CHAPTER 6
NONHAZARDOUS WASTE

All waste materials not specifically deemed hazardous under federal law are considered nonhazardous wastes. The vast majority of waste produced in the United States is not inherently hazardous. It includes paper, wood, plastics, glass, metals, and chemicals, as well as other materials generated by industrial, commercial, agricultural, and residential sources. Even though these wastes are not defined as hazardous, improper management of them poses significant risks to the environment and human health. Therefore, the handling, transport, and disposal of nonhazardous wastes is regulated by the government, largely at the state and local level.

LAWS REGARDING WASTE

In 1965 the U.S. government passed the Solid Waste Disposal Act, the first of many solid waste management laws. It was amended several times, most notably in 1976, with the Resource Conservation and Recovery Act (RCRA). Its primary goal was to "protect human health and the environment from the potential hazards of waste disposal." The RCRA is also concerned with reducing the amount of waste generated, ensuring that wastes are managed properly, and conserving natural resources and energy. The RCRA primarily covers hazardous waste, which makes up only a small portion of all waste generated. State and local governments are mainly responsible for passing laws concerning nonhazardous waste, although the federal government will supply money and guidance to local governments so they can better manage their garbage systems. The RCRA consists of ten subtitles. (See Table 6.1.)

RCRA Subtitle D assigns to the states responsibility for permitting and monitoring landfills for municipal solid waste and other nonhazardous wastes. Regulations established under Subtitle D describe minimum federal standards for the design, location, and operation of solid waste landfills to protect the environment. The states can develop their own permitting programs, so long as they include the federal landfill criteria. The U.S. Environmental Protection Agency (EPA) has the authority to review and approve the state programs.

WASTE TYPES AND AMOUNT ESTIMATES

The RCRA definition of solid waste includes garbage and other materials ordinarily considered "solid," as well as sludges, semisolids, liquids, and even containers of gases. These wastes can come from many different sources. Table 6.2 lists various types of wastes that may be considered nonhazardous. It should be noted that these categories are not all-inclusive; for example, certain batteries and light-bulbs disposed by businesses fall under hazardous waste regulations. Thus, the extent to which a particular waste is deemed nonhazardous depends on both its physical and chemical nature and the source from which it comes.

It is difficult to calculate exactly how much non-hazardous waste is generated in the United States and what becomes of it. Under the RCRA the federal government collects data primarily on hazardous waste. In addition, the EPA estimates the production of municipal solid waste (or common garbage) each year using surveys, studies, population data, and other information. However, municipal solid waste composes only a small portion of all nonhazardous waste generated. The vast majority of nonhazardous waste produced in this country is not tracked or estimated by the federal government but falls under varying state and local regulatory schemes.

NONHAZARDOUS INDUSTRIAL WASTES

Nonhazardous industrial wastes are believed to be, by far, the largest single type of waste produced in the United States. The EPA (February 22, 2006, http://www.epa.gov/epaoswer/non-hw/industd/questions.htm) notes that "an old survey" estimates that 7.6 billion tons of this waste are produced annually. Approximately 97% of this amount is in the form of wastewaters. (Chapter 9

TABLE 6.1

discusses wastewater management in detail.) Thus, approximately 228 million tons per year of nonwastewater industrial waste is generated.

Figure 6.1 shows an estimate made in 1997 of the breakdown of nonhazardous waste by industry in the United States. Major waste producers at that time included the pulp and paper, metal, chemical, and mining industries.

Many big manufacturing plants have sites on their own property where they dispose of waste or treat it so it will not become dangerous. Still others ship it to private disposal sites for dumping or for treatment. Smaller manufacturers might use private waste disposal companies or even the city garbage company.

The Texas Tracking System

State and local governments have regulatory responsibility for the management of most nonhazardous wastes. However, different states have different regulatory schemes. For example, Texas categorizes nonhazardous industrial wastes into three classes based on their potential harm to the environment and human health. Class 1 wastes are the most tightly regulated. They include asbestos, ash, and various solids, sludges, and liquids contaminated with nonhazardous chemicals. The most recent report available on Texas industrial waste was published in August 2000 and includes data for 1997. According to Needs Assessment for Industrial Class 1 Nonhazardous Waste Commercial Disposal Capacity in Texas (2000 Update) (http://www.tceq.state.tx.us/assets/public/comm_exec/pubs/sfr/038_00.pdf), nearly eighty-three million tons of Class 1 waste were generated in Texas in 1997. The vast majority (96%) of the waste was liquid.

