Biogas, the gas that is emitted by decaying organic materials, can be refined into biomethane.  This product is considered on par with natural gas and can be used in the home or it can be compressed for use in cars that run on CNG.  So, a gas that starts as a biproduct of landfills and sewage plants can be used to power a part of America.  Right on!  Furthermore, a Natural Gas Vehicles For America article estimates that there is the potential to capture enough gas from existing sources to equal:

6% of all U.S. natural gas use

or

25% of all the diesel fuel used by all the buses and freight trucks in the U.S.

A natural gas is renewable, who’d a thunk it…

Here’s a particularly interesting excerpt from the same Natural Gas Vehicles For America website.

“In 2007, America used 22.9 trillion cubic feet (Tcf) of natural gas, which represented about 24 percent of all primary energy used in the U.S.  Of that amount, the 130,000 NGVs operating on U.S roads used no more than 0.052 percent!.  Even if the number of NGVs were to increase 100-fold in the next ten years to 11,000,000 or roughly 5 percent of the entire vehicle market (a formidable goal), the impact on natural gas supplies and the natural gas delivery infrastructure would be small — equating to about 4 percent of total U.S. natural gas consumption.”

CO