Natural gas is an odorless, nontoxic, gaseous mixture of hydrocarbons. It accounts for about a 25% of the energy used in the United States. About one-third goes to residential and commercial uses, such as heating and cooking; one-third to industrial uses; and one-third to electric power production.
To provide adequate driving range for a vehicle, Compressed Natural Gas (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.
There are three types of natural gas vehicles:
Dedicated: These vehicles are designed to run only on natural gas.
Bi-fuel: These vehicles have two separate fueling systems that enable them to run on either natural gas or gasoline.
Dual-fuel: These vehicles are traditionally limited to heavy-duty applications, have fuel systems that run on natural gas, and use diesel fuel for ignition assistance.
Currently, about 12-15% of public transit buses in the U.S. run on natural gas
Compressed and liquefied natural gas are clean, domestically produced alternative fuels. Using these fuels in natural gas vehicles increases energy security and can lower emissions. The driving range of non-gas vehicles is generally less than that of comparable gasoline and diesel vehicles because with natural gas, less overall energy content can be stored in the same size tank as the more energy-dense gasoline or diesel fuels.