It is commonly accepted that biogenic coalbed methane (CBM) is formed by anaerobic bacteria and methanogens via coal biodegradation. While the syntrophic cooperation between fungi and methanogens has been well-established in the production of methane from rumen, little is known about the role that fungi play in the formation of biogenic CBM. Miseq sequencing and mcrA gene library were employed to investigate the fungal, archaeal, and bacterial communities in produced water from Qinshui Basin, a major site for CBM exploitation in China. The syntrophic relationship between fungi degrading coal and methanogens producing methane was also investigated. A diversity of fungal communities was found in produced water from different coal seams with the dominance of Ascomycota and Basidiomycota. Hydrogenotrophic methanogens, Methanobacterium, were also found to be predominant in produced water as revealed by Miseq sequencing and mcrA gene library analysis. Bacterial communities with potential to degrade coal were also recovered in produced water. Large yields of methane were produced in incubations with produced water and coal. Incubations that included antibiotics achieved 62.24% to 97.53% of the methane production as compared to the incubations without antibiotics. These results confirmed that most of the biogenic gas was produced by hydrogenotrophic methanogens and demonstrated the important role that fungi play in the biodegradation of coal.

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Coalfield subsurface fires can result in ecological disasters of global dimensions. These fires are difficult to control therefore can result in colossal wastage of resources (the coal itself but the resources devoted to suppression), a serious negative impact on the environment and acute health problems for large populations. However, if the heat can be effectively recycled and utilized, the combustion energy will be recovered but also heat extraction can promote suppression. Thus, leading not only to a positive energy impact but to a reduction polluting emissions and consequent health issues. This paper presents the results of a feasibility analysis of the overall recovery of underground thermal resources of a novel system of Waste Heat Recovery Units (WHRUS) that combines thermosyphon and thermoelectric technologies. Both thermal equivalent model and numerical assessment are presented. A series of realistic-scale field experiment conducted in the Xinjiang's fire zone for an extended period are discussed. Using a local geothermic assessment, the heat recovered from subsurface coal fire can be estimated as the summation of the convective and conductive components of the energy generated. The average heat generated for the fire district is estimated at approximately 495 W/m 2 and the average extraction efficiency at approximately 58%. The WHRUS shows and excellent heat transfer performance with an effective lower resistance of approximately 0.0049 W/°C and maximum thermal recovery rate greater than 90%. Finally, while the thermoelectric

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The coal fires, a global catastrophe for hundreds of years, have been proved extremely difficult to control, and hit almost every coal-bearing area globally. Meanwhile, underground coal fires contain tremendous reservoir of geothermal energy. Approximately one billion tons of coal burns underground annually in the world, which could generate ~1000 GW per annum. A game-changing approach, environmentally sound thermal energy extraction from the intractable natural coalfield fires, is being developed by utilizing the waste energy and reducing the temperature of coalfield fires at the same time. Based on the Seebeck effect of thermoelectric materials, the temperature difference between the heat medium and cooling medium was employed to directly convert thermal energy into clean electrical energy. By the time of December 2016, the power generation from a single borehole at Daquan Lake fire district in Xinjiang has been exceeded 174.6 W. The field trial demonstrates that it is possible to exploit and utilize the waste heat resources in the treated coal fire areas. It promises a significant impact on the structure of global energy generation and can also promote progress in thermoelectric conversion materials, geothermal exploration, underground coal fires control and other energy related areas.

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