Life Cycle Analysis of Natural Gas Supply Chain and End Use Applications in the United States.

Natural gas (NG) plays a crucial role in current and future energy systems in the United States due to its abundance and affordability. In this study a life cycle analysis of the NG supply chain in the United States was conducted using Argonne's R&D GREET model, examining stages from recovery to distribution using reported field data processed and documented by National Energy Technology Laboratory. Supply chain emissions were evaluated across multiple spatial scales, including national average, overall regional production, region-to-region, and basin-to-region scenarios. The GHG intensity of the U.S. average NG supply chain was estimated at 10.3 kg CO2e/MMBtu (lower heating value), with a range across regions from 7.8 kg CO2e/MMBtu (Northeast) to 15.1 kg CO2e/MMBtu (Pacific). The analysis further assessed how upstream NG emissions influence the life cycle GHG emissions of key end-use applications, including electricity generation (0.044-0.086 kg CO2e/kWh from upstream NG in combined cycle facilities), hydrogen production (1.04-2.20 kg CO2e/kg H2 for steam methane reforming [SMR] and 1.06-2.23 kg CO2e/kg for autothermal reforming [ATR]), and transit bus operation utilizing compressed natural gas fuel (0.19-0.37 kg CO2e/mile) and hydrogen fuel (0.12-0.25 kg CO2e/mile for hydrogen produced in SMR and ATR).