Compressed Natural Gas (CNG) is a fossil fuel substitute for gasoline (petrol), diesel, or
propane fuel. It is a more environmentally clean alternative to those fuels, and it is much
safer than other fuels in the event of a spill (natural gas is lighter than air, and disperses
quickly when released).
CNG is made by compressing natural gas (which is mainly composed of methane [CH4]), to
less than 1% of its volume at standard atmospheric pressure. It is stored and distributed in
hard containers, at a normal pressure of 200–220 bar (2900–3200 psi), usually in cylindrical
or spherical shapes.
CNG is used in traditional gasoline internal combustion engine cars that have been converted
into bi-fuel vehicles (gasoline/CNG). Natural gas vehicles are increasingly used in Europe and
South America due to rising gasoline prices.
Compressed natural gas vehicles require a greater amount of space for fuel storage than
conventional gasoline power vehicles. Since it is a compressed gas, rather than a liquid like
gasoline, CNG takes up more space for each gasoline gallon equivalent (GGE). This problem
is solved in factory-built CNG vehicles that install the tanks under the body of the vehicle,
thanks to a more rational disposition of components, leaving the trunk free.
CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.