Facility- and Subfacility-scale Assessment of Methane Emissions Inventory in the San Francisco Bay Area of California using Airborne Mass Balance
Abstract
The Bay Area Air Quality Management District (BAAQMD), the San Francisco Bay Area's (SFBA) air quality regulatory agency, has set a goal to reduce the region's greenhouse gas (GHG) emissions 80% below 1990 levels by 2050, consistent with California's climate goal. The BAAQMD maintains a regional `bottom-up' GHG emissions inventory derived using a combination of activity data and emission factors, in order to support the agency's climate action and rule-making programs, and to implement the control strategies laid out in the multi-pollutant 2017 Clean Air Plan.
Several top-down emissions assessment studies have used regional inverse modeling, methane (CH4) satellite column observations, airborne remote sensing imagery, and local enhancements of CH4 to consistently reveal an underestimation of CH4 emissions in California. Indeed, previous studies in the SFBA (Fairley and Fischer, 2015; Jeong et al., 2016) suggest that the measurement-based `top-down' regional CH4 emissions could be 1.3-2.3 times higher than the `bottom-up' inventory estimates. In order to reconcile this inconsistency, the BAAQMD conducted an airborne mass-balance based evaluation between 2016-19 that included 92 airborne observations collected over 23 facilities including 5 refineries, 10 landfills, 4 wastewater treatment plants (POTWs), 2 composting operations and 2 dairies in the SFBA (Guha et al., 2020). The average measured emissions for each refinery ranges from 4 to 23 times larger than corresponding bottom-up emissions reported to regulatory agencies, while measurement-derived landfill and POTW estimates are approximately twice the current inventory estimates. The observation-based CH4 emission estimates from composting operations, which was previously assumed to be insignificant, is similar in magnitude to total emissions from the POTW sector (~5% of the regional total).- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA102...08G
- Keywords:
-
- 0315 Biosphere/atmosphere interactions;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0322 Constituent sources and sinks;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES