Landfill Gas Methane is the most abundant organic chemical in the Earth's atmosphere. While 75 per cent of methane in the atmosphere is naturally occurring and therefore difficult to control, landfills are responsible for 25 per cent of the controllable methane sources. Gas production rates from a landfill vary depending on garbage composition, moisture content, temperature and methane partial pressure. Gas production cannot be halted or contained as it gradually percolates through the garbage and escapes to the atmosphere by the path of least resistance. Problems can therefore arise if the issuing gas is not carefully controlled or flared.
Gas can even migrate and accumulate in nearby buildings, increasing the risk of explosion.
Completed landfill sites are usually made into golf courses or parks for safety reasons although escaping gas can still destroy grass and trees. The composition of garbage in a landfill varies depending on the cultural habits of the society filling it. Typical contents are food and garden waste, paper products, plastics, rubber, textiles, wood and inert materials. These ingredients generate different quantities of methane due to differing chemical characteristics. In recent years, as environmental awareness has increased, the relative quantity of recyclable materials and heavy metals has declined significantly.