Net greenhouse gas emissions savings from natural gas substitutions in vehicles, furnaces, and power plants
Cohan, Daniel S.
We compare the net greenhouse gas emissions impact of substituting natural gas for other fossil fuels for five purposes: light-duty vehicles, transit buses, residential heating, electricity generation, and export for electricity generation overseas. Emissions are evaluated on a fuel cycle basis, from production and transport of each fuel through end use combustion, based on recent conditions in the USA. To compare across sectors, the emissions difference between natural gas and its alternative is normalised by natural gas consumption to compute the net reduction in CO2e per MJ of natural gas used. Greatest emission reductions can be achieved by replacing existing coal-fired power plants (78gCO2-e/MJ natural gas) or fuel oil furnaces (66gCO2e/MJNG). Compressed natural gas in vehicles yields no significant reductions. Uncertainties arising from upstream emission rates for natural gas and the global warming potential of methane are quantified. The study demonstrates the critical role of deployment choice on the net climate impact of natural gas.