UK substantially underestimates its methane emissions from oil and gas production -- and many other countries probably do too

Methane is the second most important greenhouse gas after carbon dioxide, contributing about 1 degree Fahrenheit of present-day global warming relative to pre-industrial times. One major source of methane to the atmosphere is the extraction and transport of oil and gas. Countries are obligated to report their greenhouse gas emissions to international bodies such as the United Nations Framework Convention on Climate Change, but recent studies suggest that the current methods for calculating methane emissions rely on outdated and incomplete information and may not accurately represent actual emissions.

A recent study from researchers at Princeton University and Colorado State University finds that the current method for estimating methane emissions from offshore oil and gas production in the United Kingdom systematically and severely underestimates emissions. The study finds that as much as five times more methane is being emitted from oil and gas production in the UK than what the government has reported. The researchers reached this conclusion by critically evaluating the UK's current method of calculating methane emissions, suggesting alternative, peer-review based methods and generating revised emission estimates.

Sincemany other countries use similar methodologies to calculate methane emissions from oil and gas production, this severe underestimation is likely not confined to the UK alone.

"It is critical to know when, where and how much methane is emitted from each of its sources in order to prioritize emission reductions," said Denise Mauzerall, a co-author and core faculty member of the Center for Policy Research on Energy and the Environment at Princeton University. "We hope our work will facilitate improved emission estimates and reductions not only from the UK but also from other countries producing methane from oil and gas extraction," Mauzerall said.

Due to its climate and indirect health impacts (methane is a precursor for ozone which is an air pollutant that damages human health and crops), methane mitigation has recently become a global policy priority. Its relatively short lifetime of about 12 years and high heat trapping ability per molecule makes reducing methane emissions among the most effective ways to slow the rate of climate warming. As a result, in 2021 countries signed the Global Methane Pledge, committing to reduce methane emissions by at least 30% of 2020 levels by 2030. To track progress, countries compile national emissions data into inventories, such as the UK's National Atmospheric Emissions Inventory (NAEI), which are then reported to international monitoring bodies.

This study focuses on methane leakage associated with discovery, extraction, and production of oil and natural gas. These methane emissions are typically calculated by multiplying the activity level of various processes - namely venting, flaring, processing and combustion activities on production platforms, offshore oil loading, and gas transfer by high-pressure pipelines - by "emission factors," which are standard estimates of the methane emissions associated with each activity.

The researchers found that the emissions factors used in the UK's reporting are either outdated, rely on unpublished or publicly unavailable industry research, or use generic values recommended by the IPCC. Furthermore, these emission factors are usually "static," meaning that they are not sensitive to factors such as environmental conditions and management practices which could affect emissions from various processes. In addition, leakage can occur when the off-shore rigs are idle - an "activity" that does not currently have an associated emission factor.

Noting these shortcomings, the researchers updated and revised estimation techniques for each process, and, wherever possible, used dynamic rather than static emission factor formulations that account for varying environmental conditions. They also incorporated direct boat-based measurements of methane concentrations around offshore gas platforms in the North Sea collected in summer 2017, documented in a study also led by the authors. These updates resulted in a total methane emission estimate more than five times larger than reported emissions.

"Methane emissions from offshore facilities are currently largely uncertain, and because sources on facilities only emit for a short time period, using direct survey methods such as satellite or drones will probably only capture about 25% of the actual emissions," said Stuart Riddick, lead author and research scientist at Colorado State University. "To generate representative baseline emissions across the sector, we need to work with industry to develop practical, effective, and collaborative measurement strategies," Riddick said.

Previous research has shown that reducing leakage across the oil and natural gas supply chain can advance climate and air quality goals while also being economically profitable - a win-win opportunity for industry and climate.

This study adds to a growing base of literature finding that current measurements of anthropogenic methane emission inventories are too low. With the world's first "global stocktake" on progress implementing the Paris Agreement concluding in 2023, the researchers argue that improved measurement of emissions deserves urgent attention.

"We are hopeful that our work will facilitate more accurate emission inventory development and lead to critically important reductions of methane leakage - a win for both industry and the environment," Mauzerall said.