Compressed Natural Gas
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 CNGpowered 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 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.