Issue 1, 2023

Likely substantial underestimation of reported methane emissions from United Kingdom upstream oil and gas activities

Abstract

The United Kingdom (UK) government's National Atmospheric Emissions Inventory (NAEI) is used to provide UK greenhouse gas emission data to the United Nations Framework Convention on Climate Change. The NAEI bottom-up approach estimated 2019 methane (CH4) emissions from the extraction and transport of oil and natural gas (O&G) from offshore sources to onshore terminals at 52 Gg CH4, corresponding to the loss of 0.14% of gas production. Here we investigate the approaches used by the NAEI and find it substantially underestimates leakage. We suggest alternative integrated approaches that combine direct measurements, management practices, and the effects of environmental conditions to estimate fugitive emissions. We estimate the total UK CH4 emissions from flaring, combustion, processing, venting, and O&G transfer to be 289 Gg CH4 (0.72% of production), five times larger than the NAEI estimate. We suggest NAEI underestimates emissions because of outdated/incorrect emission factors, incomplete activity data, and incomplete data on vented emissions. Similarly, CH4 emissions from upstream O&G in other countries may be underestimated, with regional regulatory differences resulting in venting often being a substantially underestimated emission source. While bottom-up methods can be used to understand the relative size of emissions from the extraction and transport of O&G, they are inherently biased low as they only include emissions from processes and activities designated as emission sources and for which emission factors exist. Emission factors remain a large source of uncertainty as many used to generate the NAEI inventory are taken from industrial studies or unpublished research that have not been independently validated. To improve the NAEI estimate, widespread and frequent direct measurements are needed to supplement and improve bottom-up emission estimates generated with existing emission factors and activity levels.

Graphical abstract: Likely substantial underestimation of reported methane emissions from United Kingdom upstream oil and gas activities

Supplementary files

Article information

Article type
Paper
Submitted
22 Sep 2022
Accepted
27 Oct 2022
First published
22 Dec 2022
This article is Open Access
Creative Commons BY license

Energy Environ. Sci., 2023,16, 295-304

Likely substantial underestimation of reported methane emissions from United Kingdom upstream oil and gas activities

S. N. Riddick and D. L. Mauzerall, Energy Environ. Sci., 2023, 16, 295 DOI: 10.1039/D2EE03072A

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