For transportation applications, Natural Gas is a cost effective alternative to traditional fuels. Natural gas consists mostly of methane that when it is combusted is converted to carbon dioxide. The resulting carbon dioxide emissions from burning natural gas are up to 27% less than is produced from burning diesel fuel on an energy equivalent basis.
Most of the methane emissions associated with natural gas vehicles results from incomplete combustion and the release of unburnt methane. New natural gas engines deploy technology that improves efficiency and reduces unburnt methane emissions. The Cummins Westport Near-Zero Natural Gas engines are certified with a 14% reduction in CO2, and an overall 9% reduction in greenhouse gas emissions compared to their diesel counterpart (using GWP100 from IPCC AR4), and a 70% methane emission reduction compared to similar natural gas engines produced only a few years ago.