Assessment of Regional Methane Emission Inventories through Airborne Quantification in the San Francisco Bay Area

Abstract

This study derives methane emission rates from 92 airborne observations collected over 23 facilities including refineries, 10 landfills, 4 wastewater treatment plants (POTWs), 2 composting operations and 2 dairies in the San Francisco Bay Area. Emission rates are measured using an airborne mass balance technique from a low-flying aircraft. Annual measurement-based sector-wide methane emissions are 19,000 ±2,300 Mg for refineries, 136,700 ±25,900 Mg for landfills, 11,900 ±1,500 Mg for POTWs, and 11,100 ±3,400 Mg for composting. The average of measured emissions for each refinery ranges from 4 to 23 times larger than corresponding emissions reported to regulatory agencies, while measurement-derived landfill and POTW estimates are approximately twice the current inventory estimates. Significant methane emissions at composting facilities indicate that a California mandate to divert organics from landfills to composting may not be an effective measure for mitigating methane emissions unless best management practices are instituted at composting facilities. Complementary evidence from airborne remote sensing imagery indicates atmospheric venting from refinery hydrogen plants, landfill working surfaces, composting stockpiles, etc., to be among the specific source types responsible for the observed discrepancies. This work highlights the value of multiple measurement approaches to accurately estimate facility-scale methane emissions and perform source attribution at sub-facility scales to guide and verify effective mitigation policy and action.

Robust Probabilities of Detection and Quantification Uncertainty for Aerial Methane Detection: Examples for Three Airborne Technologies

“…Methane-relevant studies have targeted measurements at an array of assorted facility types (Duren et al, 2019;Guha et al, 2020) with some focusing on oil and gas facilities (Cusworth et al, 2021;Frankenberg et al, 2016;Thorpe et al, 2020) solid waste facilities (Cusworth et al, 2020;Krautwurst et al, 2017), and arctic permafrost (Elder et al, 2020). In 2013, mounted the AVIRIS-NG instrument on a Twin Otter aircraft during controlled release experiments to evaluate methane retrieval algorithms and assess detection sensitivity as a function of wind speed and aircraft altitude.…”

Quantification and assessment of methane emissions from offshore oil and gas facilities on the Norwegian continental shelf

“…White et al, 1976;Wratt et al, 2001;O'Shea et al, 2014;Peischl et al, 2016;Pitt et al, 2019), as well as for individual O&G facilities (e.g. Lee et al, 2018;Guha et al, 2020).…”

Improved methane emission estimates using AVIRIS-NG and an Airborne Doppler Wind Lidar

“…Fig. D1 shows the second pass at the refinery on 20 Sept. with an observed CH 4 plume originating from a hydrogen plant (Guha et al, 2020). Wind speeds from HRRR and the BAAQMD tower were nearly identical at 3.3 to 3.4 m s − 1 .…”

“…A flight campaign in the Permian Basin identified 1100 CH 4 sources, with 50% of detected emissions resulting from oil and gas production, 38% from gathering and boosting, and 12% from processing (Cusworth et al, 2021). Additional studies have explored the underground gas storage (Thorpe et al, 2020) and waste management sectors (Krautwurst et al, 2017;Cusworth et al, 2020), sources in the San Francisco Bay area (Guha et al, 2020), and CH hotspots associated with thermokarst lakes (Elder et al, 2020).…”