CNG

Fuel that is gaining increasing use as an alternative to petroleum for vehicles. It consists of natural gas, which is largely methane, stored at over 200 times atmospheric pressure in spheres or cylinders.

Vehicles can be refuelled at special CNG filling stations or, in some countries, can be refuelled in homes equipped with a natural-gas supply. Among CNG's advantages are its cheapness, relative safety (being lighter than air, the gas rapidly disperses if there is a leak), and lower harmful emissions. CNG has been adopted in the public transport systems of many cities in Asia and South America.