It is often found in conjunction with petroleum deposits. Before it is distributed, natural gas usually undergoes some sort of processing. Non-hydrocarbon gases, such as hydrogen sulfide, must also be removed. The cleaned gas is then distributed throughout the country through thousands of miles of pipeline. Local utility companies add an odorant before delivering the gas to their customers.
Some methane is manufactured by the distillation of coal.
Coal is a combustible rock formed from the remains of decayed vegetation. It is the only rock containing significant amounts of carbon. Coal also contains hydrogen and oxygen, with small concentrations of nitrogen, chlorine, sulfur, and several metals. Substances released from bituminous coal when it is distilled, in addition to methane, include water, carbon dioxide, ammonia, benzene, toluene, naphthalene, and anthracene. In addition, the distillation also yields oils, tars, and sulfur-containing products.