State-level CMM emissions

Coal mine methane higher than reported in both major coal mining states

Queensland and New South Wales (NSW) are the two major coal producing states in Australia. Together they contribute more than 98% of Australia’s black coal production and all of its metallurgical coal. Queensland is the largest coal producing state in Australia, averaging close to 313 Mt of coal per year between 2015 and 2020, while NSW has produced slightly less, at approximately 252 Mt per year over the same period. 

Each state has a unique coal mine methane profile. Queensland recorded 626 kt of coal mine methane in 2020, with 58% of those emissions from underground coal mines and the remaining 42% from open-cut mines. This was the highest year on record for Queensland’s reported coal mine methane emissions, having grown 6% higher than 2019, and more than 350% greater than 1990. 

In contrast, 2020 was the third lowest year on record for officially reported coal mine methane emissions in NSW. The state recorded 379 kt of methane that year, followed by 339 kt in 2021. This was a significant shift, as emissions reported in 2020 were 40% lower than reported emissions in 1990, and 55% lower by 2021.

This was largely due to a significant emissions reduction from underground mines in NSW, which continue to make up more than 82% of all officially reported coal mine fugitive emissions. Fugitive emissions from underground mines had fallen by 53% in 2020 and 58% in 2021, compared to 1990 levels. This emissions reduction trend was largely due to the closure of older, gassier mines, and is further explored in an Ember report published earlier this year. 

Open-cut coal mines represent 76% of all black coal production in NSW, but make up a much smaller share of total coal mine methane fugitives. In 1990, open-cut mines recorded 67 kt of methane, representing less than 10% of the state’s total coal mine fugitives. By 2020, this relative share of coal mine fugitives had grown to 18%, but the total quantity of emissions recorded from open-cut mines had barely changed, recording 68 kt of methane that year. 

In this study, we sought to undertake a preliminary verification of these officially reported fugitive emissions, and to provide what we believe is the first representative satellite estimate of coal mine fugitives in each state. Through our six clusters, we assessed four key coal mining areas across Queensland’s Bowen basin. The average area of the four Queensland clusters was 16,661 km2 and collectively incorporated 79% of the state’s black coal production. Additionally, two clusters in NSW—incorporating the Hunter Valley and Illawarra coal fields—accounted for 60–64% of the state’s coal production in 2020 and 2021, with an average cluster area of 10,341 km2.

Operational oil and gas pipelines were found to cross through clusters in NSW and Queensland. Solid waste and landfill sites were also identified as potential methane sources in one cluster in NSW. A full explanation as to how uncertainty around methane sources was handled in this study is included in the Methodology section attached to this report.

Our TROPOMI-based satellite estimates reveal that methane emissions in Queensland could be significantly higher than reported. In 2020, Kayrros data indicate emissions of 0.69 ± 0.12 Mt methane—11% more than the total reported fugitive emissions from Queensland’s coal mines—despite modelling only four sub-regions of the state. This result is consistent with two other satellite studies that also suggest underreporting at the mine level.

Several satellite-based studies have been conducted in the Bowen Basin, Queensland, using TROPOMI observations. In 2021, Sadavarte used TROPOMI data to identify methane emission sources between 2018 and 2019. Another study by Palmer also used TROPOMI to identify major emission sources for 2019. In both studies, satellite-derived emission estimates were higher than Scope 1 emissions reported by the identified sources.

Sadavarte’s study identified three major methane plume sources across one surface mine and two underground mine clusters. This includes (1) Hail Creek (surface), (2) Broadmeadow, Moranbah North, and Grosvenor, and (3) Grasstree and Oaky North. Total emissions from these sources were estimated to have reached 0.57 ± 0.098 Mt CH4 per year, equivalent to approximately 15.96 Mt CO2e. This is 80% higher than the total reported scope-1 emissions for these sites and is largely attributed to Hail Creek.

Similarly, Palmer identified four major methane sources: (1) Hail Creek (surface), (2) Moranbah North and Broadmeadow, (3) Capcoal, and (4) Coppabella (surface). The total emissions from these sources were estimated at 8.5 Mt CO₂e. This is equivalent to a 27% increase compared to reported scope-1 emissions, which includes not only fugitive emissions, but also the emissions from diesel combustion and land clearing.

Both studies highlight a significant discrepancy between reported and estimated emissions, particularly for surface mines. Emissions estimates using satellite analysis on Hail Creek are 2.4 (Palmer) to 12.9 (Sadavarte) times higher than reported values.

Borchardt conducted airborne measurements in September 2023 over Hail Creek mine.  During the flyover, the aircraft measured methane concentrations in two ways: direct sampling at the aircraft’s location during flight and LIDAR mapping, which captured methane distribution at a high spatial resolution. Using these observations, they estimated methane emissions from the mine.

The results indicate that emissions were 4–5 times higher than reported, assuming they were representative of average operational conditions over the reporting period. Both methods produced comparable estimates, with direct measurements at 2.36 ± 0.46 MtCO₂e per year and a slightly higher estimate from LIDAR mapping at 2.77 ± 1.30 MtCO₂e per year.

These estimates fall within the range of satellite observations from 2018–2019, exceeding Palmer’s estimate (1.20 ± 0.60 MtCO₂e) but remaining lower than Sadavarte’s (6.44 ± 1.40 MtCO₂e).

Our findings in New South Wales (NSW) indicate a significant departure from officially reported emissions. While the state reported 379 kt of methane in 2020, our satellite study identified 721 kt of methane that year, while only accounting for approximately 61% of the state’s coal production. While this estimate has an uncertainty range of 566 – 876 kt, this still represents a significantly higher figure than official reporting.

In 2021, our satellite estimate had a similar finding. While officially reported coal mine methane emissions dropped to 329 kt of methane, our satellite estimate identified 679 kt of methane with an uncertainty range of 533 – 825 kt of methane. This represents 106% higher emissions, while only capturing 64% of all coal production in the state that year.