Enhancement of biomethane production by huminite-enriched lignite pretreated with hydrogen peroxide

Abstract

In situ bioconversion of low rank coal to natural gas is an attractive approach to reduce greenhouse gas emissions and utilize underexploited coal recourses. Hydrogen peroxide pretreatment followed by microbial conversion of coal to methane proved effective. However, what maceral component is more susceptible to solubilization and microbial conversion remains elusive. In this study, the dissolution of huminite-enriched Shengli lignite by hydrogen peroxide and its effects on the subsequent methane production by a microbial assemblage were investigated. The huminite was enriched and separated by a combination of hand-picking and floating-sink (isopycnic centrifugation) separation and treated with hydrogen peroxide. Both solid and liquid fractions of the treated coal were subjected to microbial conversion. Various analyses including Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography/Mass Spectrometry (GC/MS), High-Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC), and DNA sequencing were conducted for both solid and liquid fractions as well as samples after biomethanation. The study demonstrated unequivocally that the enrichment of huminite can improve solubilization and methane production, and that huminite is more accessible and biodegradable compared to other macerals. Microbial analysis revealed that the dominance of methanogens was associated with huminite. Overall, this study provides insight into the bioconversion of lignite to natural gas and suggests that huminite plays a crucial role in this process.