Australian expert panel says satellite and aircraft data could reshape coal mine methane estimates

An interim report by an Australian expert panel has concluded that atmospheric measurement techniques — sensors mounted on satellites, aircraft, drones and ground stations — could materially improve how the country estimates fugitive methane emissions, with coal mining the sector where the gap between reported and measured volumes is most disputed. The findings were reported by Renew Economy.

What the panel was asked to examine

The panel, led by former Chief Scientist Cathy Foley, was charged with studying whether new atmospheric measurement approaches could further enhance Australia's fugitive methane estimates. The report notes there is growing interest in new ways to detect and quantify methane in the atmosphere, and states that such “top-down” approaches may improve how Australia estimates fugitive emissions, adding that cutting methane emissions can help slow climate change in the near term.

The original recommendation came from the federal Climate Change Authority, which advised the government to improve the accuracy of methane measurement, reporting and verification and to support methane mitigation across the coal and oil and gas subsectors. The panel says it will continue assessing different top-down approaches, source types and use cases, with the aim of identifying which can be used to update official methane estimates.

Coal's share of the emissions ledger

Under the methods currently used by the federal government to estimate pollution, coal mines account for about 5% of Australia's total greenhouse gas emissions — more than triple the fugitive emissions attributed to oil and gas facilities. The International Energy Agency is among the global bodies that have questioned the accuracy of methane reporting against what is actually venting into the atmosphere, with the energy sector potentially the most errant.

The non-profit Climate Council has raised the same question for Australian coal. Its 2024 report found that mines producing 7% of the country's coal were emitting about half of the national total of methane pollution, based on estimates that drew on aircraft and satellite sensors. The stakes are amplified by methane's potency: over a 20-year period it has a global warming potential more than 100 times greater than carbon dioxide.

What the technology can and cannot do

The report sets out clear limits on the measurement tools now available, and says top-down methods should complement rather than replace the bottom-up accounting miners currently use:

• Satellites are useful for finding large emitters and understanding emissions across regions, but cannot yet be used on their own to report emissions from individual sites.
• Airborne approaches show promise because they can detect smaller emissions across large areas.
• Ground-based and drone sensors form part of the same toolkit, with detections then used to quantify emissions.

David Etheridge, a former senior principal research scientist with the CSIRO, told Renew Economy that accurate measurement is difficult because concentration readings must be corrected for atmospheric dispersion. “If you're nearby a source when the atmosphere is not mixing very much, you [might] get a huge concentration but it may not actually be a very big source,” he said. His group applied emissions measurements to a coal seam gasfield in Queensland's Surat Basin a decade ago and found a bit more than was estimated from the bottom up.

Underground versus open-cut

Etheridge said emissions estimates from underground coal are reasonably well done, because mines typically hold a large reservoir of methane with few outlets. When gas is vented, operators can measure the concentration coming out and multiply it by the flow rate of the duct. Open-cut mines are harder, with methane escaping from many places at different times, and operators extrapolating from a few small experiments across a very large site — an approach he said can lead to errors that top-down methods would improve on.

The commercial dimension is not limited to compliance. Etheridge's research, including a 2020 paper led by Ben Hmiel, found that anthropogenic fossil emissions were underestimated by about 58 million tonnes of methane a year. He described that global underestimation as good news, because it identifies methane that can be mitigated and captured rather than lost: “It's a lost product. So we would like to actually collect that methane and burn it and use it.” With gas now more expensive, he said, companies have a stronger incentive to find and fix leaks. The report lands as Coal Australia, a lobby group representing the country's biggest coal miners, runs its “Forging the Future” campaign to keep coal communities strong.