Collecting and using biogas from landfills
Landfills for municipal solid waste can be a source of energy. Anaerobic bacteria—bacteria that can live without the presence of free oxygen—living in landfills decompose organic waste to produce a gas called biogas. Landfill biogas is 40%–60% methane. The rest is mostly carbon dioxide (CO2) and small amounts of other gases. Methane is the same energy-rich compound—CH4—found in natural gas, which we use for heating, cooking, and producing electricity.
Biogas with high methane content can be dangerous to people and the environment because methane is flammable. It is also a strong greenhouse gas. In the United States, regulations under the Clean Air Act require landfills of a certain size to install and operate a landfill gas collection and control system.
Some landfills reduce methane gas emissions simply by burning—or flaring—the methane gas. Burning methane produces CO2, but CO2 is not as strong a greenhouse gas as methane. Many landfills collect biogas, treat it, and then sell the methane. Some landfills use the methane gas to generate electricity.
The U.S. Energy Information Administration (EIA) estimates that in 2016, about 278 billion cubic feet of landfill gas was burned for energy at U.S. landfills, 99% of which was used to generate about 11.2 billion kilowatthours (kWh) of electricity, or about 0.3% of total U.S. electricity generation in 2016.
Using biogas from animal waste
Some farmers produce biogas in large tanks called digesters, where they put manure and used bedding material from their barns. Some farmers cover their manure ponds (also called lagoons) to capture biogas. Biogas digesters and manure ponds contain the same anaerobic bacteria found in landfills. The methane in the biogas can be burned to heat water and buildings and for fuel in diesel-engine generators to generate electricity for the farm.