Characterization of organic compounds from hydrogen peroxide-treated subbituminous coal and their composition changes during microbial methanogenesis

Abstract

Natural gas burns cleaner than coal by reducing ∼50% of the carbon footprint and emission of toxic substances and particulates. Coalbed natural gas can be produced from coal by indigenous microorganisms. Hydrogen peroxide treatment to coal has been shown to enhance the production of biogenic coalbed natural gas. In this study, we investigated methane generation from a subbituminous coal pretreated by hydrogen peroxide and the changes of the organic composition during gas production. We demonstrate that there is a great potential to produce natural gas from hydrogen peroxide-treated coal by microorganisms. The organic composition of the coal-derived compounds and the bulk organic profiling were changed because of the microbial degradation. The liquid samples before and after gas production were characterized by fluorescence spectrometer, GC/MS, HPLC, GPC, and TOCs. The results indicated that the chemical treatment has produced both labile organic components and compounds that are recalcitrant to microbial degradation. Labile compounds including short-chain carboxylic acids (C1 to C6) were found to contribute to the gas production. HPSEC analysis has shown shifts of molecular weight distributions, confirming organic composition changes. In addition, the analyses suggested that the labile organic compounds were conducive to shorten the lag phase of the gas production, whereas the presumed-recalcitrant constituents were surprisingly slightly biodegraded. The analysis also showed that the chemical treatment and biotransformation could produce compounds that are toxic to the environment. Environmental impacts should be fully evaluated before field applications.