Compressed Natural Gas (CNG)
To provide adequate driving range for a vehicle, CNG is stored in cylinders at a pressure of 3,000 to 3,600 pounds per square inch. A CNG-powered vehicle gets about the same fuel economy as a conventional gasoline vehicle on a gasoline gallon equivalent basis. A GGE equals about 5.66 pounds of CNG. CNG is used in light, medium and heavy-duty applications.
Liquefied Natural Gas (LNG)
LNG is produced by purifying natural gas and super-cooling it to -260°F to turn it into a liquid. Because it must be kept at cold temperatures, LNG is stored in double-walled, vacuum-insulated pressure vessels. LNG is good for trucks needing a longer range because liquid is more dense than gas (CNG) and, therefore, more energy can be stored by volume in a given tank. LNG is typically used in medium and heavy-duty vehicles; a GGE equals about 1.5 gallons of LNG.
Renewable Natural Gas (RNG)
Renewable natural gas (RNG) is a pipeline-quality gas that is fully interchangeable with conventional natural gas and thus can be used in natural gas vehicles. RNG is essentially biogas (the gaseous product of the decomposition of organic matter) that has been processed to purity standards. Like conventional natural gas, RNG can be used as a transportation fuel in the form of compressed natural gas (CNG) or liquefied natural gas (LNG).