Comparison of coal rank for enhanced biogenic natural gas production

Biogenic natural gas production is often associated with low-rank coals such as lignite (brown coal) and subbituminous coal; however, little work has been done to determine the potential of stimulating microbial methane production in higher-rank coals. Reference samples of lignite, subbituminous, high-volatile bituminous, and low-volatile bituminous coal samples were obtained. A laboratory feasibility study was conducted in anaerobic microcosms containing each type of coal and amended with a nutrient solution and a methanogenic consortium of organisms enriched from formation water obtained from a coalbed methane well with a known history of biogenic gas production. Headspace analysis of the microcosms indicated that methane production rates were higher in the two bituminous coals than in the lower rank coals. The results suggest the potential for enhancing biogenic natural gas production from bituminous coals with a focus on liberating trapped volatile organic compounds.

► Biogenic natural gas most often associated with low-rank coals
► Laboratory microcosm yielded methane production in both low and high rank coals
► Results suggest methane production higher in bituminous than in low rank coals