Emissions
Natural gas burns cleaner than conventional gasoline or diesel due to its lowercarbon content. When used as a vehicle fuel, it can offer life cycle greenhouse gas (GHG) emissions benefits over conventional fuels, depending on vehicle type, drive cycle, and engine calibration. In addition, using natural gas may reduce some types of tailpipe emissions.
Tailpipe emissions result from fuel combustion in a vehicle's engine and are emitted from its exhaust system. The emissions of primary concern include the regulated emissions of hydrocarbons, oxides of nitrogen (NOx), carbon monoxide (CO), as well as carbon dioxide (CO2). Due to increasingly stringent emissions regulations, the gap between tailpipe emissions benefits from natural gas vehicles (NGVs) and conventional vehicles with modern emissions controls has narrowed. That's because the U.S. Environmental Protection Agency (EPA) is holding all fuels and vehicle types accountable to the same levels of air pollutants emitted from vehicle combustion. Still, NGVs continue to provide emissions benefits—especially when replacing older conventional vehicles or when considering life cycle emissions.