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