Class 2 wastes include containers that held Class 1 wastes, depleted aerosol cans, some medical wastes, paper, food wastes, glass, aluminum foil, plastics, Styrofoam, and food packaging resulting from industrial processes. Class 3 wastes include all other chemically inert and insoluble substances such as rocks, brick, glass, dirt, and some rubbers and plastics.

Texas industries do not have to report how much Class 2 or Class 3 wastes they generate or how they dispose of it. However, municipal solid waste landfills are required to report the receipt of all industrial waste.

AGRICULTURAL WASTES

Agricultural wastes are made up primarily of organic-based wastes, such as livestock manure, urine, and bedding material. According to the Agricultural Research Service, in "FY-2006 Annual Report Manure and Byproduct Utilization National Program" (2006, http://www.ars.usda.gov/SP2UserFiles/Program/206/NP206ManureandByproductUtilization.doc), more than one billion tons of organic agricultural wastes are produced annually in the United States. The management of livestock waste, particularly on large agricultural facilities, is an issue of concern because of the potential environmental impacts. (See Table 6.3.)

TABLE 6.2

FIGURE 6.1

Runoff of nutrients from manure collection and storage facilities poses a threat to the water quality of streams, lakes, and rivers. For this reason the waste management practices of certain agricultural operations are regulated by the federal government under the Clean Water Act. (Water issues are discussed in detail in Chapter 9.)

CONSTRUCTION AND DEMOLITION DEBRIS

Construction and demolition (C&D) debris is a non-hazardous waste stream generated from the construction, renovation, and demolition of buildings, roads, and bridges. According to the EPA (May 3, 2007, http://www.epa.gov/epaoswer/non-hw/debris-new/index.htm), its constituents include the following:

• Concrete
• Wood (from buildings)
• Asphalt (from roads and roofing shingles)
• Gypsum (the main component of drywall)
• Metals
• Bricks
• Glass
• Plastics
• Salvaged building components (doors, windows, and plumbing fixtures)
• Trees, stumps, earth, and rock from clearing sites

TABLE 6.3

Even though it is not specifically regulated by the federal government, the EPA, in "Construction and Demolition (C&D) Debris: Basic Information" (February 22, 2006, http://www.epa.gov/epaoswer/non-hw/debris-new/basic.htm), reports that an estimated 136 million tons of C&D building-related debris was generated in 1996. Additional "significant" quantities are believed to be generated from the construction of roads and bridges and land clearing before construction. Most C&D debris is managed through disposal at specially designated landfills.

MEDICAL WASTE

Medical waste attracted widespread attention in the mid-1980s, when used needles and similar items washed up onto beaches in the Northeast. Even though most medical waste is regulated by state governments, Congress responded with the Medical Waste Tracking Act of 1988. This temporary act called for better tracking and disposal methods for medical waste. The act, which expired in 1999, defined medical waste as "any solid waste that is generated in the diagnosis, treatment, or immunization of human beings or animals, in research pertaining thereto, or in the production or testing of biologicals." Thus, sources include health care facilities, medical research facilities, veterinary clinics, and medical laboratories. In "Medical Waste"

(January 31, 2007, http://www.epa.gov/epaoswer/other/medical/), the EPA gives the following as examples of medical waste under the federal definition:

• Bloody bandages
• Used surgical gloves and instruments
• Used needles (medical sharps)
• Biological cultures and associated equipment, such as glassware and swabs
• Surgically removed body parts, such as tonsils and limbs
• Used lancets

The EPA notes that there are varying state definitions of medical waste that can include additional waste streams not previously specified. There are different regulatory categories of medical wastes, including infectious, hazardous, radioactive, and general wastes. The EPA estimates that infectious medical waste makes up only 10% to 15% of all medical wastes generated. Likewise, hazardous and radioactive wastes are believed to make up small fractions of the total medical waste stream. These two streams are regulated by the federal government. Infectious and general medical wastes are regulated at the state level. The EPA reports that more than 90% of infectious medical waste is incinerated. The federal government regulates emissions from medical waste incinerators.

