Implications of Generation Efficiencies and Supply Chain Leaks for the Life Cycle Greenhouse Gas Emissions of Natural Gas-Fired Electricity in the United States

Uncertainties in supply chain emissions
raise questions about the
benefits of natural gas as a bridge fuel, but recent efficiency improvements
in gas-fired electricity generation remain overlooked. Our comprehensive
analysis of supply chain infrastructure and electricity generation
across the United States informs spatially and temporally resolved
estimates of life cycle greenhouse gas emissions. Results show decreasing
life cycle emissions over each year examined: 629, 574, and 525 kg
CO2 eq MWh–1 in 2005, 2010, and 2015,
respectively. Electricity generation contributed 86% of emissions
or greater for each year. Despite concerns over uncertain methane
leaks, efficiency improvements make it much more likely that natural
gas electricity has an unambiguous greenhouse gas benefit relative
to coal. Methane leaks would have to be 4.4 times the Environmental
Protection Agency (EPA) value in 2015 to reverse these benefits over
20-year time horizons. With retiring coal plants and scrutinized supply
chain emissions, our results show that natural gas can provide a lower
emissions option to coal in an increasingly decarbonized power sector.