Contribution of Regionalized Methane Emissions to Greenhouse Gas Intensity of Natural Gas-Fired Electricity and Carbon Capture in the United States

Natural gas is a fossil fuel primarily comprised of methane, a powerful greenhouse gas. As such, both combustion and direct atmospheric emissions of natural gas contribute to climate change. Natural gas supply chain methane emissions vary substantially based on extraction region and processes, such that natural gas end users experience very different lifecycle greenhouse gas intensities even for similar uses. Methane emissions have relevant implications for decarbonization pathways that use natural gas to generate electricity (with or without carbon capture) or remove carbon dioxide from the atmosphere. This Letter combines state-specific estimates of the methane emissions intensity of natural gas supplies with generator-level modeling to estimate the contribution of methane emissions to the greenhouse gas intensity of natural gas-fired electricity and carbon capture in the United States. For existing electricity generation, state-specific methane emissions factors are matched to individual natural gas-fired generators to estimate the [minimum, maximum] range for the carbon dioxide equivalent contribution of methane (100-year global warming potential = 29.8) relative to direct carbon dioxide emissions by balancing authority ([15%, 48%]), utility ([13%, 48%]), and the North American Electric Reliability Corporation region ([16%, 36%]). Methane emissions constrain the greenhouse gas avoidance or removal potential of natural-gas-fired carbon capture.