Aging behaviour of organic matter decomposition and microstructure of coal using hydrogen peroxide for bio-methane production in subsurface environment

Abstract

Microbial methanogenesis occurs in diverse subsurface environments. Biogenic methane is produced during the metabolism of methanogenic microorganisms. These microorganisms have the ability to produce methane using low-molecular-weight organic acids as substrates. These substrates are decomposed from hardly decomposable organic matter present in the source soil or rocks. An in situ clean-up method of ground contaminated with such compounds has been established, incorporating the Fenton reaction, utilising hydrogen peroxide and iron compounds. In this reaction, OH radicals are produced which can decompose toxic organic matter in the soil. With the aiming at developing of the production engineering of biogenic methane gas in the subsurface environments, we have proposed a new geotechnical method, known as Subsurface Cultivation and Gasification. This approach employs hydrogen peroxide to rapidly decompose organic matter. In this study, hydrogen peroxide solution immersion tests were performed on lignite in order to characterise the structural changes resulting from oxidation decomposition of hardly decomposable organic matter. It was found that the quantity of low-molecular-weight organic acids required for the microbial methanogenesis process increased with increasing immersion time. In addition, the interior structure of the lignite mass was significantly altered in the oxidation reaction, suggesting that the microorganism habitat space could be formed inside the source material itself.