Biogas is made by the decomposition of organic matter, such as sewage, animal byproducts and solid waste from agricultural and other industries. The primary sources of biogas are landfills, livestock operations and wastewater treatment plants.
The main useful component of biogas is methane, which is produced during the digestion of organic matter in the absence of oxygen, along with carbon dioxide and trace gases such as hydrogen. Once it is cleaned, it can be used in the production of electricity or to power vehicles. The production of biogas in landfills takes place underground, and the landfill must be at least 40 feet deep to support it. It is only practical to collect biogas from landfills containing at least a million tons of waste. The biogas produced in landfills is mostly used for electricity generation.
Livestock operations, unlike landfills, require special digester containers to produce biogas. They mostly use animal manure. The biogas they produce is often used for vehicles. There is a much larger capacity to produce biogas in livestock operations than is currently used. Wastewater must be treated similarly to produce biogas, but is similarly underutilized. As of 2014, only about 1,500 wastewater treatment plants produce electricity, out of over 16,000 total.