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Published April 2020 | Published
Journal Article Open

Methane emissions from underground gas storage in California


Accurate and timely detection, quantification, and attribution of methane emissions from Underground Gas Storage (UGS) facilities is essential for improving confidence in greenhouse gas inventories, enabling emission mitigation by facility operators, and supporting efforts to assess facility integrity and safety. We conducted multiple airborne surveys of the 12 active UGS facilities in California between January 2016 and November 2017 using advanced remote sensing and in situ observations of near-surface atmospheric methane (CH₄). These measurements where combined with wind data to derive spatially and temporally resolved methane emission estimates for California UGS facilities and key components with spatial resolutions as small as 1–3 m and revisit intervals ranging from minutes to months. The study spanned normal operations, malfunctions, and maintenance activity from multiple facilities including the active phase of the Aliso Canyon blowout incident in 2016 and subsequent return to injection operations in summer 2017. We estimate that the net annual methane emissions from the UGS sector in California averaged between 11.0 ± 3.8 GgCH₄ yr⁻¹ (remote sensing) and 12.3 ± 3.8 GgCH₄ yr⁻¹ (in situ). Net annual methane emissions for the 7 facilities that reported emissions in 2016 were estimated between 9.0 ± 3.2 GgCH₄ yr⁻¹ (remote sensing) and 9.5 ± 3.2 GgCH₄ yr⁻¹ (in situ), in both cases around 5 times higher than reported. The majority of methane emissions from UGS facilities in this study are likely dominated by anomalous activity: higher than expected compressor loss and leaking bypass isolation valves. Significant variability was observed at different time-scales: daily compressor duty-cycles and infrequent but large emissions from compressor station blow-downs. This observed variability made comparison of remote sensing and in situ observations challenging given measurements were derived largely at different times, however, improved agreement occurred when comparing simultaneous measurements. Temporal variability in emissions remains one of the most challenging aspects of UGS emissions quantification, underscoring the need for more systematic and persistent methane monitoring.

Additional Information

© 2020 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 12 September 2019; Accepted 11 February 2020; Accepted Manuscript online 11 February 2020; Published 1 April 2020. AVIRIS-C Aliso Canyon flights were funded by NASA Rapid Response and Novel research in Earth Science (Aliso Canyon RRNES project) and AVIRIS-NG flights over all facilities were funded by the California Air Resources Board, California Energy Commission, and NASA's Earth Science Division as part of the California Methane Survey. Additional project funding was provided through the NASA ACCESS (Methane Source Finder) and Carbon Monitoring System (CA Methane Prototype Monitoring System) programs. Work by MLF was supported by the California Energy Commission Public Interest Environmental Research Program and performed at the Lawrence Berkeley National Laboratory under US Department of Energy contract DE-AC02–36605CH11231. We would like to acknowledge the contributions of the AVIRIS flight and instrument teams, including Michael Eastwood and Winston Olson-Duval and South Coast Air Quality Management District personnel for their on-road methane surveys. Additional thanks to the Southern California Gas Company and Pacific Gas and Electric Company for their feedback in interpreting results. This work was undertaken in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Data availability: The data that support the findings of this study are openly available. AVIRIS-NG radiance products can be ordered from the AVIRIS-NG data portal at https://avirisng.jpl.nasa.gov/alt_locator/. Retrieved methane images from flight lines in this study are available for download at https://doi.org/10.3334/ORNLDAAC/1727 and images of methane plumes for California can be viewed at https://methane.jpl.nasa.gov/.

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Published - Thorpe_2020_Environ._Res._Lett._15_045005.pdf


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