ABSTRACT
Natural gas is largely methane, CH4, a hydrocarbon found in its natural form which occurs in porous layers of the earth, often associated with or intermixed with oil or above the oil in a reservoir. Natural gas is often found in separate gas reservoirs. Ghengtu, Szechwan province, China, public buses with large flexible and inflatable bladders covering the roof area, hold a supply of natural gas for a prescribed route, using gas found near the city. In addition to being a convenient and available fuel, pollution problems are minimized. Liquid petroleum gas is primarily propane which, in contrast with natural gas, has the advantage that it can be liquefied by pressure at above freezing temperatures. Liquefied petroleum gas is produced from natural gas or from distillation of crude oil. Biological materials, either carbohydrate or lignocellulose, consist of carbon, oxygen and hydrogen, known as biomass, can be used as a resource to substitute for natural gas.