SPECIAL WASTES

When the RCRA regulations were promulgated in 1987, the EPA included a list of six wastes deemed "special wastes" and exempted them from classification as hazardous wastes until further studies could be conducted. As of June 2007 many studies on the toxicity of these wastes have been conducted, and the following are considered special wastes under federal law:

• Cement kiln dust, which is the fine-grained highly alkaline dust removed by air pollution control devices during the production of cement
• Wastes generated during the exploration, development, and production of crude oil, natural gas, and geothermal energy
• Wastes produced from the burning of fossil fuels (coal, oil, and natural) and including all ash and slag (metal waste) and any particulates removed from flue gases
• Twenty waste streams that are generated during the processing of minerals to remove them from the native ore
• Most wastes generated from the extraction and beneficiation of "hardrock" (metal ores and phosphate rock) and twenty specific mineral processing wastes

These waste streams are also known as high-volume, low-toxicity wastes. Even though some components, particularly cement kiln dust, can be reused within the processes involved or sold for commercial purposes, most special wastes are disposed in land-based disposal units, such as landfills, waste piles, or surface impoundments.

MUNICIPAL SOLID WASTE

The EPA defines municipal solid waste (MSW) as "common garbage or trash." MSW includes items such as food scraps, paper, containers and packaging, appliances, batteries, and yard trimmings. These types of wastes are generally collected and managed by local municipal agencies. MSW does not include construction and demolition wastes, automobile bodies, sludge, combustion ash, and industrial process wastes.

Determining the amount and types of MSW generated in the United States is a difficult task. People are not required to track or report how much MSW they produce or what it contains. The EPA uses information supplied by trade groups and industrial sources, combined with estimated product life spans and population and sales data, to estimate how much and what types of MSW are generated.

According to Table 6.4, Americans produced 245.7 million tons of MSW in 2005, down slightly from 247.3 million tons in 2004. The tons of MSW generated annually increased dramatically between 1960 and 2000. Most of this increase occurred during the 1960s, 1970s, and 1980s. In 1960, 88.1 million tons of MSW were generated. Over the next three decades MSW generation increased on average by 33% per decade. However, the 1990s witnessed a slowdown in this rate of increase. MSW generation increased by only 16% between 1990 and 2000 and then began leveling off, increasing by only 3% between 2000 and 2005.

This trend is also reflected in the per capita (per person) values for MSW generation. In 1960 each American generated on average 2.68 pounds of MSW per day. This value steadily increased until 1990, when it reached 4.50 pounds per day. As shown in Figure 6.2, this rate leveled off during the 1990s, fluctuating between 4.50 and 4.63 pounds. In 2005 per capita generation was 4.54 pounds per day. This number has remained fairly constant since 1990.

MSW Composition

Figure 6.3 shows EPA estimates of the breakdown of MSW produced in 2005 by waste type. Paper was the largest single component by weight, composing 34.2% of the waste stream. It was followed by yard trimmings (13.1%), food scraps (11.9%), plastics (11.8%), metals (7.6%), rubber, leather, and textiles (7.3%), wood (5.7%), glass (5.2%), and other MSW (3.4%). The top five categories—paper, yard trimmings, food scraps, plastics, and metals—together made up 79% of the MSW generated in 2005.

paper

paper. The EPA estimates in Municipal Solid Waste in the United States: 2005 Facts and Figures (October 2006, http://www.epa.gov/msw/pubs/mswchar05.pdf) that in 2005 there were eighty-four million tons of paper generated as MSW. The paper category includes many paper and paper-board (boxboard and containerboard) products. Corrugated boxes make up the bulk of this category in terms of the tons generated. In 2005 MSW included 30.9 million tons of corrugated boxes, representing 12.6% of paper waste.

TABLE 6.4

Newspapers, office papers, commercial printing papers, milk cartons, and junk mail are other major contributors to the paper category. This category does not include gypsum wall-board facings (which are classified as construction and demolition debris) or toilet tissue (which goes to sewage treatment plants).

yard trimmings

yard trimmings. In Municipal Solid Waste in the United States, the EPA estimates show that in 2005 there were 32.1 million tons of yard trimmings generated as MSW. Yard trimmings include grass, leaves, and tree and brush trimmings from residential, commercial, and institutional sources. According to the EPA, yard trimmings are assumed to contain an average by weight of 50% grass, 25% leaves, and 25% brush.

