8,000 -7,000 -6,000 -5,000 -4,000 -3,000 -2,000 -1,000 -
1989 1990 1991 1992 1993 1994
1996 1997 19
source: "Figure 5. Number of Landfills in the United States by Year," in Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2003, U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC, April 2005, http:// www.epa.gov/epaoswer/non-hw/muncpl/pubs/msw05rpt.pdf (accessed June 22, 2005)
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.
Illegal dumping is a continuing problem. One major reason for illegal dumping is the cost of legally disposing of waste in landfills. In addition, the declining number of landfills, with those remaining often sited at a distance, has led to increased illegal dumping. Illegal dumping endangers human health and the environment because the dump sites become breeding grounds for animal and insect pests, present safety hazards for children, are sources of pollutants, and disrupt wildlife habitats.
Incineration and combustion both include heating MSW to very high temperatures. In the past MSW was burned in incinerators primarily to reduce its volume. During the 1980s technology was developed that allowed MSW to be burned for energy recovery. Use of MSW as a fuel is more commonly termed combustion; however, both terms are used interchangeably. The EPA refers to MSW combustion as a waste-to-energy (WTE) process.
In 2003 approximately thirty-three million tons of MSW were incinerated, representing 14% of the total MSW generated that year. (See Figure 6.8.) The EPA estimates that combusting MSW reduces the amount of waste by up to 90% in volume and by up to 75% in weight. As of fall 2004 there were eighty-nine WTE facilities operating in the United States generating approximately 2,500 megawatts of power.
Figure 6.12 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 very 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.
According to the Rubber Manufacturers Association, 104 million scrap tires were burned as fuel during 2003 in specialized facilities. As shown in Table 6.7, tires have a very high average heat content compared to typical MSW.
Some experts think that incinerators are the best alternatives to landfills, while others believe that they are good additions to landfills. WTE facilities do provide an alternative energy source to traditional fossil fuels, and the sale of the energy they produce helps offset the cost of operating the facilities. Incinerators are very expensive to build.
According to the Department of Energy (DOE), in 2003 waste-derived energy comprised just over one-half of 1% of the nation's total energy supply, producing 558 trillion British thermal units (BTUs) of power. (See Figure 6.13.) The DOE hopes to increase this value to 2% by the year 2010.
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