Biogenic methane production from lignite in cube: Comparison of the inner and outer part of coal

The methane generation by coal biodegradation has been widely demonstrated in the laboratory. However, powder coal was mostly employed, and little is known about the methane production from coal in cube. A 2L fermenter was used here to perform the anaerobic degradation of lignite in cube by a fungi-methanogens mixed microflora. The results showed that the methane production reached 6578.51 mu mol. After degradation, the contents of carbon, oxygen, hydrogen, and aromatic functional groups decreased in the inner part of residual coal (Inc) and reduced more in the outer part (ExC), suggesting that microorganisms can act inside the coal matrix although the action weakens. The specific surface area (SSA) and pore volume (PV) decreased in Inc but Increased in ExC due to the antagonistic effect of biodegradation and the retention of organics and microorganisms. Fermentative fungi and Methanosarcina dominated in fermentation broth where acids, especially fatty acids were the main intermediates. The results revealed that methane generation by biodegradation also happened inside coal matrix, laying a fundamental basis for the application of microbially enhanced coalbed methane. And further efforts are needed to enhance biodegradation to improve methane production and pore development.