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Waste-to-Energy (Municipal Solid Waste)

Energy from municipal solid waste

Municipal solid waste (MSW), often called garbage, is used to produce energy at waste-to-energy plants and at landfills in the United States. MSW contains

  • biomass, or biogenic (plant or animal products), materials such as paper, cardboard, food waste, grass clippings, leaves, wood, leather products
  • nonbiomass combustible materials such as plastics and other synthetic materials made from petroleum
  • noncombustible materials such as glass and metals

In 2014, about 258 million tons of MSW were generated in the United States, of which

  • 53% was landfilled
  • 35% was recycled and composted
  • 13% was burned for energy

Waste-to-energy plants make steam and electricity

MSW is usually burned at special waste-to-energy plants that use the heat from the fire to make steam for generating electricity or to heat buildings. In 2015, 71 waste-to-energy power plants and four other power plants burned MSW in the United States. These plants burned about 29 million tons of MSW in 2015 and generated nearly 14 billion kilowatthours of electricity. The biomass materials in the MSW that were burned in these power plants accounted for about 64% of the weight of the MSW and contributed about 51% of the energy. The remainder of the MSW was nonbiomass combustible material, mainly plastics. Many large landfills also generate electricity by using the methane gas that is produced from decomposing biomass in landfills.

Waste-to-energy is a waste management option

Producing electricity is only one reason to burn MSW. Burning waste also reduces the amount of material that would probably be buried in landfills. Burning MSW reduces the volume of waste by about 87%.

Last updated: March 20, 2017

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 that is used to generate electricity.

There are different types of waste-to-energy systems or technologies. The most common type used in the United States is the mass-burn system, where unprocessed MSW is burned in a large incinerator with a boiler and a generator for producing electricity (see illustration below). Another, less common type of system processes MSW into fuel pellets that can be used in smaller power plants.

image showing how a mass burn waste-to-energy plant work

Source: Adapted with permission from Deltaway Energy

The process of generating electricity in a mass-burn waste-to-energy plant has seven stages:

  1. Waste is dumped from garbage trucks into a large pit.
  2. A giant claw on a crane grabs waste and dumps it in a combustion chamber.
  3. The waste (fuel) is burned, releasing heat.
  4. The heat turns water into steam in a boiler.
  5. The high-pressure steam turns the blades of a turbine generator to produce electricity.
  6. An air pollution control system removes pollutants from the combustion gas before it is released through a smoke stack.
  7. Ash is collected from the boiler and the air pollution control system.

Think of municipal solid waste as a mixture of energy-rich fuels. For every 100 pounds of MSW in the United States, more than 85 pounds can be burned as fuel to generate electricity. Those fuels include paper, plastics, and yard waste. In 2016, one ton of MSW burned in waste-to-energy plants in the United States generated about 474 kilowatthours (kWh) of electricity, the amount of electricity used by about 16 U.S. households in one day.

In a waste-to-energy plant, 2,000 pounds (one ton) of garbage is reduced to 300 pounds–600 pounds of ash.

Trash burned around the world

Many countries use waste-to-energy plants to capture the energy in waste. The use of waste-to-energy plants in some European countries and Japan is relatively high, in part because those countries have little open space for landfills, and they have few energy resources.

Last updated: January 24, 2018