Airborne Methane Emission Measurements for Selected Oil and Gas Facilities Across California

Abstract

We report 65 individual measurements of methane emissions from 24 oil and gas facilities across California. Methane emission rates were estimated using in situ methane and wind velocity measurements from a small aircraft by a novel Gauss' Theorem flux integral approach. The estimates are compared with annual mean emissions reported to the U.S. Environmental Protection Agency (USEPA) and the California Air Resources Board (CARB) through their respective greenhouse gas reporting programs. The average emissions from 36 measurements of 10 gas storage facilities were within a factor of 2 of emissions reported to USEPA or CARB, though large variance was observed and the reporting database did not contain all of the facilities. In contrast, average emissions from 15 measurements of the three refineries were roughly an order of magnitude more than reported to the USEPA or CARB. The remaining measurements suggest compressor emissions are variable and perhaps slightly larger than reported, and emissions from one oil production facility were roughly concordant with a separate (not GHG reporting) bottom-up estimate from other work. Together, these results provide an initial facility-specific survey of methane emissions from California oil and natural gas infrastructure with observed variability suggesting the need for expanded measurements in the future.

Top‐Down Constraints on Methane Point Source Emissions From Animal Agriculture and Waste Based on New Airborne Measurements in the U.S. Upper Midwest

“…Figure illustrates the aircraft‐based point source quantification approach, which is described in detail by Conley et al () and briefly reviewed here—with additional information in the supporting information (USGS, ). The approach has been successfully used in many recent studies to quantify the magnitude and variability of point source methane emissions (Johnson et al, ; Lavoie et al, ; Mehrotra et al, ; Smith et al, ; Vaughn et al, ).…”

“…Major factors that can affect the accuracy of aircraft‐based point source flux estimates include instrumental uncertainty, weak or variable winds, shallow mixing depths (limiting the number of circuits that can be completed and increasing the extrapolated fraction below the lowest flight leg), and heterogeneity in the methane background (Gvakharia et al, ; Karion et al, ; Krings et al, ; Mehrotra et al, ; Ryoo et al, ). Here we estimate the overall top‐down flux uncertainty due to these factors from the variance in the measured methane enhancements and the precision of the wind and methane measurements, as described in the supporting information.…”

Evaluating Cropland N2O Emissions and Fertilizer Plant Greenhouse Gas Emissions With Airborne Observations

“…Emission rates from point sources are quantified following the methodology first described in Conley et al (2017) and used by Mehrotra et al (2017) and Vaughn et al (2017). Figure 2 illustrates the technique.…”

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

“…Airborne measurements, using an instrumented Mooney aircraft owned and operated by Scientific Aviation (Boulder, CO), were obtained at 23 facilities (92 flight observations) in the SFBA between 2015 and 2019. An example cylindrical flight path over a facility with colorcoded methane concentrations is shown in Figure S1 associated with this method are well-documented 25,26,28 and also summarized in the Supplementary Information (Appendix 1).…”