In the past the EPA based its estimates of yard trimming generation on only sampling studies and population and housing data. During the 1990s it began to take into account the expected effects of local and state legislation on yard trimmings disposal in landfills. For example, in 1992 only eleven states and the District of Columbia had laws prohibiting or discouraging residents from disposing yard trimmings at landfills. In 2005 twenty-one states and the District of Columbia had such legislation in place. The EPA believes that this increased the use of mulching lawnmowers and the practice of backyard composting of yard trimmings, thus reducing the amount of yard trimmings in MSW.

food scraps

food scraps. The EPA, in Municipal Solid Waste in the United States, estimates that in 2005 there were 29.2 million tons of food waste generated in MSW. Included in the EPA's definition of food scraps are uneaten food and food preparation scraps from residences, commercial establishments (such as restaurants and grocery stores), institutional sources (such as school cafeterias and prisons), and industrial sources (such as factory cafeterias). Food scraps generated by industrial sources that produce and package food products are not included in MSW.

plastics

plastics. The EPA estimates in Municipal Solid Waste in the United States that in 2005 there were 28.9 million tons of plastic materials in the MSW waste stream. The word "plastics" refers to materials made from particular chemical resins that can be molded or shaped into various products. Plastic materials are found in a wide variety of products, including containers, packaging, trash bags, milk jugs, cups, eating utensils, disposable diapers, sporting and recreational equipment, and many common household items (such as shower curtains). In addition,

FIGURE 6.2

there are plastic components in appliances, computers, furniture, luggage, and many other consumer products.

metals

metals. According to EPA estimates in Municipal Solid Waste in the United States, in 2005 there were 18.7 million tons of nonhazardous metals generated in MSW. Ferrous metals (iron and steel) made up 74% of this category by weight, followed by aluminum at 17% and other nonferrous (non-iron) metals at 9%. Ferrous metals are widely used in durable goods such as appliances and furniture. Ferrous metals used in transportation vehicles (such as automobiles) are not included in this category. Steel is also used to manufacture food cans, barrels, and drums. Aluminum found in MSW is most commonly in beer and soft drink cans, food cans, and as foil wrap.

consumer electronics

consumer electronics. Consumer electronics include televisions, computers, videocassette recorders, compact disc and digital video disc players, digital and video cameras, radios, answering machines, telephones and cellular phones, fax machines, printers, scanners, and miscellaneous other equipment. Historically, the EPA has lumped such products under the category "other miscellaneous durable goods."

In 2000, for the first time, consumer electronics were categorized separately, and it was estimated that 2.1 million tons entered the MSW stream. In 2005 this value climbed to 2.6 million tons, representing 1.1% of the total MSW generated. Even though this percentage is small, it is expected to increase quickly during the 2000s as more electronic products reach the end of their useful lives.

Disposal of electronic goods in MSW poses environmental risks because of the presence of metals and other hazardous contaminants in the products. Some states, therefore, forbid electronic waste from MSW, as described in Chapter 8.

Historical Trends in MSW Composition

Since 1960 paper has consistently been the largest single component of MSW generated. The EPA notes in Municipal Solid Waste in the United States that paper's share of the total was virtually identical in 1960 and 2005: 34%.

FIGURE 6.3

In 1960 plastics made up only 0.4% of the total MSW generated. By 2005 they made up 11.8% of the MSW total. Manufacturers are increasingly using plastic to package their products because plastic is so easy to use and shape. As a result, plastics are the fastest-growing proportion of MSW in the United States. The EPA predicts that the amount of plastic thrown away will continue to increase.

The total number of pounds of plastic in MSW increased from only 390,000 tons in 1960 to 28.9 million tons in 2005. Most of these plastics (a family of more than forty-five types) are nonbiodegradable and, once discarded, remain relatively intact for decades and even centuries. They do not break down through organic processes.

The percentage of yard trimmings in the MSW total decreased from 22.7% in 1960 to 13.1% in 2003. However, the tons of yard trimmings in MSW actually increased during this period.

