Coal gas / syngas is obtained by destructive distillation of coal. It is a mixture of hydrogen (50%), Methane (35%), carbon monoxide (10%), Ethylene (5%) and other volatile hydrocarbons, carbon dioxide and nitrogen. Before natural gas became popular in 1940s and 1950s, Coal gas was the primary source of gaseous fuel for the United States and the UK. It was used for lighting, cooking, and heating and was often supplied to households via a municipally owned piped distribution system.