Fundamental Study on Compressive Characteristics of Artificial Coal Seam and Chemical Characteristics of Pore Fluid while Accelerating Decomposition of Organic Matter Using Hydrogen Peroxide

We proposed a new gasification method to convert unused organic matter in sedimentary rocks to bio methane gas using microorganisms, known as Subsurface Cultivation and Gasification (SCG). Our approach uses hydrogen peroxide (H2O2) to decompose organic matter rapidly into usable substrates for methanogens. We previously reported that H2O2 would be useful for effective SCG at lignite, and conversion of organic matter from lignite into biogenic methane with the help of microorganisms is expected to be highly profitable. However, physical properties of the sedimentary rock are thought to change with the decomposition of sedimentary rock in the SCG method. A series of one-dimensional compression tests were performed for artificial coal seams prepared using the lignite sampled from Tempoku coalfield in the northern Hokkaido to investigate the stability of coal seam during an industrial production of substrates for methanogens in the subsurface environment. H2O2 was used in the one-dimensional compression tests to produce lower-molecular-weight organic components as a substrate of methanogen. Moreover, H2O2 solution was repeatedly injected into the artificial coal seam under compressive pressure. Oxidative decomposition of the artificial coal seam produced a high yield of low-molecular-weight organic acids. However, settlement of the artificial coal seam subjected constant loading was dependent on concentration and injection amount of H2O2. The biomethane deposits might become mechanically unstable during promoting decomposition of organic matter of coal seams, even if lignite has the greater resource potential for biomethane.