MSW Management

The three primary methods for the management of MSW are:

• Land disposal
• Combustion (or incineration)
• Recovery through recycling or composting

Land disposal involves piling or burying waste materials on or below the ground surface. This is primarily

FIGURE 6.4

done at facilities called landfills. Incineration is a disposal method in which MSW is burned at high temperatures, while combustion is the burning of waste to produce energy. Recycling is the reuse of a material in another product or application. Composting is a method of decomposing yard trimmings and other biodegradable wastes for reuse as fertilizer. Recycling and composting are discussed at length in Chapter 7.

According to the EPA, in 2005 land disposal was the most common method used to manage MSW in the United States. (See Figure 6.4.) More than half (54.3%) of the MSW generated was discarded, going to land disposal, whereas 32.1% was recovered and 13.6% was combusted.

The EPA does not break down MSW disposal methods by region or state. However, Phil Simmons et al., in "The State of Garbage" (BioCycle, April 2006), provide regional information on disposal methods for 2004. Landfilling is most prevalent in the Rocky Mountain and midwestern states. In general, these states are less densely populated, thus they generate less MSW and have more space for landfills than many other states. Combustion and incineration were more common in the New England and mid-Atlantic states. These states are much more densely populated and have few areas available or suitable for landfilling.

The EPA reports in Municipal Solid Waste in the United States that the percentage of MSW landfilled has decreased dramatically from 93.6% in 1960 to 54.3% in 2005. In 1960 only 6.4% of MSW was recycled. This value was 23.8% in 2005. Composting and combusting of MSW were virtually nonexistent in 1960. In 2005, 13.6% of MSW was combusted and 8.4% was composted.

Municipal Landfills

Municipal (or sanitary) landfills are areas where MSW waste is placed into and onto the land. Even though some landfilled organic wastes will decompose, many of the wastes in MSW are not biodegradable. Landfills provide a centralized location in which these wastes can be contained.

how organic matter decomposes in landfills

how organic matter decomposes in landfills. Organic material (material that was once alive, such as paper and wood products, food scraps, and clothing made of natural fibers) decomposes in the following way: first, aerobic (oxygen-using) bacteria use the material as food and begin the decomposition process. Principal by-products of this aerobic stage are water, carbon dioxide, nitrates, and heat. This stage lasts about two weeks. However, in compacted, layered, and covered landfills, the availability of oxygen may be low.

After the available oxygen is used, anaerobic bacteria (those that do not use oxygen) continue the decomposition. They generally produce carbon dioxide and organic acids. This stage can last up to one to two years. During a final anaerobic stage of decomposition lasting several years or decades, methane gas is formed along with carbon dioxide. The duration of this stage and the amount of decomposition depend on landfill conditions, including temperature, soil permeability, and water levels.

In "Five Major Myths about Garbage and Why They're Wrong" (The Smithsonian, July 1992), William Rathje and Cullen Murphy report on a twenty-year study called the Garbage Project. Conceived in 1971 and officially established at the University of Arizona in 1973, the Garbage Project was an attempt to apply archaeological principles to thestudy of solid waste. About 750 people processed more than 250,000 pounds of waste, excavating fourteen tons of it from landfills.

Among the Garbage Project's findings is the discovery that even though some degradation takes place initially (sufficient to produce large amounts of methane and other gases), it then slows to a virtual standstill. Study results reveal that an astonishingly high volume of old organic matter remained largely intact. Even after two decades, one-third to one-half of supposedly degradable organics remained in recognizable condition. Rathje and Murphy conclude that well-designed and well-managed landfills, in particular, seem more likely to preserve their contents than to transform them into humus or mulch.

Landfills and the Environment

methane

methane. Methane, a flammable gas, is produced when organic matter decomposes in the absence of oxygen. If not properly vented or controlled, it can cause explosions and underground fires that smolder for years. Methane is also deadly to breathe. The RCRA requires landfill operators to monitor methane gas.

Rathje and Murphy note that "for 15 or 20 years after a landfill has stopped accepting garbage, the wells vent methane in fairly substantial amounts. Then methane production drops off rapidly, indicating that the landfill has stabilized."

