The City of Commerce Refuse-to-Energy incinerator was built in 1986 and is operated by the Sanitation District of Los Angeles County. It burns 400 tons of trash per day and produces 10 megawatts of electricity, enough for 20,000 homes. Supporters of incinerators propose that waste that can not be recycled or landfilled, might be burned for energy. Two controversial issues involving incinerators are how safe are the exhaust gases, and should the burned trash be classified at "recycled" material.
Trash is burned at high temperature to reduce pollutants. Water is boiled to turn a turbine and generate electricity.
Trash trucks drive about 10-15 miles to the Commerce plant. The waste is dumped into a large pit and then lifted up with a mechanical claw and dumped into the furnace.
Most of the trash comes from commercial sources. Hazardous waste is not accepted. A truck caught carrying hazardous waste will not be allowed back. The pit that collects the trash is big enough to hold three days of trash (fuel). This means the plant can operate 24 hours per day, 7 days a week. In order to keep the odors from the trash trucks from reaching the neighborhood, the pressure inside the receiving area is kept low so that the odors do not escape the collection area.
The challenge to operating an incinerator-power plant is to controll the burn temperature so that it is high enough to prevent the creation of dioxin from plastics, and low enough so that not too many nitrogen oxides are produced. A camera and temperature sensors are placed in the incinerator so that an operator can keep the temperature close to 1,800 F. The plant operator watches the sensors to control the conditions in the furnace. The plant has actually burned nothing but plastic on some days and not violated dioxin pollution standards.
Water is super-heated by the furnace to produce high pressure and spin a turbine. The turbine turns a generator to generate the 10 megawatts of electricity. THe electricit is sold to the local utility company. About 60%-70% of the revenue comes from selling electricity. About 40% of the plant was built to generate electricity, and about 60% is devoted to air quality equipment. Other steps to reduce pollution include injecting ammonia during combustion to produce more N2 gas (which naturally makes up 78% of the atmosphere) and less nitrogen oxides (NOx) which produce the brownish haze air pollution. Also, fly ash (lime) is injected as a powder which collects acid gases and NOx. The fly ash and acid gas particles drop into a collection chamber.
The S.E.R.F. incinerator in Long Beach on Terminal Island burns 1,500 tons per day and also produces electricity.
The final step moves the combustion gas into the bag house, which is a collection of gortex bags and lime to filter gases.
The final products from the burning of refuse are waste ash and exhaust gases. The waste ash is added to cement (left) and used as road bed at a local landfill. Concrete chemically bonds with the metals and waste to bond and seal it permanently. The exhaust gases and water vapor are seen leaving the smoke stack (right).
Part of the agreement for building the incincerator was that it would only accept City of Commerce trash and only charge $35 per ton. It is expected that as inexpensive landfills close in Los Angeles County, that landfill disposal rates will rise to $80 per ton in coming years.
Do Incinerators create too much air pollution? Residents in South Central Los Angeles defeated the L.A.N.C.E.R. incinerator because they felt not enough studies had been done on the health hazards. Proponents of incinerators claim that all pollution is monitored at the smoke stack and that they have to meet strict standards set by the South Coast Air Quality Management District (AQMD).
Some state legislators have also tried to classify burned trash as recycled trash in an effort to meet the 50% recycling goal for the year 2,000. Environmental groups such as Californians Against Waste (C.A.W.) argue that burned paper and plastic are not recycled (post consumer) since they are not turned back into new products.
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