You can cook with it and heat your house with it. You may even power a car or truck with it. So what is it? ... natural gas. Like oil (petroleum), this common fuel comes from underground. However, natural gas, as the name implies, is a gas much like air, rather than a liquid like petroleum. It has been found to be one of the most environmentally friendly fuels, and its popularity is growing.
Natural gas is mostly made up of methane, about 95 percent of the natural gas in California. The other 5 percent is made up of various gases along with small amounts of water vapor. These other gases include butane, propane, ethane and other trace gases. Methane is a hydrocarbon, meaning its molecules are made up of hydrogen and carbon atoms. Its simple, one carbon, molecular structure (CH4) makes possible its nearly complete combustion.
2002 Crown Victoria - CNG Because of its clean burning nature and the fact that it is not made from petroleum, as gasoline and diesel are, many automakers around the world are developing vehicles to run on natural gas. Cars, vans, buses and small trucks generally use natural gas that has been compressed (called compressed natural gas or CNG) and stored in high-pressure cylinders.
Several vehicles are available today (such as the Honda Civic CGX above and the Ford Crown Victoria to the right) that operate on compressed natural gas. Some run on natural gas only and others can run on natural gas or gasoline (called bi-fuel vehicles).
i still think this doesnt answer ur question much.
Source :
http://www.energyquest.ca.gov/transportation/CNG.html