Methane gas can be recovered through pipes inserted into landfills, and the gas can be used to generate energy. According to the EPA, in Municipal Solid Waste in the United States, as of April 2007 there were 424 operational landfill gas-to-energy projects in the United States. (See Figure 6.5.) The EPA's Landfill Methane Outreach Program estimates that approximately 560 other landfill sites presented attractive opportunities for project development.

Landfill Design Standards

The RCRA standards require landfill operators to do several things to lessen the chance of polluting the underlying groundwater. Groundwater can become contaminated when liquid chemicals or contaminated rainfall runoff seep down through the ground underneath the landfill. This liquid is called leachate.

The RCRA requirements are as follows:

• Landfill operators must monitor the groundwater for pollutants. This is usually accomplished with a groundwater monitoring well system.
• Landfills must have plastic liners underneath their waste, as well as a leachate collection system. (See Figure 6.6.)
• Debris must be covered daily with soil to prevent odors and stop refuse from being blown away.
• Methane gas (a by-product of decomposition) must be monitored, which is usually accomplished with an explosive-gas monitoring well.
• Landfill owners are responsible for cleanup of any contamination.

Landfills are not open dumps but managed facilities in which wastes are controlled. MSW is often compacted before it is placed in a landfill and covered with soil. Modern landfills have liner systems and other safeguards to prevent groundwater contamination. When they are full, landfills are usually capped with a clay liner to prevent contamination. (See Figure 6.6.)

Imports and Exports of Garbage

Lack of landfill space has encouraged some municipalities to send their garbage to other states. Even though shipments do occur across the Mexican and Canadian borders, the vast majority of U.S. MSW is managed within the United States.

FIGURE 6.5

Simmons and his colleagues indicate that importing and exporting MSW from state to state is common. In 2004 Maryland exported the most MSW (2.6 million tons), followed by New Jersey (2.5 million tons) and New York (2.2 million tons). Other states exporting more than one million tons of MSW included Washington (1.5 million tons), Massachusetts (1.4 million tons), and North Carolina (1.1 million tons). The chief MSW importers were Pennsylvania (10.6 million tons), Michigan (6 million tons), Virginia (5.9 million tons), and Ohio (3.2 million tons). The vast majority of imported MSW was landfilled.

Several states have tried to ban the importing of garbage into their states. In 1992 the U.S. Supreme Court ruled in Chemical Waste Management v. Hunt (504 U.S. 334) that the constitutional right to conduct commerce across state borders protects such shipments. Experts point out that newer, state-of-the-art landfills with multiple liners and sophisticated pollution control equipment have to accept waste from a wide region to be financially viable.

Trends in Landfill Development

Before using landfills, cities used open dumps, areas in which garbage and trash were simply discarded in

FIGURE 6.6

huge piles. However, open dumps produced unpleasant odors and attracted animals. In the early 1970s the number of operating landfills in the United States was estimated at about twenty thousand. In 1979, as part of the RCRA, the EPA designated conditions under which solid waste disposal facilities and practices would not pose adverse effects to human health and the environment. As a result of the implementation of these criteria, open dumps had to be closed or upgraded to meet the criteria for landfills.

Additionally, many more landfills closed in the early 1990s because they could not conform to the new standards that took effect in 1993 under the 1992 RCRA amendment. Other landfills closed as they became full. According to the EPA, the number of landfills available for MSW disposal decreased dramatically from 7,924 in 1988 to 1,654 in 2005. (See Figure 6.7.)

Landfilling is expected to continue to be the single most predominant MSW management method. In the coming decades it will be economically prohibitive to develop and maintain small-scale, local landfills. There will likely be fewer, larger, and more regional operations. More MSW is expected to move away from its point of generation, resulting in increased import and export rates.

Landfill protection methods will likely become stronger in the future with more options for leachate and gas recovery. To make landfills more acceptable to neighborhoods, operators will likely establish larger buffer zones, use more green space, and show more sensitivity to land-use compatibility and landscaping.

Bioreactors: Accelerated Landfilling

Traditional landfills are often called dry tombs, because the waste is kept as dry as possible to reduce the

FIGURE 6.7

possibility of leaching contaminants to the environment. Biodegradation under these conditions can take decades. A new approach is offered in bioreactor landfills—landfills in which moisture is purposely added to accelerate biodegradation. Bioreactor landfills can operate using aerobic (oxygen-based) or anaerobic (oxygen-free) processes or a combination of the two. In aerobic bioreactor landfills oxygen as well as moisture are introduced to the waste pile.

