Estimating CMM emissions

Satellite estimates indicate significant methane underestimate

Australia’s coal mine fugitive emissions have come under intense international scrutiny over the past couple of years. A diverse array of international and peer-reviewed satellite estimates have identified considerably higher emissions from a range of underground and open-cut coal mines.

Following widely publicised research, the Australian government responded to these concerns through a year-long review of the national emissions reporting system. In its conclusion, the Climate Change Authority recommended a series of changes required to improve transparency, review measurement approaches, and integrate top-down emissions verification at coal mines across Australia.

Since then, preliminary findings from Open Methane utilising a combination of atmospheric modelling and satellite measurements have estimated that Australia’s coal mines and gas fields may be emitting twice as much methane as currently reported. More recently, a numerical modelling re-evaluation of current approaches for estimating fugitive emissions at open-cut coal mines found that existing company-led approaches may be underestimating fugitive scope-1 emissions by a factor of 3.6 to 4.2.

In this report, we contribute to the growing body of evidence through a satellite assessment of fugitive methane emissions from coal mines across New South Wales (NSW) and Queensland. The collaborative study with energy intelligence firm Kayrros, utilised TROPOMI satellite observations across six coal mining clusters while controlling for wind effects and non-fossil methane sources. The locations of the coal mining clusters are shown below.

The study area covers 79% of Australia’s total black coal production in 2020, and more than 90% of its metallurgical coal production that year. Of the six clusters, four were located in Queensland, incorporating 79% of the state’s total black coal production and 97% of its metallurgical coal production. Queensland is the world’s largest seaborne exporter of metallurgical coal, with significant exports into Asian and European markets.

An additional two clusters were located in New South Wales across the Hunter Valley and Illawarra coal fields, covering 60 to 64% of the state’s coal output and more than 70% of its metallurgical coal sales. As such, we expect that our results for both national and state-based emissions comparisons should be considered to be highly conservative. An in-depth description of the methods used to develop these estimates is in the supporting material. 

According to preliminary findings from our study, satellite estimates across these six clusters identified a total of 1.42 ± 0.19 million tonnes of methane released from coal mines in 2020. This is significantly higher than the 1.01 million tonnes of methane that was officially reported by the National Greenhouse Accounts that year. 

This estimate aligns with satellite results from  Shen estimated that Australian coal mine methane emissions from May 2018 to February 2020 could be closer to 1.6 million tonnes annually. This was nearly 60% higher than the officially reported estimate of 0.974 million tonnes of methane in 2019. Despite slight differences in the study’s time periods, this remains a significant discrepancy. 

The study also seeks to compare these cluster-based satellite estimates to state-based emissions estimates, perhaps for the first time. The results for our limited area assessments, indicate that satellite estimates for both Queensland and NSW in 2020 are significantly higher than total reported coal mine fugitive emissions in both states. In NSW, an additional comparison for 2021 identified fugitive emissions levels more than twice as high as officially reported, while only incorporating half the state’s coal production.