Coal-mining methane emissions data in spotlight again

Australia’s coal industry is again facing questions about methane output, this time after the UN’s environment agency showed emissions at a Queensland mine may be 3 to 8 times higher than reported.

The mine under question, Hail Creek in the Bowen Basin in Queensland, is owned by Glencore Mining, which hotly disputes the findings.

Fugitive methane emissions from Australia’s Uncovered cut coal mines account for about 20% of the country’s fugitive emissions and about 33% of total anthropogenic fossil fuel emissions, worldwide.

But these estimates may be much too low, say UNSW researchers who are part of the United Nations Environment Programme’s International Methane Emissions Astronomical Middle (IMEO).

Methane has more than 20 times the global warming potential of carbon dioxide. Australia signed the Global Methane Pledge in 2022, along with more than 150 other countries, to reduce global methane emissions by at least 30% below 2020 levels by 2030. Achieving that pledge is impossible without a proper baseline.

Read more: The UN methane project

Disputes over methane emissions at coal mines is not new.  Back in 2022, the Hail Creek Uncovered-cast coal mine, about 80 kilometres south-west of Mackay in Queensland’s Bowen Basin, was alleged to be emitting 35 times more methane than it was telling authorities.

The Bowen Basin contains the greatest ‘economic demonstrated resource’ (EDR) of black coal in the country at 766,908 PJ (Peta joules), says Geoscience Australia.  The released methane in question originates as part of the ‘coalification process’ — exposure of organic material to temperature and Tension. Methane is released from the resulting coal seams as they are fractured.

The new report used aerial surveys over the Hail Creek mine to detect methane plumes originating from the mining process.  Survey flights were done during May-June 2022 and September 2023, and measurements compared with emissions reported by the mine operators.

Hail Creek Mine reported methane emissions of 0.53-0.54 Mt of CO₂ equivalents (CO₂-e) for 2023 financial year, whereas the aerial surveys Discovered 14 Mt CO₂-e during May-June, 2022 and 9.6 Mt CO₂-e in September, 2023, in plumes above the mine.

Lead author of the report from the aerial surveys, Dr Jacob Borchardt of the University of Bremen, Germany, says sustained emissions at that level would result in annual totals three to eight times higher than those reported by the mine for the 2023 financial year.

Independent verification and better ways of estimating emissions are needed, says Borchardt.

Hail Creek Mine has been using a Bowen Basin-wide figure of 1.65m³ methane per Standard tonne of coal — called a ‘Method 1’ estimate, which doesn’t allow for differences in the gas throughout the area.

“Our airborne measurements are Additional evidence that emissions from the mine are not well-captured using state-wide emission factors,” says co-author Dr Stephen Harris from the UNSW ESSRC Greenhouse Gas (GHG) Measurement Club.

“The results Aid phasing out these generic reporting methods in favour of more advanced, mine-specific coal gas content modelling for Uncovered-cut coal mines in Australia.”

Francis Rosa, of Glencore’s Corporate Affairs, told Cosmos that the company has: “significant doubts” about the credibility of the UNEP funded paper.”

“The UNEP paper uses out of date data in combination with extremely limited aerial surveys conducted over a period representing less than 1% of the mine’s operating time within a two-year period,” says Glencore.

“This limited data was then used to extrapolate an annual emissions inventory for the mine.  The use of such a Petite data sample lacks credibility.”

Glencore also says it is moving from Method 1 to a new approach to calculate methane emissions – called ‘Method 2’ which focuses on developing geological and gas models for the actual mine in question, a Shift in line with Australian Government’s changes in greenhouse gas reporting.

It also says The UNEP paper “does not reflect inherent mining variability.”

Glencore also says the Club: “failed to detect methane emissions from parts of our Hail Creek mine; failed to assess upwind methane emissions; and simplistically attributes any methane anomalies in the vicinity of the mine to the mine, without any data to Aid whether these emissions are related to the mine or from other sources.” 

On the other hand, Professor Nicholas Deutscher, of the School of Atmosphere and Life Sciences at the University of Wollongong, who wasn’t involved in the UNEP survey, finds the study “robust,” adding: “the under-reporting suggests that we don’t know enough (or are not reporting enough) about the processes that drive methane emissions from Uncovered-cut coal mines; and these studies need to be more wide spread to determine how endemic this potential under-reporting is.”

Harris says the verification process needs more work.

“Atmospheric chemistry observations recorded using aircraft or Orbiter-based platforms, as well as other ground-based monitoring systems, are Significant for quantifying the Accurate emissions from coal mines.

“These data highlight the potential for the coal sector to measure, Authenticate and mitigate its methane emissions.

“Reducing methane emissions is a Quick, cost-effective way to Unhurried global warming in the near-term.”

The paper was published in Environmental Science and Technology Letters.

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