated as municipal waste and the tons recovered between 1960 and 2005. In 1960 there were virtually no plastic products in MSW. In Municipal Solid Waste in the United States, the EPA indicates that in 2005 MSW contained 28.9 million tons of plastic products. This massive increase in generation was accompanied by incredibly low rates of recovery. Only 5.7% of all plastic products generated in MSW during 2005 were recovered. This is about 1.6 tons of plastic recovered. The plastics recovery rate has hovered between 5% and 6% since 1995.

TABLE 7.6

Detailed EPA data show that the recovery of some plastic products is much higher than others. In 2005, 34.1% of polyethylene terephthalate soft drink bottles were recovered from municipal waste. Nearly 29% of high-density polyethylene milk and water bottles were recovered. However, recovery rates for other plastic products were low.

electronic equipment

electronic equipment. Computers and other electronic devices contain materials that are valuable for reuse, particularly metals, plastics, and glass. (See Figure 7.8.) The most common metals in personal computers are aluminum, steel, and copper. Small amounts of precious metals, such as gold, palladium, platinum, and silver, are also found in computer circuit boards. Some of the metals used in personal computers (antimony, arsenic, cadmium, chromium, cobalt, lead, mercury, and selenium) are classified as hazardous by the Resource Conservation and Recovery Act and cannot be disposed of in municipal solid waste landfills. This is discussed further in Chapter 8.

The primary source of plastics in electronic devices is computer casings. Plastic can be melted down to produce new materials or used as a fuel in certain industrial processes. Most of the glass content of computers is in cathode ray tube monitors. This glass contains lead, which is a hazardous material. However, the glass can be reused to produce new cathode ray tubes.

Figure 7.9 provides generation and recovery data for electronic wastes in MSW for various years between 2000 and 2005. Over 2.6 million tons of electronic equipment were generated as municipal waste in 2005 and only 330,000 tons were recovered.

containers and packaging

containers and packaging. The EPA reports that in 2005, 76.6 million tons of containers and packaging were generated, comprising 31.2% of municipal solid waste. In 2005, 39.8% of containers and packaging were recovered, up slightly from 37.9% in 2000. The containers and packaging recovery rate was only 10.5% in 1960. The 2005 recovery figures for containers and packaging included 63.3% of steel, 58.8% of paper and paperboard, 36.3% of aluminum, 25.3% of glass, 15.4% of wood, and 9.4% of plastics.

Municipal Solid Waste Recycling Programs

The successful recycling of any product within municipal solid waste depends on the success of three key components in the recycling process:

• Collection and sorting of the products to be recycled
• Processing and manufacturing technologies to convert waste materials into new products
• Consumer demand for recycled products and those containing recycled materials

Lack of any one of these components seriously jeopardizes recovery efforts for a particular material within the MSW stream. These three factors are represented by the three arrows in the international symbols used to show that a product is recyclable or contains recycled materials. A discussion of the various MSW recycling programs follows.

curbside programs

curbside programs. Curbside programs are those in which recyclable items are collected from bins placed outside residences. According to the EPA, in Municipal Solid Waste in the United States, there were more than eighty-five hundred curbside recycling collection programs in the United States in 2005. The EPA estimates that these programs served 79% of the population in the Northeast and 67% of the population in the West. Much smaller percentages were reported for the Midwest (43%) and South (23%). Overall, 48% of the U.S. population had access to curbside recycling programs in 2005.

drop-off centers

drop-off centers. Drop-off centers for recyclable materials are operated by various entities, including cities, grocery stores, charitable organizations, and apartment complexes. Typically, they accept a broader range

FIGURE 7.4

of materials than curbside collection programs. The number of drop-off centers around the country is unknown.

Buy-Back Centers and Deposit Systems

Two systems provide a cash incentive to encourage recycling. These are buy-back centers and deposit programs. Buy-back centers are typically businesses that pay cash for recovered materials, such as scrap metal, aluminum cans, or paper.

Deposit programs charge consumers a deposit or fee on beverage containers at the time of purchase, typically a few cents. The deposit can be redeemed if the container is returned empty for reuse. The EPA indicates in Municipal Solid Waste in the United States that in 2005 there were ten states operating deposit-type programs: Connecticut, Delaware, Hawaii, Iowa, Maine, Massachusetts, Michigan, New York, Oregon, and Vermont. Furthermore, in California consumers do not pay a deposit on containers, but they can redeem them. Deposit amounts vary by state. For example, in 2007 Californians could redeem bottles containing less than twenty-four ounces for five cents each. Larger bottles had a redemption value of ten cents each.

Materials Recovery Facilities

Materials recovery facilities (MRFs) sort collected recyclables, process them, and ship them to companies that can use them to produce new or reformulated products. For example, a materials recovery facility may sort and crush various types of glass recovered from curbside programs and then ship the processed glass to a bottle factory, where it can be used to produce new bottles.

MRFs vary widely in the types of materials they accept and the technology and labor they use to sort and process recyclables. Most MRFs are classified as low technology, meaning that most of the sorting is done manually. High-technology MRFs sort recyclables using eddy currents (swirling air or water), magnetic pulleys, optical sensors, and air classifiers.

