Waste Combustion
What is combustion?
Incinerators are specially designed furnaces for the combustion of municipal solid waste. Waste-to-energy facilities burn garbage and recover the heat energy for alternative uses such as generating electricity or steam. Incinerators without energy recovery simply burn garbage and allow the heat to escape to the atmosphere.
How many waste incinerators operate in America?
Of these, 86 waste-to-energy plants were operating in America in 2008, down from 102 in 2000. The Northeast has 40 of these plants, with 21 in the South, 1 in the South Central, 16 in the Midwest and 8 in the West.
Who owns these waste combustion systems?
The public sector and private companies each own half of the operating facilities.
How much garbage is combusted?
In 2008, 26 million tons, or 10.4 percent of America’s garbage, was incinerated. American waste-to-energy facilities have capacity to process more than 97,000 tons of municipal
solid waste per day. In most cases, the stated design capacity is greater than the actual amount of garbage burned, which is assumed to be 85 percent of rated capacity. The Northeast had the most waste-to-energy combustion capacity in 2008.
How much does it cost to dispose of trash in at an incinerator?
The average tipping fee at incinerators in the United States was $61.64 per ton in 2004. Average tipping fees for incinerators have risen steadily since 1982 when the average was $12.91 per ton. NSWMA’s tipping fee survey has more information.
How much electricity is produced by waste-to-energy facilities?
The nation’s waste-to-energy facilities have the capacity to generate the energy equivalent of 2,790 megawatt hours of electricity, including an electric generating capacity of 2,572 megawatts and an equivalent of 218 megawatts based on steam exports estimated at approximately 2.8 million pounds per hour, enough to power 1.6 million homes.
What remains after MSW is combusted?
When garbage is burned, ash is left on the combustion grates, much like ash is left on a fireplace. Ash is also extracted from the flue gases by air pollution control (APC) equipment. The combustion grate ash is called “bottom ash” and flue gas ash is called “fly ash”. Through the incineration process, the MSW volume is reduced by about 90 percent while the weight is reduced by about 75 percent (actual percentages will vary from facility to facility).
How are bottom ash and fly ash managed?
The two kinds of ash are usually managed together by the facility. Most is landfilled in MSW landfills or in monofills designed only to take ash. Some ash is reused for in road bed construction. Waste combustor ash is tested according to federal and state leaching standards (e.g., EPA’s toxicity characteristic leaching procedure test) and has consistently passed these tests.
Do waste-to-energy facilities cause air pollution?
No. Waste-to-energy facilities must achieve compliance with the air pollution requirements of the Clean Air Act Section 129. Waste-to-energy facilities employ sophisticated air pollution control equipment including:
- A bag house that works like a giant vacuum cleaner with filter bags that clean the air of soot (particulates), smoke, and metals;
- A scrubber that sprays a slurry of lime into the hot exhaust gas that neutralizes acid gases and improves the capture of certain metals (e.g., mercury);
- Selective non-catalytic reduction systems that convert nitrogen oxides (a cause of urban smog) to nitrogen by spraying ammonia into the hot flue gases; and
- Carbon injection systems that blow charcoal into the exhaust gases to sorb metals and control dioxin emissions.