Gas Pathing: Improved Greenhouse Gas Emission Estimates of Liquefied Natural Gas Exports through Enhanced Supply Chain Resolution

The utilization of greenhouse gas (GHG) life cycle assessments (LCAs) of liquefied natural gas (LNG) has increased over the past decade. In this study, a novel framework for improved supply chain-specific LCAs for GHGs is presented using a gas pathing algorithm aligned with how gas is purchased, sold, and transported within the U.S. Utilizing supply chain emissions and gas purchase data specific to two U.S. liquefaction facilities, we identify 138 distinct gas pathways with GHG emission profiles that can vary by nearly a factor of 6. Reference case GHG intensities are 22-53% lower than prior studies for U.S. LNG delivered to Europe (production through regasification, 100-yr GWP). This study also incorporates recent supply chain measurement data. GHG intensities based on measurement data for U.S. LNG delivered to Europe are 41-52% higher than the reference case (production through regasification 100-yr GWP) and 8-11% higher for production through power generation boundaries (all market destinations, 100-yr GWP) but 20-28% lower than prior estimates employing national or regional nonempirical data. Supply chain-specific LCAs and the integration of emission measurements in LCAs are critical to accurately characterize the differences in GHG emissions from natural gas and LNG supply chains.