The EPA (August 31, 2007, http://www.epa.gov/epaoswer/non-hw/muncpl/landfill/bioreactors.htm) promotes the development of bioreactor landfills and touts research showing the following advantages for them over conventional landfills:

• Much faster decomposition and biological stabilization of waste, typically taking years, instead of decades
• Reduced toxicity of the waste
• Lower costs for leachate disposal
• Less space required because of the higher density of the waste
• Significant increase in landfill gases produced for energy production
• Lower costs for landfill care after closure

The primary disadvantage of bioreactor landfills is their higher capital (construction) costs compared with traditional landfills. Furthermore, particular attention must be paid to preventing leachates from escaping from the waste piles.

Bioreactor.org notes in "Bioreactors around the World" (February 5, 2007, http://www.bioreactor.org/world.html) that in 2007 the following thirteen bioreactor landfills were in operation in the United States:

• California—Yolo County
• Florida—Alachua County Southeast, Highlands County, New River Regional Landfill in Raiford, and Polk County Landfill in Lakeland
• Kentucky—Outer Loop Landfill
• Michigan—Clare County
• Mississippi—Plantation Oaks in Sibley
• Missouri—Columbia
• New Jersey—Haneman Environmental Park in Egg Harbor Township
• North Carolina—Buncombe County
• Virginia—Virginia Landfill Project XL Demonstration Project

INCINERATION AND COMBUSTION

Incineration and combustion are popular disposal choices for nonhazardous wastes. They both involve heating waste to high temperatures. In the past waste wasb urned in incinerators primarily to reduce its volume. During the 1980s

FIGURE 6.8

technology was developed that allowed waste to be burned for energy recovery. Use of waste as a fuel is more commonly called combustion; however, both terms are used interchangeably. The EPA refers to waste combustion as a waste-to-energy (WTE) process.

Figure 6.8 shows a typical WTE system. At this facility, the trucks dump waste into a pit. The waste is moved to the furnace by a crane. The furnace burns the waste at a high temperature, heating a boiler that produces steam for generating electricity and heat. Ash collects at the bottom of the furnace, where it is later removed and taken to a landfill for disposal. Figure 6.9 illustrates the combustion process, which produces both gaseous emissions and solid waste (in the form of ash).

Incineration of Various Wastes

According to the EPA, in Municipal Solid Waste in the United States, in 2005 there were 88 WTE facilities operating in the United States that incinerated 33.4 million tons of MSW, representing 13.6% of the total MSW generated that year. (See Figure 6.4.) In "Solid Waste Combustion/Incineration" (August 17, 2007, http://www.epa.gov/epaoswer/non-hw/muncpl/landfill/sw_combst.htm), the EPA estimates that combusting MSW reduces the amount of waste by 90% in volume and 75% in weight. According to the U.S. Department of Energy (DOE), in 2006 waste-derived energy made up just over one-half of 1% of the nation's total energy supply, producing 404 trillion British thermal units (BTUs) of power. (See Figure 6.10.)

Scrap tires have always posed a disposal problem for the United States. Scrap tires accumulated in landfills or uncontrolled tire dumps can pose health and fire hazards. Scrap tires do not compress in landfills and provide breeding grounds for a variety of pests. In fact, some states ban the disposal of tires in landfills. In 1985 Minnesota passed the first state legislation dealing with scrap

FIGURE 6.9

tires. Other states followed suit. The Rubber Manufacturers Association reports in Scrap Tire Markets in the United States (November 2006, www.rma.org/getfile.cfm?ID=894&type=publication) that several waste manage-companies invested in tire-to-fuel projects, and by 1990 up to twenty-five million scrap tires per year were burned for fuel. Furthermore, it notes that 155 million scrap tires were burned as fuel during 2005 in specialized WTE facilities.

