CNG stands for ‘Compressed Natural Gas’ and is mainly composed of methane. The natural gas is condensed to just 1% of its usual volume by passing it through a compressor. It remains in the form of a gas and is stored under high pressure in gas cylinders.
Natural gas can also be chilled and compressed further to improve fuel density and storage. This is known as High Density Compressed Natural Gas or HDCNG. Using HDCNG as a fuel means vehicles can drive longer distance and need to refuel less often.