Incineration is the burning of waste in a specially designed combustion chamber. The idea of burning garbage is not new, but with the increase in knowledge about toxic chemicals known to be released during burning, and with the increase in the amount of garbage to be burned, incineration now is done under controlled conditions. It has become the method of choice of many waste management companies and municipalities.

According to the Environmental Protection Agency (EPA), there are 135 operational waste combustion facilities in the United States. About 120 of them recover energy, and in all, the facilities process about 14.5% of the nation's 232 million tons (210.5 million metric tons) of municipal solid waste produced each year.

There are several types of combustion facilities in operation. At incinerators, mixed trash goes in one end unsorted, and it is all burned together. The resulting ash is typically placed in a...