An evaluation of airborne mass balance and tracer correlation approaches to estimate site-level CH 4 emissions from LNG facilities using CO 2 as a tracer of opportunity

作者：Mark F. Lunt, Stephen J. Harris, Jörg Hacker, Ian Joynes, Tim Robertson, Simon Thompson, James L. France · 发表于：Atmospheric measurement techniques · 年份：2025 · DOI：10.5194/amt-18-4413-2025 · 被引用次数：3 · 研究领域：Atmospheric and Environmental Gas Dynamics、Atmospheric chemistry and aerosols、Oil, Gas, and Environmental Issues

Abstract. Accurate and representative quantification of methane (CH4) emissions from individual oil and gas facilities is crucial to improve our knowledge of CH4 sources, improve the reliability of emissions reporting and help facilitate mitigation opportunities. Liquefied Natural Gas (LNG) terminals primarily emit carbon dioxide (CO2) but are also potentially large CH4 sources in the gas supply chain. Here, in work supported by the United Nations Environment Program International Methane Emissions Observatory (UNEP's IMEO), we evaluate two airborne measurement approaches to quantify CH4 emissions from four LNG facilities. The first approach applies a downwind mass balance method to quantify emissions of both CH4 and CO2. Since operator-reported CO2 emissions are relatively well-established, we evaluate the method's performance by comparing to operator-reported CO2 values. Using this approach, we show that an individual facility CO2 mass balance quantification has a mean relative difference to operator reporting of ±20 %, with no significant mean bias across all estimates. The second approach uses measured CH4 : CO2 mole fraction ratios as an alternative method for estimating site-level CH4 emissions. Using this tracer correlation approach, we show that uncertainties in the ratio of CH4 : CO2 from a single day can be below ±10 % at the 95 % confidence level. Due to uncertainty in the CO2 emission rate, the resulting mean 2σ uncertainty on CH4 emissions is ±30 %. CH4 : CO2 rat...