Hail Creek Mine

Coal Production

During the sale of its interest in the mine, Rio Tinto reported that in 2017 the Hail Creek operation produced approximately 9.4 ($\mathrm{Mt}$) of saleable coal, comprising 5.25 ($\mathrm{Mt}$) of hard coking coal and 4.13 ($\mathrm{Mt}$) of thermal coal Rio Tinto, 2018 . In August 2018, Glencore became the operator of the Hail Creek mine after acquiring a majority interest in the operation and the surrounding coal resources.

The activity data used in Sadavarte, et al., 2021 , reproduced in Table 1 above, are not explicitly referenced in the original publication. Reported production values are 7.7 ($\mathrm{Mt}$) for 2018-2019 and 5.8 ($\mathrm{Mt}$) for 2019-2020. The paper refers to a gridded dataset described in Sadavarte, et al., 2022 , in which the grid cell centred at latitude -21.5° and longitude 148.35° reports a coal production value of 5.5865655 ($\mathrm{Mt}$). This value appears to be derived from a Queensland Government dataset that is no longer publicly accessible. The gridded dataset itself is available for download via Zenodo .

The Queensland Government publishes two primary statistical datasets related to coal production. The first, Coal Industry Statistical Tables FY 2010 - current , is released annually and provides a continuous time series from 2010 to the most recent reporting year. Within this dataset, the worksheet titled Coal production by mine reports, for each mine, year, and coal type, three key production metrics: Gross Raw Feed, Gross Raw Output, and Net Output , defined as follows:

Gross-Raw Output:

This is the amount, in tonnes, of raw coal produced as a result of mining activities undertaken at the mine during the period. Irrespective of whether or not some/all of that coal may be subsequently sold without being beneficiated, in providing this figure, the assumption is to be made that all coal mined at the coal face(s) during the period is delivered to the Run-of-Mine stockpile.

Gross-Raw Feed:

This is the amount, in tonnes, of raw coal received by the processing plant and any tonnage bypassing the plant to become saleable product during the reporting period.

Net Output:

The total amount, in tonnes, of saleable coal produced during the period, i.e. washed saleable product PLUS other saleable product. For tailings recovery operations, the total saleable output for the period is required.

An extract of the Hail Creek coal production data from these statistics is provided in Table 4.

This information is summarised in Figure 6 below, which indicates a qualitative change in production characteristics following the transfer of ownership from BHP to Glencore. While this shift may partly reflect changes in data definitions or reporting practices, it is also possible that the wash plant began processing coal from additional sources beyond the Hail Creek mine.

For FY 2019 (July 2018-June 2019), Palmer, et al., 2021 cite the Coal Industry Statistical Tables FY 2010 - current , which report a Gross Raw Output of 7.66 ($\mathrm{Mt}$) for Hail Creek. It is likely that this same value was adopted by Sadavarte, et al., 2021 .

For FY 2020, we were unable to identify the source of the 5.8 ($\mathrm{Mt}$) production value used by Sadavarte, et al., 2021 .

The second annually updated dataset is Annual Coal Statistics CY 2017 - current . This workbook includes a spreadsheet titled Top 10 producing mines, which reports two metrics, Total Net Output and otal Gross Raw OutputT, using the same definitions as those in the Coal Industry Statistical Tables. According to this dataset, the Hail Creek mine ranked 10^th in Total Net Output in both 2018 and 2019, while it did not appear in the top-10 ranking for Total Gross Raw Output during those years. In contrast, in 2020 and 2021, Hail Creek entered the top-10 list for Total Gross Raw Output, ranking 8 ^th, while simultaneously dropping out of the top-10 ranking for Total Net Output.

An extract of the Hail Creek coal production data from these statistics is provided in Table 5.

It is worth noting that in calendar year (CY) 2019, the Gross Raw Output of the 10 ^th ranked mine was 10,443,890 ($t$); in CY 2018 it was 11,057,616 ($t$); and in CY 2017 it was 10,022,541 ($t$). Because Hail Creek did not appear in the top-10 Gross Raw Output ranking during these years, these values represent upper bounds on Hail Creek's Gross Raw Output for the corresponding periods.

These datasets are difficult to reconcile and interpret consistently. As the primary objective of this work is the development and demonstration of software tools, we leave the resolution and interpretation of these data discrepancies to the reader and the respective data providers.

Methane Emissions

At the time of writing, several emission estimates are available for different time periods. These estimates are summarised in Table 6 below.

Please note that the Open Methane dataset is currently in a beta stage and is undergoing recalculation for 2023. The official release of the validated dataset is expected by the end of 2025 (private communication, Lindsey Gaines, The Superpower Institute, 23 July 2025).

Methane emissions reported by Glencore under the National Greenhouse and Energy Reporting (NGER) scheme are not publicly available; however, it is likely that they are calculated using one of the emission factors recommended under the NGER framework, applied to reported activity data.

Implied Emission Factor

The Implied Emission Factor (IEF) is calculated as the ratio of estimated ${\mathrm{CH}}_4$ emissions to reported raw coal production activity data. In the analysis presented in the Sadavarte, et al., 2021 Supporting Information , ${\mathrm{CH}}_4$ emissions for the years 2018 and 2019 are estimated at approximately 230 ($\frac{\mathrm{Gg}}{\mathrm{year}}$) each, yielding a combined total of 460 ($\mathrm{Gg}$). The corresponding activity data are taken as the sum of raw coal production for the same period ( $7.7+5.8$($\mathrm{Mt}$) ), resulting in an implied emission factor of