Carbon Intensity of United States Natural Gas Supply

Understanding greenhouse gas (GHG) emissions from natural gas systems is essential for transitioning to a low-carbon economy. This work estimates well-through-transmission GHG emissions of the US natural gas from one million wells covering 91% production in 2023. A high-resolution US oil and gas production area map is developed to harmonize spatial and tabular data from the oil and natural gas (O&NG) supply chain. We systematically integrate latest aerial campaign measurement into natural gas life cycle GHG emission estimates, capturing methane fugitives with better characterization of superemitter events. More than ten public and commercial data sets are integrated with an engineering-based unit process life cycle assessment (LCA) model. The estimated total GHG emissions from the US gas sector are 719 MMT CO2eq, more than twice the estimates of the US Environmental Protection Agency. The average well-through-transmission carbon intensity (CI) for US natural gas is 15.99 [15.14, 16.90] gCO2eq/MJ, with an upstream (exploration through processing) CI of 12.27 [11.84, 12.68] gCO2eq/MJ and a midstream (transmission) CI of 3.72 [3.30, 4.22] gCO2eq/MJ (bracketed values indicate uncertainty ranges). Methane fugitive and venting account for 61% and 21% of the upstream CI, an order of magnitude higher than flaring contributions (2.1%). Reducing methane fugitive and venting loss rates by 75% would reduce the upstream CI by half.