Author: Margaret Franklin, MSc, FICI, vice president, Institute of Chemistry of Ireland
Natural gas is a non-renewable fossil fuel, formed in a marine environment millions of years ago. It arose from the anaerobic decomposition of the remains of tiny marine organisms that died, sank to the sea floor and became trapped in sediments. Over millions of years, the sediments were compressed into sedimentary rocks, such as shale or sandstone.
Natural gas is composed mainly of methane (CH4), the least dense hydrocarbon. There may sometimes be traces of other hydrocarbons present, as well as contaminants such as hydrogen sulphide (H2S). If H2S is present, it needs to be removed before the gas is distributed. Methane cannot be liquefied at normal ambient temperatures and so cannot be bottled like propane or butane. It must be distributed by pipeline.