Compressed Natural Gas - CNG Compared To LNG

CNG Compared To LNG

Compressed Natural Gas is often confused with liquefied natural gas (LNG). While both are stored forms of natural gas, the key difference is that CNG is gas that is stored (as a gas) at high pressure, while LNG is stored at very low temperature, becoming liquid in the process. CNG has a lower cost of production and storage compared to LNG as it does not require an expensive cooling process and cryogenic tanks. CNG requires a much larger volume to store the same mass of gasoline or petrol and the use of very high pressures (3000 to 4000 psi, or 205 to 275 bar). As a consequence of this, LNG is often used for transporting natural gas over large distances, in ships, trains or pipelines, and the gas is then converted into CNG before distribution to the end user.

CNG can also be confused with LPG, which is liquified propane. Unlike natural gas (mostly methane), propane can be compressed to a liquid without continual refrigeration. LPG is commonly used to fuel vehicles in Australia.

CNG can be stored at lower pressure in a form known as an ANG (Adsorbed Natural Gas) tank, at 35 bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such as activated carbon and metal-organic frameworks (MOFs). The fuel is stored at similar or greater energy density than CNG. This means that vehicles can be refuelled from the natural gas network without extra gas compression, the fuel tanks can be slimmed down and made of lighter, weaker materials.