How waste-to-energy plants work
Waste-to-energy plants burn municipal solid waste (MSW), often called garbage or trash, to produce steam in a boiler, and the steam is used to power an electric generator turbine.
MSW is a mixture of energy-rich materials such as paper, plastics, yard waste, and products made from wood. For every 100 pounds of MSW in the United States, about 85 pounds can be burned as fuel to generate electricity. Waste-to-energy plants reduce 2,000 pounds of garbage to ash that weighs between 300 pounds and 600 pounds, and they reduce the volume of waste by about 87%.
The most common waste-to-energy system in the United States is the mass-burn system. In this system, unprocessed MSW is burned in a large incinerator with a boiler and a generator to produce electricity. A less common type of system processes MSW to remove noncombustible materials to produce refuse-derived fuel (RDF).
Generating electricity in a mass-burn waste-to-energy plant is a seven-step process:
- Waste is dumped from garbage trucks into a large pit.
- A giant claw on a crane grabs waste and dumps it into a combustion chamber.
- The waste (fuel) is burned, releasing heat.
- The heat turns water into steam in a boiler.
- The high-pressure steam turns the blades of a turbine generator to produce electricity.
- An air-pollution control system removes pollutants from the combustion gas before it is released through a smoke stack.
- Ash is collected from the boiler and the air-pollution control system.