Field conditions for the synergistic increase of biomethane in the goaf of coal mines filled with corn straw

Synergistic fermentation of coal and corn straw is an effective tool to increase biomethane production. However, a large gap exists between the biomethane production conditions of corn straw filling coal mine goafs and laboratory experiments. In order to determine the effect of the field environment on synergistic biomethane production, biomethane production experiments with coal and corn straw were carried out under different conditions to find the key factors restricting the potential of biomethane production. The obtained results showed that various bacterial sources had significant influences on the biomethane production of coal and corn straw, and domesticated bacterial sources provided fermentation systems with more efficient biomethane production capacities than mine water sources. Biomethane production of coal and corn straw was relatively high under mixed conditions, but it was also promoted under unmixed conditions. Different inorganic minerals had different effects on synergistic biomethane production, which varied. For example, calcite, montmorillonite, and kaolin are common minerals in coal-bearing strata that significantly enhance synergistic biomethane production of coal and corn straw. However, pyrite was found to significantly inhibit the synergistic biomethane production effect of coal and corn straw. Highly metamorphosed anthracite coal also presented biomethane production potential when stimulated by corn straw as a carbon source. The obtained results revealed the influences of different field conditions on the biomethane production of coal and corn straw and provided a reference for the field application of corn straw filling in coal mine goafs.