Industries are increasingly choosing WTE as a means to reduce the amount of waste that requires disposal and for energy benefits. For example, Shaw Industries (2007, http://www.shawfloors.com/Shaw-Environmental/Innovation), a major manufacturer of carpet and wood flooring, operates a WTE plant at its manufacturing facility in Dalton, Georgia. The WTE plant burns up to twenty-one million pounds of wood and carpet waste per year that ordinarily would be landfilled. It also produces heat that is used within the manufacturing process.

MSW Incineration Emissions

Incineration of MSW fell into disfavor during the 1980s because of concerns about air emissions from the combustion process. These emissions can include mercury and other heavy metals and acid gases (such as hydro-chloric acid) from the burning of paints, lightbulbs, electronics, and so on. Chlorine-containing chemicals within MSW are of particular concern, because their combustion can produce dioxins and furans, two groups of complex organic and toxic compounds.

WTE facilities are required to use air pollution control equipment to reduce the emissions of toxic chemicals. In 1995, under Section 129 of the Clean Air Act, the EPA adopted emissions guidelines for municipal waste combustors (MWCs). These regulations were fully implemented by 2000. The EPA reports in the fact sheet "Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Large Municipal Waste Combustors" (April 28, 2006, http://www.epa.gov/ttn/oarpg/t3/fact_sheets/largeMWC_fsfinal.html) that these limits substantially reduced MWC emissions of dioxins and furans (more than a 99% reduction), metals (more than a 93% reduction), and acid gases (more than a 91% reduction) compared with 1990s levels. In April 2006 the EPA adopted even tighter emission limits for the largest MWCs: those processing more than 250 tons of MSW per day.

FIGURE 6.10

focus on dioxins and furans

focus on dioxins and furans. In November 2006 the EPA released An Inventory of Sources and Environmental Releases of Dioxin-Like Compounds in the United States for the Years 1987, 1995, and 2000 (http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=159286). The report notes that MWCs were the largest single source of dioxin-like compounds in 1987, emitting 8,905 grams per year, or 64% of the total. (See Figure 6.11.) By 2000 these emissions had been substantially reduced to 84 grams per year, accounting for only 6% of total sources.

THE FEDERAL ROLE IN MSW MANAGEMENT

The federal government plays a key role in waste management. Its legislation has set landfill standards under the RCRA and incinerator and landfill emission standards under the Clean Air Act.

Some waste management laws have been controversial, resulting in legal challenges. Consequently, the federal government has also had an effect on waste management programs through federal court rulings. In a series of rulings, including Supreme Court decisions such as Chemical Waste Management v. Hunt, federal courts have held that shipments of waste are protected under the interstate commerce clause of the Constitution. As a result, state and local governments may not prohibit landfills from accepting waste from other states, nor may they impose fees on waste disposal that discriminate on the basis of origin.

Flow Control Laws

Municipalities nationwide have upgraded waste management programs and attempted to deal with public concern over waste issues. In most areas of the country state and local governments have played the lead role in transforming solid waste management. Private waste management firms have also been involved, often under contract or franchise agreements with local governments. Private firms manage most of the commercial waste and increasingly collect residential waste.

Flow control laws require private waste collectors to dispose of their waste in specific landfills. State and local governments institute these laws to guarantee that any new landfill they build will be used. This way, when they

FIGURE 6.11

sell bonds to get the money to build a new landfill, the bond purchasers will not worry that they will not be repaid. James E. McCarthy of the Congressional Research Service notes in "IB10002: Solid Waste Issues in the 106th Congress" (April 27, 2000, http://www.ncseonline.org/nle/crsreports/waste/waste-27.cfm) that "since 1980, about $10 billion in municipal bonds have been issued to pay for the construction of solid waste facilities. In many of these cases, flow control authority was used to guarantee the investment. Flow control also has benefited recycling facilities in cases where recycling was financed by fees collected at designated incinerators or landfills." In the process, however, a monopoly is created, prohibiting facilities outside a jurisdiction from offering competitive services. As a result, there have been a number of court challenges to flow control laws.

In 1994 the Supreme Court, in C & A Carbone v. Clarkstown (511 U.S. 383), held that flow control violates the interstate commerce clause. In response, however, many local governments have strongly pushed for the restoration of flow control authority. They have appealed to Congress, with its authority to regulate interstate commerce, to restore the use of flow control. As of September 2007, bills proposed to address flow control had failed.