CNG, LNG, Propane
Natural gas is a mixture of hydrocarbons, predominantly methane (CH4), it also contains hydrocarbons such as ethane and propane and other gases such as nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor. Natural gas has a high octane rating and excellent properties internal combustion engines. It is non-toxic, non-corrosive, and non-carcinogenic. It presents no threat to soil, surface water, or groundwater.
Natural gas accounts for approximately one quarter of the energy used in the United States. Of this, about one third goes to residential and commercial uses, one third to industrial uses, and one third to electric power production. Only about one tenth of one percent is currently used for transportation fuel.
Compressed Natural Gas (CNG)
Compressed natural gas, or CNG, is natural gas under pressure which remains clear, odorless, and non-corrosive. In 2003, California had over 1,200 natural gas centers operating. Well-extracted natural gas requires a cleanup process before it can be used in vehicles or residences. Using compressed natural gas as vehicle fuels increases energy security, paves the way for fuel cell vehicles, and improves public health and the environment.
Liquid Natural Gas (LNG)
Most natural gas consumed in the United States is domestically produced, with significant importation from Canada and a small but rapidly growing contribution from overseas imports in the form of liquefied natural gas (LNG). The vast majority of natural gas is a fossil fuel, formed over millions of years by the action of heat and pressure on organic material (ancient plants and animals). It is derived in much smaller amounts from renewable sources such as landfills and water/sewage treatment plants. To produce LNG, natural gas is purified and condensed into liquid by cooling; because it must be kept at such cold temperatures, LNG is stored in double-wall, vacuum-insulated pressure vessels. LNG fuel systems typically are only used with heavy-duty vehicles.
Propane
Propane is a by-product of natural gas processing and crude oil refining. It accounts for about 2% of the energy used in the United States. Propane is used to fuel home and water heating, cooking and refrigerating food, clothes drying, and powering industrial equipment. Rural areas that do not have natural gas service commonly rely on propane. Propane is safe fuel: propane tanks are 20 times more puncture resistant than gasoline tanks, and propane has the lowest flammability range of all alternative fuels. Compared with vehicles fueled by conventional diesel and gasoline, propane produces significantly lower amounts of some harmful emissions and the greenhouse gas carbon dioxide.
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