California Air Resources Board

Principal Investigator/Author: Riley Duren

Contractor: University of Arizona

Contract Number: 20RD011

Project Status: Completed

Relevant CARB Programs: California Methane Research Program

Topic Areas: Climate Change, GHG Emission Inventory Program, Short-Lived Climate Pollutant Inventory, Mitigation

Executive Summary:

The University of Arizona (UA), with the support of their partners at Arizona State University (ASU) and NASA’s Jet Propulsion Laboratory (JPL), deployed the Global Airborne Observatory (GAO) to determine the locations and emission rates of methane (CH4) point sources1 in California. In addition to providing additional characterization of localized elevated CH4 emissions for the California Air Resources Board (CARB) and facility operators, this study served as a “dry run” for the Carbon Mapper satellite constellation that is currently being developed, with the first two launches planned for 2023. CARB is a key program partner and expressed interest in laying the groundwork for operational deployment of this technology towards quantifying and enabling the rapid mitigation of localized elevated CH4 emissions in California.

Following the same methods described in Duren et al. (2019), UA used airborne infrared imaging spectroscopy to survey priority areas and facilities in northern, central, and southern California. Priorities were established by CARB based on high emission sources observed during the previous California CH4 Survey in 2016-2017 and were also influenced by selected facility operators who indicated an interest in actively participating in this project. Researchers leveraged data analysis support from NASA’s JPL as part of their ongoing NASA-funded Carbon Monitoring System project that includes multi-scale CH4 analysis for California and other US states.

The campaign was conducted November 9 - 23, 2020. It included at least 3 complete surveys of all priority areas and 7 surveys of oil and gas operations in the southern San Joaquin Valley. In total, 56 facilities were surveyed, including 32 landfills and composting facilities, 6 power/cogeneration plants, 16 oil and gas facilities (production fields and gas compressor stations), and 2 wastewater treatment facilities.

Researchers identified 150 CH4 plumesattributed to 82 unique sources at 35 facilities with a total persistence-adjusted emission rate of 18,812 ±7,985 kilograms CH4 per hour (kgCH4/hr). No CH4 point source emissions above their detection limit of 5-10 kgCH4/hr were observed at 21 facilities. For the 43 facilities that were previously observed during the 2016-2017 California CH4 Survey, they estimate total, persistence-adjusted emissions of 17,507 ±7,489 kgCH4/hr in Fall 2020 or approximately 0.11 TgCH4/yr. This is 42% lower than CH4 emissions from the same facilities in 2016-2017, driven equally by similar reductions in the landfill and oil and gas sectors. Embedded in that net reduction were significant increases in localized high methane emissions activity at several facilities and a 20% overall growth in CH4 emissions from power plants surveyed in this study. The reasons for the observed net decrease are still being investigated, but there are initial indications that at least half of the decrease may be associated with mitigation efforts informed by data their team shared with operators following the original California CH4 Survey.

Quick-look plume geolocation products were delivered to CARB staff within several days of each flight, who in turn notified participating facility operators to support rapid follow-up and verification by ground teams. A summary of the feedback from industry provided to CARB, including whether or not an identified plume could be mitigated, and the reason for the emissions, is being prepared separately by CARB staff. Emission estimates with uncertainties were delivered to CARB to support assessments of point source emission distributions and to enable leak detection and repair efforts. CARB reported that several operators indicated cases where the data was used to support leak repairs. That list of repaired leaks is maintained by CARB and not included in this report. Subsequently, UA delivered refined image products and plume lists to CARB following manual quality control review. Additionally, on November 1, 2021, UA posted those data sets to the Carbon Mapper open data portal at https://carbonmapper.org/data/.

Keywords: methane (CH4), remote sensing, plume(s), airborne research, Carbon Mapper, methane emissions, landfills, ground-based sensors, database, emission sources, continuous measurements, satellite

Final Report: Please email research@arb.ca.gov to request the Final Report generated by this research contract.