Evaluating carbon emissions reduction by use of natural gas as engine fuel

The exhaust emissions of carbon monoxide (CO) and carbon dioxide (CO₂) from a natural gas fuelled spark ignition engine have been evaluated. A production, four-cylinder, eight-valve, 1.4-l, flexible fuel engine equipped with a commercial natural gas kit was tested in a bench dynamometer. The tests were carried out simulating the standard emission test cycle U.S. FTP-75. The results demonstrate that natural gas substantially reduces exhaust CO emissions in comparison with gasoline, falling below current regulated limit even without use of catalytic converter. Use of natural gas also reduced CO₂ emissions to a level below the average of European fleet.