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Alternative Fuels for Motor Vehicles

Compressed Natural Gas

Natural gas is typically found in underground deposits, often with petroleum, and is obtained by drilling. Natural gas is a mixture of hydrocarbons-mainly methane (CH4)-and is consumed in the residential, commercial, industrial, and utility markets.

To use natural gas, the methane component--which makes up 50 to 100 percent of natural gas--must be processed to remove contaminants as well as other useful fuels such as butane and propane.

For a vehicle to carry enough Compressed Natural Gas (CNG) to travel a reasonable distance, the gas has to be compressed to 3000 to 3600 psi. At 3600 psi, CNG has about one-third as much energy as gasoline and the tank must be far larger, heavier and more expensive than a conventional one. Something of a disadvantage you might say.

There are advantages to CNG from an environmental perspective because using CNG produces 90 percent less CO (Carbon Monoxide) and 60 percent less nitrogen oxides than its gas-powered counterpart. And, CO2 is reduced by 30 to 40 percent. Secondly because of the lower tax treatment of CNG compared with Gasoline the end product is much cheaper.

The disadvantages, apart from the tank problem, is cost of compressing the gas using electricity, the reality that the demand for natural gas is already high for other uses and the fact that it is not a renewable source coming, as it does, from the earth's natural petroleum reserves.

If it were to be used for powering cars and other vehicles then it would be a Dual-fuel or Flexible Fuel Vehicle, which would run on both standard Gasoline and CNG. This approach would require the re-tooling of the manufacturing process or an extensive retrofitting program.