Technology – Compressed Natural Gas (CNG) & Liquefied Natural Gas (LNG)

5 05 2009

Advanced Fuels Technology – Natural Gas Vehicles

Compressed Natural Gas (CNG) is a fossil fuel substitute for gasoline (petrol), diesel, or propane fuel. Although its combustion does produce greenhouse gases, 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).

In most cases CNG and LNG engines are essentially the same – the key differences between the two applications is the way in which the fuel is stored on a vehicle.

Compressed Natural Gas, as the name implies, refers to gas which has been compressed to fit into specially designed high pressure storage cylinders. CNG is suitable for most classes of vehicles but generally requires more frequent refueling than liquid fuels. For this reason it is best suited for vehicles with ‘back-to-base’ operations or with easy access to CNG refueling equipment.

Liquefied Natural Gas is gas which has been cooled to -162 degrees Centigrade, at which point the gas becomes a liquid. LNG is stored in special cryogenic cylinders resembling a vacuum flask to retain the cold temperature. Liquefaction allows more fuel to be stored on board the vehicle.

LNG can be used for all classes of vehicle but is generally used in heavy vehicles which are used frequently (almost daily).


Conversion of your light or medium sized commercial vehicle to operate on natural gas could result in:

Fuel price savings – depending on your circumstances, fuel price savings in excess of 50% can be obtained.

Extended engine life – natural gas is inherently ‘clean’ and is proven to result in reduced engine wear

Reduced maintenance costs – In some circumstances, regular maintenance such as oil changes can be extended due to reduced wear and tear

Reduced emissions – Different applications produce different results but in general, natural gas engines produce lower particulate and NOx emissions. In some cases greenhouse gas savings can also be obtained, especially if you are using natural gas instead of petrol/gasoline.


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). Therefore, the tanks used to store the CNG usually take up additional space in the trunk of a car or bed of a pickup truck which runs on CNG. 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 a pathway to Hydrogen Vehicles technology

Though not specifically a natural gas vehicle, the relationship is such that natural gas vehicles are widely recognized as ‘the pathway to the hydrogen economy’.

Hydrogen vehicles can be driven by either internal combustion engines (ICE) or by fuel-cells. We have actively conducted research into hydrogen engine conversions and will remain at the forefront of the hydrogen vehicle industry in Australia




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