The gas also contains smaller amounts of volatile organic compounds, such as chlorinated and aromatic hydrocarbons.
Landfills are the largest source of human-caused methane emissions in the United States.
As waste decomposes in a landfill, it can generate gas for up to 30 years. Landfill gas poses environmental and safety hazards because the methane and volatile organic compounds contribute to air pollution and, under certain circumstances, can be explosive. It is also a source of odors if not flared or captured for commercial use. Environmental Protection Agency regulations now require landfill operators to collect the gases and burn off any that are not used for commercial purposes. Methane and CO2 were all that remained in the product gas.