There are growing concerns that fugitive methane emitted by Australian coal mines – an often-invisible consequence of drilling into coal seams – is being vastly underreported and could prevent Australia reaching its emissions reduction targets.
Australia was responsible for 1.5 per cent of the 120 million tonnes of methane released into the atmosphere globally in 2023, according to data published by the International
Energy Agency’s (IEA) Global Methane Tracker in a March 2024 update.
Australia is the world’s fourth largest coal mine methane emitter, yet multiple independent analyses have shown much of the country’s fugitive methane emissions go unreported.
The IEA suggested that Australia was underreporting its fossil fuel sector methane emissions by about 60 per cent, with its estimate of 1.668 million tonnes of methane emitted in 2023 significantly higher than the 1.007 million tonnes Australia reported to the United Nations.
The IEA said: “Methane abatement in the fossil fuel industry is one of the most pragmatic and lowest cost options to reduce greenhouse gas emissions.
“Forty-six per cent of coal mine methane (about 765,000 tonnes) could be avoided by mine degasification and ventilation air methane abatement and additional measures, with 9 per cent of this reduction achievable at no net cost.”
Moreover, coal mines were shown to be a larger contributor to Australia’s methane emissions than both oil and gas production in a 2022 report by independent energy thinktank Ember.
Open pit mines in particular have the greatest disparity between reported and measured emissions, such as the Hail Creek mine in Queensland, which was shown to be leaking more than 10 times the amount reported to regulators.
Queensland and NSW, where most of Australia’s coal mining takes place, have the most methane emissions in the country.
In 2022, officially reported fugitive methane accounted for 8.9 per cent of NSW’s total greenhouse gas emissions, most of which was ventilation air methane (VAM) from underground mines.
Recent analysis of historical satellite data dating back to July 2022 by the Open Methane project also found that Australia’s official methane emissions data was significantly underestimating methane levels near identified hotspots.
Formed and majority-funded by renewable energy-focused not-for-profit The Superpower Institute, the Open Methane project integrates satellite data with atmospheric modelling to provide a scientifically robust framework for assessing methane emissions more accurately.
Rather than validating official reporting, Open Methane’s results more closely aligned with an alternative dataset provided by Climate TRACE, which showed methane emissions were 2.5 times higher than the official statistics.
Atmospheric physicist Emeritus Professor Peter Rayner, Open Methane’s lead researcher and Science Lead at the Superpower Institute, noted the finding not only cast doubt on the accuracy of Australia’s self-reported methane estimates but also underscored the potential for significant underreporting of emissions.
Prof Rayner said: “The discrepancy between the official data from the National Inventory and the atmospheric measurements as observed by the Sentinel 5P satellite indicates a large uncertainty in current reporting methods.
“This suggests that policies based on these figures may be inefficient or ineffective in addressing methane’s impact on climate.”
He added that the initial results unequivocally showed the federal government needed to mandate measurement by industry operators, measuring actual emissions from specific locations instead of using averages based on decades-old industry data for mining each tonne of coal.
While underground mining is generally the most emissions-intensive, the vast majority (75 per cent) of Australian coal mining is conducted by purely open-cut or surface methods, compared to only 16 per cent purely underground.
Underground mines typically have an outsized share in fugitive methane emissions, but the prevalence of surface coal mines and their lack of emissions monitoring and reporting highlights the urgent need for policy action on open-cut mines to achieve meaningful change.
In July, the federal government amended the National Greenhouse and Energy Reporting (NGER) Scheme legislation, part of which is the staggered phase-out of the current lowest-order methane emissions reporting method (method one) for opencut coal extraction at facilities covered by the Safeguard Mechanism.
Method one involves the use of default emission factors to estimate emissions based on those used in Australia’s national inventory.
Once phased out, relevant facilities will be required to use method two (a facility-specific method using industry sampling and Australian or international standards for estimation), or method three (a higher-level facility-specific method).
However, fugitive methane emitters who are not covered by the Safeguard Mechanism will still be able to use method one to estimate their methane emissions.
In a government submission, the Institute for Energy Economics and Financial Analysis (IEEFA) recommended that method three should be the lowest-order estimation method permitted for open-cut coal mines, as method two was also ineffective in making accurate estimations of methane emissions.
Method four, the highest order within the hierarchy, provides for direct monitoring of emissions, either on a continuous or periodic basis.
Andrew Gorringe, Energy Finance Analyst for Australian Coal at IEEFA, noted that methane abatement was necessary in underground mines for safety reasons, but was rarely performed at surface mines.
He said: “Nonetheless, in coal fields with high methane content and good gas permeability, there is an opportunity in open cut mining to pre-drain the gas from the coal seam prior to the drill and blast activity releasing the gas.
“More needs to be done to incentivise methane abatement projects not only at underground mines, but also for open cut, to ensure that the runaway growth of the large open pit mines in Australia do not put emissions reduction targets beyond reach.”
New technologies will be pivotal to abatement projects, with interest growing in the use of catalysts to improve thermal oxidation processes.
Thermal oxidation is an effective way of abating VAM, using reactor technology to oxidise more than 99 per cent of methane in a combustion chamber which is hot enough to convert methane into water and carbon dioxide.
Notably, the technology has the ability to be self-sustaining and does not need additional energy to maintain the combustion chamber’s temperature.
However, this can be technically challenging for operators, due to the high temperatures involved, the large air volume, and the methane resource being dilute and variable in concentration.
Research organisation Mining3 together with Low Emission Technology Australia (LETA), which focuses on reducing coal sector carbon emissions, recently began a collaborative project to investigate catalytic oxidation technology in the pursuit of lower VAM emissions.
The technology has the potential to operate at lower concentrations and temperatures compared to conventional methods, and the project will assess its suitability for safe and large-scale deployment in Australia.
Incorporating a catalyst into the thermal oxidisation process can significantly lower the temperature of VAM oxidation, with past research showing a reduction in VAM mitigator operating temperature to between 350 and 600 degrees Celsius.
Typical VAM thermal oxidation process temperatures are greater than 1,000 degrees Celsius, requiring specialised and high-cost ceramic materials to prevent stone dust composition from occurring at about 950 degrees Celsius, which generates calcium oxide causing sintering and ceramic corrosion.
Along with the lower operating temperature benefitting safety management, catalytic oxidation can process more ventilation airflow than a thermal oxidation unit, resulting in smaller mitigation equipment and a smaller footprint.
