Jharia coal fires may burn hotter, emit more greenhouse gases than thought

Fires that have been burning for decades beneath the Jharia coalfields in Jharkhand are releasing smoke and gas through cracks in the ground. And parts of this underground fire system may burn more and release more greenhouse gases than previously thought, according to a new study.

Researchers from the United Kingdom and India, including CSIR-Central Institute of Mining and Fuels Research (CIMFR), reported in a May 18 paper. Contact Earth and Environment It turns out that collapse structures formed as a result of underground fires consuming coal seams and destabilizing the rocks above them can extend more than 100 m vertically through the soil, releasing hot gases into the air.

When mining exposes coal to oxygen, natural oxidation reactions can trigger underground fires that smolder for decades. Previous estimates suggested that fires in the region were already emitting copious amounts of greenhouse gases, but because the fires spread unevenly, scientists had difficulty tracking them accurately.

The new study focused on the Ena, Bastacolla and Tisera mines. In 2018-2023, researchers used numerical modeling and mineralogical analysis to document collapsed structures up to 10 m wide, collecting samples of molten rock and glass-like materials and analyzing their composition.

Researchers found that larger cavities often had paralava: rocks melted and resolidified by the heat of coal fires. At Ena and Tisera, they found a type of molten, glass-covered rock they called “birianiite,” reflecting the rock’s mix of geological components and its similarity to the popular rice dish.

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Because it is difficult to directly measure the temperature inside actively collapsing structures, the researchers combined field observations with computer modelling. Their simulations suggested that large, isolated collapse structures could approach 4,000 C on paper in some conditions, a temperature much higher than estimates usually associated with underground coal fires.

Using modeling based on the amount of coal likely to be burned in structures, the team estimated the global warming potential of the fires in Jharia at up to 748.72 MT CO2.₂-equivalent per year – almost double the UK’s reported regional emissions in 2023.

While industrial emissions are subject to strict monitoring, fugitive emissions from uncontrolled coal fires like the one in Jharia rarely form part of global greenhouse gas controls. However, the authors acknowledged that their model excluded some real-world processes, including chemical reactions and mechanical deformation, that could alter the temperature forecast. Similarly, emissions estimation is highly dependent on assumptions about the extent of combustion, among other factors.

mukunth.v@thehindu.co.in