Well-to-wheel analysis of direct and indirect use of natural gas in passenger vehicles

The abundance of natural gas in the United States because of the number of existing natural gas reserves and the recent advances in extracting unconventional reserves has been one of the main drivers for low natural gas prices. A question arises of what is the optimal use of natural gas as a transportation fuel. Is it more efficient to use natural gas in a stationary power application to generate electricity to charge electric vehicles, compress natural gas for onboard combustion in vehicles, or re-form natural gas into a denser transportation fuel? This study investigates the well-to-wheels energy use and greenhouse gas emissions from various natural gas to transportation fuel pathways and compares the results to conventional gasoline vehicles and electric vehicles using the US electrical generation mix. Specifically, natural gas vehicles running on compressed natural gas are compared against electric vehicles charged with electricity produced solely from natural gas combustion in stationary power plants. The results of the study show that the dependency on the combustion efficiency of natural gas in stationary power can outweigh the inherent efficiency of electric vehicles, thus highlighting the importance of examining energy use on a well-to-wheels basis. •Well-to-wheels analysis shows differences in use of natural gas for transportation.•Well-to-wheels approach needed to evaluate total energy use and greenhouse gas emissions.•Well-to-wheels energy and GHG (greenhouse gas) emissions depend on efficiency of the prime mover.•Efficiency of power generation critical for low GHG emissions with electric vehicles.•Fuel economy critical for low GHG emissions with compressed natural gas vehicles.