Natural gas plays a significant role in the global energy supply and also facilitates in achieving economic and environmental goals. Natural gas exists in forms of CNG (Compressed Natural Gas) and LNG (Liquefied Natural Gas) and has subtle differences.
Compressed Natural Gas
CNG is methane that is compressed to less than 1% of the volume that it occupies at a normal atmospheric pressure through a multi-stage process. It can be stored in high-pressure tanks 20-25 MPa (3,000-3,600 pounds per square inch). CNG is mostly used in buses and trucks and is a usable form of transportation fuel.
CNG is a lot cleaner than gasoline and diesel fuel, and is significantly inexpensive than gasoline, with the cost of natural gas going as low as $0.64 a GGE. CNG-powered vehicles emit lesser carbon monoxides and nitrogen oxides, which can be health hazards. On the downsides, CNG tanks require more storage space and have much lower energy density than liquid fuels.
Liquefied Natural Gas
LNG is also composed of methane like CNG, but it involves a more intricate cryogenic process, which facilitates cooling to a temperature of around -120 to -170 degrees Celsius. This process brings the natural gas to a liquid state at which it occupies around 1/600th of its gaseous state at a standard atmospheric pressure.
LNG is normally stored at atmospheric pressure in insulated double-walled tanks. Another novel way of storing is in a single-containment tank that has an earthen dam or dike, which acts as the secondary containment and also protects from any LNG spills. LNG has myriad mining, industrial, and transportation applications.
LNG in comparison to CNG offers an energy density that is comparable to petrol and diesel fuels. It is also very useful as gasification at a short notice is possible, unlike CNG. On the downside, it requires a major infrastructure for the LNG dispensing stations, transportation facilities, and production plants.
Both CNG and LNG will continue to play significant roles in today’s global economy.