Waste to Energy
Waste-to-energy is considered a renewable because its fuel source—garbage—is sustainable and non-depletable – a “clean, reliable, renewable source of energy.”
The U.S. has 87 waste-to-energy plants nationwide that dispose of more than 90,000 tons of trash each day while generating enough clean energy to supply electricity to about 2.3 million homes nationwide.
Municipal waste consists of products that are combusted directly to produce heat and/or power and comprises wastes produced by the residential, commercial and public services sectors that are collected by local authorities for disposal in a central location. Hospital waste is included in this category.
The modern waste-to-energy plant turns garbage into energy using materials that range in size from the size of a pea to the size of a tree limb. The fuel can be wet or dry, and it varies greatly in energy content.
The process of producting energy from trash starts at the receiving building, where the trash is deposited onto the floor or into a large concrete pit. In many facilities, trash is then loaded directly into the furnaces. In other facilities, the trash is processed and shredded to produce a fuel before putting it into the boilers. Air for the combustion process in the furnaces is drawn from within the receiving building so that air is always flowing into the building from the outside. This creates a “negative pressure” within the building that prevents dust and odors from escaping the building.
The plant’s high temperature combustion furnace completely destroys viruses, bacteria, rotting food and other organic compounds found in household garbage that could potentially impact human health. The heat from the burning garbage boils water flowing inside the boiler tubes and turns the water into steam. The steam can be used directly in a heating system or a factory but it is usually used to turn a turbine-generator to make electricity. After any uncombustible residue (ash) cools, magnets and other mechanical devices pull metals from the ash for recycling. This is an important step, since a waste-to-energy plant can recycle thousands of tons of metals from its ash.
The Integrated Waste Services Association (IWSA) was formed in 1991 to promote integrated solutions to municipal solid waste management challenges. IWSA encourages the use of waste-to-energy technology as an integral component of a comprehensive, integrated solid waste management program.
- Waste-to-energy plants annually recover for recycling more than 700,000 tons of ferrous metals on-site. These facilities annually recycle more than 3 million tons of glass, metal, plastics, batteries, ash and yard waste. More than one-third of all ash is being reused as an aggregate material in roads and as landfill cover.
- Waste-to-energy technology prevents the emission of eleven million metric tons of greenhouse gases (methane and carbon dioxide) that would otherwise be released into the atmosphere on an annual basis.
- Waste-to-energy facilities today meet some of the most stringent environmental standards in the world and employ the most advanced emissions control equipment available including scrubbers to control acid gas, fabric filters to control particulate, selective non-catalytic reduction (SNCR) to control nitrogen oxides, and carbon injection to control mercury and organic emissions.
- Waste-to-energy serves as an alternative to land disposal and power generation from fossil fuels, which prevents the release of more than 20,000 tons of nitrogen oxides and 2.2 million tons of volatile organic compounds.
- Waste-to-energy reduces the volume of trash by about 90%, resulting in a 90% decrease in the amount of land required for garbage disposal.
Source: The Integrated Waste Services Association (IWSA)