Methane emissions from flaring at oil and gas wells are five times higher than was generally assumed by industry, according to a new study.
Methane is a potent greenhouse gas, with a global warming potential of between 27 and 30 times that of carbon dioxide.
The study indicates flaring — the process of burning off methane from gas and oil wells — is responsible for between 4 and 10 per cent of the US oil and gas industry's total methane emissions.
If the findings, which were calculated from oil and gas wells in the US and published on Friday in Science, translate internationally, it could indicate the fossil fuel industry has significantly underestimated global methane emissions.
Study co-author Eric Kort from the University of Michigan said it's been known for "more than a decade" that overall emissions from the US oil and gas industry were higher than reported, and his colleagues expected to see that was probably also the case for flaring.
"What we were less prepared to see was the high proportion of unlit flares simply venting methane to the atmosphere," Dr Kort said.
"Flares are a much larger contributor to those excess methane emissions than previously realised."
Flaring is done for a range of reasons.
For instance, exploratory gas wells that aren't connected to a processing facility flare their gas rather than pumping volatile methane straight into the air, and crude oil wells flare unwanted gas that sits on top of their underground oil reserves.
It's also used to manage pressure and volume in gas pipelines and facilities.
The higher the flaring efficiency — the amount of methane burnt off during flaring — the less methane enters the atmosphere from the flare.
Monitoring advances 'shifting power away from industry'
The industry-accepted figure for flaring efficiency is 98 per cent.
"If we consider just the US, if we addressed combustion issues such that the effective [conversion of methane] was 98 per cent, that would be approximately equivalent to removing 3 million cars from the road," Dr Kort said.
But, the researchers said, the assumption that flaring achieved 98 per cent efficiency was based on US Environmental Protection Agency studies from the 1980s, didn't account for unlit flares, and was not supported by real-world observations.
So they used aircraft to sample the emissions from flares across three US oil-and-gas basins, where more than 80 per cent of the country's flaring happens.
They combined that data with previous surveys that calculated the proportion of unlit flares.
They found that 91.1 per cent of methane was destroyed (converted) at each flare — about 7 per cent less than assumed — leaving almost 9 per cent of methane at each flare, on average, venting to the atmosphere.
The International Energy Agency (IEA) recently revised their estimate of flaring efficiency down to 92 per cent.
While Dr Kort said it wasn't clear what data the IEA used to settle on that figure, his team's results suggest that is a more accurate estimate than the industry assumption, and should be used globally in the absence of evidence to the contrary.
"[It] certainly would suggest that [IEA] number might align better with real-world flare performance than 98 per cent," he said.
"We haven't made measurements outside the US yet, but it would make sense to use the observation-based estimate from the US in the absence of better information."
Global satellite data used by the World Bank shows Australia was 31st by volume of flaring in 2020-21.
Dimitri Lafleur — a former Shell geoscientist — said he wouldn't be surprised if emissions from flaring are under-reported in Australia.
He also said flaring was likely to increase in Australia given our expanding gas industry.
"This is a study specific to the US ... [but] we are and have been very reliant on US standards," said Dr Lafleur, chief scientist at the Australasian Centre for Corporate Responsibility (ACCR).
In the past, emissions reporting has largely been done by industry, but Dr Lafleur said the use of aircraft in this study was an "exciting" development.
Using technology like aircraft and satellites is allowing independent researchers direct access to emissions data, and will make it harder for companies to underestimate their emissions, he said.
"The technology has already moved on and there are much better ways of empirically measuring what's going on.
"It's shifting power away from [industry], because it's giving independent experts the power to monitor their emissions."
Under-reporting compromises global emissions budget
According to Dr Lafleur, under-reporting of emissions is a widespread problem across the coal, oil and gas industry, and isn't limited to flaring.
Analysis from the ACCR earlier this year based on satellite data suggested Glencore was understating its fugitive methane emissions from its Australian coal mines by between 11 and 24 per cent.
Glencore had previously stated there was no reliable way to capture fugitive methane emissions during open-cut or surface mining, which includes the Hail Creek open-cut coal mine in central Queensland, and is known to emit significant volumes of methane.
And in another study using satellite data, geospatial analytics firm Kayrros reported last year that mines in the Bowen Basin emitted around 1.5 million tonnes of methane per year.
Australian government data showed only a third as much was reported for the same period.
Dr Lafleur said under-reporting emissions was a "big problem", and puts the world at risk of overshooting its emissions budget — how much CO2-equivalent gas we can emit before we overshoot 1.5C and more.
"If you don't know how much you have used, then you don't know how much you have left in [your budget].
"In a 1.5C-aligned world, the use of fossil fuels is ramping down very quickly."
In a statement in response to questions from the ABC, chief executive of the Australian Petroleum Production and Exploration Association (APPEA) Samantha McCulloch said the applicability of the study to an Australian context is "limited" given its US focus.
"In particular, it doesn't distinguish between oil and gas and so the greater presence of liquids in the US (which means flaring is more prevalent), along with the different age of the industry and its infrastructure, regulation and operations, means there are different factors at play," she said.
Ms McCulloch said the Australian industry was "committed to net zero by 2050" or sooner.
"The industry is committed to reduce flaring and continues to monitor, report and reduce its own emissions profile."
Although flaring "destroys" methane, the by-product of that is CO2 — another greenhouse gas.
Dr Lafleur said fossil fuels were no longer part of the energy mix of the future.
"Flaring is a necessary evil if you're talking about fossil fuel extraction and production, but in the longer term we need to be moving away from fossil fuels.
"There are plenty of other sources of energy. We know how efficient [renewables] are now."
