20th Century was Century of Oil; 21st Century would be the Century of Natural Gas!
Oil and its product are used as the main sources of energy for about last one and half centuries through they dominated basically the twentieth century.
It is supplied for household use as LPG (Liquefied petroleum Gas) and also used for running vehicles as CNG (Compressed Natural Gas). It is obtained from shrubs, farm wastes, animal and human wastes.
The gaseous mixture of lower hydrocarbons which occurs deep inside the earth either alone or covering the crude oil in an oilfield is called natural gas. Natural gas mainly (90%) consists of methane (CH4).