Characterizing microbial communities dedicated for conversion of coal to methane in situ and ex situ

Abstract

To enhance methane production in situ in bituminous coal seams, distribution of microorganisms in the formation water collected from a coalbed methane well was investigated. Based on next generation DNA sequencing, both bacteria (231 species) and archaea (33 species) were identified. Among the bacterial kingdom, polymer-degrading, benzoate, fatty acid and sugar utilizing bacteria were dominant. Among the archaea domain, the major methanogens (89.8%) belonged to the order of Methanobacteriales which are hydrogenotrophic. To develop a microbial consortium for ex situ coal bioconversion, the original microbial community was adapted to ground coals for five months in a laboratory environment. DNA sequencing revealed the presence of 185 bacteria species and nine archaea species which were dramatically different from those in the original formation water. In particular, the majority (90.4%) of methanogens were under the order of Methanomicrobiales. To increase methane production, two nutrient solutions were tested. Solution #2 which targeted methanogens provided a methane yield of 111ft3/ton in 20days, which translated to a 5.6ft3/ton-day. In addition, the adapted consortium was found to be aerotolerant.