Incinerator is a furnace that burns waste materials to destroy them or reduce their volume. Incinerators range in size from household-refuse incinerators, frequently found in apartment buildings and businesses, to huge municipal (city) or industrial incinerators.
Large incinerators are used mainly to lessen the volume of material disposed of in landfills, where waste is deposited and covered with dirt. Many communities are running out of landfill space. Incinerators are also used to destroy harmful chemicals and disease-causing germs in certain types of waste materials.
There are four main categories of large incinerators, based on the type of waste material they burn: (1) hazardous waste (harmful chemical or metal waste) produced mainly as a by-product of industrial processes, (2) municipal waste, (3) medical waste, and (4) sewage sludge (muddy deposits). Industrial hazardous waste includes polluted wastewater, explosive or flammable substances, and other by-products contaminated with toxic substances. Municipal waste incinerators burn refuse collected by cities or waste-management businesses. Medical waste incinerators dispose of infectious waste and other burnable rubbish generated by hospitals. Sewage sludge incinerators burn sludge produced by plants that purify water from sewers and drains.
Large incinerators heat waste to up to 2000 °F (1100 °C), hot enough to break down toxic organic (carbon-containing) chemicals into less harmful gases and water. The heat also sterilizes infectious waste. Many newer incinerators use the heat from burning waste to produce steam, which then can be used to heat buildings or to generate electric power.
Many people oppose the use of incinerators because they can produce air pollution. The exhaust from incinerators contains gases and ash with small amounts of metals and other air pollutants. The exhaust may also contain small amounts of extremely toxic chemicals called dioxins. To help control pollution, newer incinerators often use scrubbers, devices containing chemicals that remove acid gases by soaking them. Also, cleaners called baghouses work like a large vacuum cleaner and catch particles of ash before they get to the incinerator stack. However, some critics say that the reduced amounts of pollutants released by newer incinerators are still unsafe.
The United States Environmental Protection Agency (EPA) sets standards for how much pollution can come out of an incinerator stack. The EPA also develops guidelines that states can use to determine whether to grant operating permits to incinerator owners.
