154 2. ROCK MASS DEGASSING IS KEY TO REDUCING METHANE EMISSIONS FROM COAL MINES The basic and most effective way to combat the methane hazard in hard coal mines is rock mass degassing. The efficiency of methane drainage at JSW mines in 2024 was almost 38%, with the efficiency of degassing in longwall mining areas with methane drainage reaching almost 60%. This means that as much as 60% of the methane released during coal mining is captured by the methane drainage system, but only 38% of the total methane released into the mine workings. This is due to the fact that the structure of methane release includes not only methane from areas under exploitation, but also from drilled corridor excavations and post-mining goafs. From closed post-mining areas, methane migrates through cracks in the rock mass to active workings that serve as ventilation routes on inactive levels of the mine. This does not pose a direct threat to the working crew because the methane concentration is low. However, the amount of methane released in this way over a long period of time is significant and can amount to several hundred thousand cubic meters per year. Table 5 - Methane drainage efficiency at JSW in 2018-2024 Year Mine methane drainage efficiency Methane drainage efficiency from walls with methane drainage system 2018 32,3% 51,9% 2019 34,9% 47,6% 2020 39,5% 52,8% 2021 42,8% 55,3% 2022 34,0% 40,1% 2023 34,3% 47,3% 2024 38,0% 58,7% Typically, the methane concentration in gas captured by the methane drainage system ranges from 40% to 60%, and according to Polish mining regulations, it cannot be lower than 30%. Often, the gas emitted from post-mining goafs has a lower methane concentration and capturing it would be unprofitable and non-compliant with regulations. This causes gas release into ventilation system, from where it is discharged into the atmosphere through ventilation shafts. To address this problem the project was launched on 1 March 2023, entitled ‘Reduction of methane emissions from post-mining areas in order to minimize the flow of methane into the ventilation air’. The project, known by the acronym REM, aims to reduce methane emissions from active mines into the ventilation air, which is then discharged into the
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