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

Area of Science:

• Environmental Science
• Chemical Engineering
• Energy Policy

Background:

• Regulatory and voluntary initiatives increasingly focus on estimating greenhouse gas (GHG) emission intensity for liquefied natural gas (LNG) supply chains.
• Activity-based national inventories often underestimate GHG emission intensities, highlighting the need for direct measurement data.

Purpose of the Study:

• To integrate measurement data into a life cycle assessment (LCA) framework for evaluating GHG emissions in LNG supply chains.
• To quantify the GHG emission intensity of LNG supply chains using a three-year measurement campaign.

Main Methods:

• Synthesized measurement data from 54 sites across production, midstream, and liquefaction stages.
• Applied a life cycle assessment (LCA) framework to integrate measurement data.
• Compared measurement-informed GHG emission intensities with activity-based inventory assessments.

Main Results:

• Measurement-informed GHG emission intensity ranged from 13.8 to 17.2 g CO2 equiv/MJ of LNG produced.
• This range is approximately 19-39% higher than estimates from activity-based inventory assessments.
• Stages downstream of gas production accounted for up to 73% of the production-to-liquefaction GHG emission intensity.

Conclusions:

• Relying solely on production-only emission intensities likely underestimates the total GHG impact of LNG.
• Downstream stages play a critical role in the overall GHG emission intensity of LNG supply chains.
• Supply chain-specific GHG intensity assessments, tied to individual transactions, are more accurate than basin-level estimates.