CNG Is Clean

Emissions from a typical CNG vehicle are much lower than those from gasoline-powered vehicles. For example, the natural gas-powered Honda Civic GX is recognized by the U.S. EPA as the cleanest commercially available, internal-combustion vehicle. The Civic GX is rated by the California Air Resources Board as meeting the very stringent AT-PZEV standard.  

In addition, alternative fuel vehicles such as CNGs produce little or no evaporative emissions (i.e. fumes) during fueling and use. In gasoline vehicles, evaporative and fueling emissions can account for at least 50% of a vehicle's total hydrocarbon emissions.

Per unit of energy, natural gas contains less carbon than any other fossil fuel, and thus produces lower carbon dioxide (CO₂) emissions per vehicle mile traveled. While CNG vehicles do emit methane, another principle greenhouse gas, any increase in methane emissions is more than offset by a substantial reduction in CO₂ emissions compared to other fuels.

A recent study done on behalf of the California Energy Commission concludes that CNG vehicles produce up to 29% less greenhouse gas emissions than comparable gasoline vehicles and up to 22% less than comparable diesel vehicles. 

The bottom line is that natural gas-powered vehicles are dramatically better for the environment than gasoline-powered vehicles.

Source: NGVC.org: Environmental Benefits of Natural Gas Vehicles. 

“Vehicles (such as the Honda NGV) with a SULEV, PZEV or AT PZEV emissions rating emit only two pounds of hydrocarbons over 100,000 miles of driving – that's equivalent to spilling a pint of gasoline.”

- DriveClean.ca.gov