The EPA indicates in Municipal Solid Waste in the United States that there were 504 materials recovery facilities operating in the United States in 2005, which processed a total of approximately 50,000 tons per day.

commercial recyclables collection

commercial recyclables collection. According to the EPA, commercial establishments are responsible for

FIGURE 7.5

the largest quantity of municipal solid waste recycled in the United States. The most commonly recycled materials in the business sector are old corrugated containers and office papers. Grocery stores and other retail outlets are the primary recyclers of old corrugated containers, which are typically picked up by paper dealers. Likewise, many businesses collect used office paper for collection by paper dealers.

The Role of Government in Municipal Solid Waste Recycling

The oldest recycling law in the United States is the Oregon Recycling Opportunity Act, which was passed in 1983 and went into effect in 1986. The act established curbside residential recycling opportunities in large cities and set up drop-off depots in small towns and rural areas.

A growing number of states require that many consumer goods sold must be made from recycled products. In addition, many states have set recycling/recovery goals for their municipal waste. In 1989 Maine adopted a goal to achieve 50% recycling by 1994. The deadline has been extended several times, and in 2005 it was extended to 2009.

For recycling programs to work, there must be markets for recycled products. To help create demand, some states require that newspaper publishers use a minimum proportion of recycled paper. Many states require that recycled materials be used in making products such as telephone directories, trash bags, glass, and plastic containers. All states have some kind of "buy recycled" program that requires them to purchase recycled products when possible.

The states also use other incentives for recycling. Some states provide financial assistance, incentive money, or tax credits or exemptions for recycling businesses. Furthermore, almost all states bar certain recyclable materials (such as car and boat batteries, grass cuttings, tires, used motor oil, glass, plastic containers, and newspapers) from entering their landfills.

The federal government also helps create a market for recycled goods. The Resource Conservation and Recovery Act requires federal procuring agencies to purchase recycled-content products designated by the EPA in its overall Comprehensive Procurement Guidelines (CPG). EPA guidance regarding the purchase of recycled-content products is also included in Recovered Materials Advisory Notices, which are published periodically and include recommended recycled-content ranges for CPG products that are commercially available.

COMPOSTING

Composting is a recovery method in which plant-based waste materials are isolated and allowed to decompose,

FIGURE 7.6

producing an organic-rich substance suitable for use as a soil amendment. Typical compost wastes include grass and garden cuttings, leaves, and kitchen refuse, such as potato peels and coffee grounds. Meat scraps and other animal-based wastes are not recommended for composting, because they can attract scavenging animals.

Natural decomposition of a pile of organic waste can be a long process. Composters can accelerate the process through a variety of techniques, including layering plant wastes with manure or soil, watering the compost, and turning or churning it with garden implements to provide more oxygen. These methods can produce a usable compost material within a few months.

Gardeners mix compost with the soil to loosen the structure of the soil and provide it with nutrients, or spread it on top of the soil as a mulch to keep in moisture. Because compost adds nutrients to the soil, slows soil erosion, and improves water retention, it is an alternative to the use of chemical fertilizers. Compost created on a large scale is often used in landscaping, land reclamation, and landfill cover and to provide high-nutrient soil for farms and nurseries.

Yard waste is especially suitable for composting because of its high moisture content. Over the past few decades composting yard trimmings has become an accepted waste management method in many U.S. locations. The practice got a huge boost beginning in the late 1980s, when many states banned yard trimmings from disposal facilities. In Municipal Solid Waste in the United States, the EPA states that in 2005 there were 3,474 publicly operated yard-trimming composting programs operating in the United States. An unknown amount of backyard composting also takes place.

THE HISTORY AND CURRENT STRENGTH OF RECYCLING

For a quarter-century after the first Earth Day (April 22, 1970), recycling advocates pleaded their case to skeptical decision makers in the interest of environmental benefit. As with any business, recycling is subject to the cyclical highs and lows of supply and demand. In the early years of recycling the economy was unable to use all the plastic, paper, and other materials that were recovered. It was difficult for private recycling companies to make a profit. Instead of earning money from recycling, the programs cost them money. Some cities even started dumping their recycled materials into landfills because they could not sell them. Eventually, markets grew for some recycled materials, particularly in the paper sector.

FIGURE 7.7

FIGURE 7.8

Market growth has been helped by the widespread public support that recycling receives. Riley E. Dunlap of the Gallup Organization reports in "The State of Environmentalism in the U.S." (April 19, 2007, http://www.galluppoll.com/content/?ci=27256&pg=1) that 89% of survey participants reported voluntarily ¼ recycling such items as newspapers, aluminum cans, and glass. This value was 90% in 2000.

Some analysts believe that recycling rates for municipal solid waste have reached a plateau and cannot easily be increased because of the supply and demand imbalance in recycled-content markets. They prefer to focus on source reduction, that is, the reduction of the amount of municipal waste produced in the first place. One method for reducing MSW generation is a principle called Extended Producer Responsibility (EPR). EPR regulations require manufacturers and producers to take some responsibility for the final disposition of their products. This provides an incentive for products and their packaging to be more recoverable and contain less toxic materials. EPR is a cornerstone of recycling requirements in Canada, Japan, and the European Union.

FIGURE 7.9