Tracking U.S. Liquefied Natural Gas Supply Chain Greenhouse Gas Emissions Intensity through Direct Measurements

Recent regulatory and voluntary initiatives to estimate supply chain greenhouse gas (GHG) emissions intensity of liquefied natural gas (LNG) have emphasized the use of direct measurements as activity-based national inventories tend to systematically underestimate GHG emission intensities. In this work, we synthesize results from a three-year measurement campaign across production, midstream, and liquefaction stages into a life cycle assessment (LCA) framework to assess the GHG emissions intensity of U.S. LNG supply chains. Measurement-informed GHG emission intensity ranges from 13.8 – 17.2 gCO2e/MJ LNG produced, about 19-39% higher than those derived from an activity-based inventory assessment. We also observe large variation in the contribution of each stage to the total supply chain emission intensity. Critically, we find that stages downstream of gas production account for up to 73% of the production to liquefaction GHG emission intensity of LNG. Thus, relying on aggregate production-only emission intensities as the basis to assess the emissions impact of the LNG or gas placed in the destination market is likely to underestimate, leading to potentially ineffective public or corporate policies.