Burning
garbage has been a common means of disposal throughout history, but public
incinerators, then called cremators, became prevalent in America during the
1890s. By the 1920s, incineration had become one of the most common methods of
waste disposal in the United States. Land dumps and incineration alternated as
the preferred method of waste disposal from 1920-1970. In 1995, the EPA
estimated that 16 percent of municipal solid waste had been disposed off by some
form of combustion.
Incinerators
reduce the volume of waste by about 90 percent, a significant reduction of waste
that would otherwise go into a landfill. Incineration at high temperatures also
destroys many of the toxics and pathogens in medical and other hazardous wastes,
in addition to reducing the volume.
Thirty
to forty years ago, most incinerators were used simply to reduce the volume of
waste. Now, however, most incinerators in operation are waste-to-energy
facilities, which use the combustion process to generate steam and electricity.
Waste-to-energy
facilities can be either mass burn or refuse-derived-fuel facilities. In mass
burn facilities, wastes are indiscriminately injected into the boiler without
any preprocessing or sorting of noncombustible materials. These facilities burn
at temperatures of more than 1500 degrees and generally handle between 200 and
750 tons of municipal solid waste each day.
Refuse-derived
fuel (RDF) facilities, require that recyclable and non-combustible materials
such as glass and metals be sorted and removed so that fuel content is more
homogeneous and more energy is generated. These facilities are more costly to
build and operate so there are fewer RDF facilities in operation around the
world than traditional mass burn incinerators. In fact, most RDF facilities have
been commercial failures and some have been converted into mass burn facilities.
Waste-to-energy
facilities reduce the amount of waste going to landfills and the need to use
virgin fossil fuels. Considerable opposition, however, to waste incineration has
arisen. Concerns focus on their cost and fears about pollutants emitted in the
combustion process.
Resistance
to incinerators in many communities, however, has focused on potentially
hazardous emissions, such as dioxins (polychlorinated
dibenzodioxins) and furans (polychlorinated dibenzofurans), which can be
produced by the incomplete combustion of compounds containing chlorine, such as
polyvinyl chloride (PVC). Dioxins and furans can be formed as a result of
incomplete combustion (not everything is burned), they can result from burning
of certain materials, and they can be synthesized during cooling of incinerator
exhausts. It is not known what the relative contributions of each of these
processes are.