16. How is methane produced when garbage is put into a landfill?

According to the US Environmental Protection Agency, about 23% of the methane released in the US every year comes from landfills. This is the second largest human related source of methane (natural gas and petroleum production systems are the largest source).

Methane is generated in landfills as organic matter decomposes without the presence of oxygen (anaerobic conditions). The amount of methane created depends on the quantity and moisture content of the waste and the design and management practices at the site. However, as a general rule of thumb one tonne of methane is produced from every tonne of municipal waste put into landfills.