Development of a nutrient recipe for enhancing methane release from coal in the Illinois basin

Recent literature has shown that in order to enhance methane release from coal through biogasification, suitable nutrient solutions are needed to stimulate microbial activities toward coal depolymerization and conversion to biogas. Specific for bituminous coal in the Illinois basin, a nutrient recipe that can be used to enhance coal biogasification in situ is not available yet. To develop such a recipe, the formation water and the indigenous microbial community were first characterized in detail. Based on these characteristics and our previous experience working with Illinois coal, four parameters, Fe powder, methanol, ethanol, and trace minerals were optimized through using a Box-Behnken design. The optimal condition predicted by the models was: Fe-powder at 74 mM; methanol at 97.9 mM, ethanol at 100 mM, and trace minerals at 100%. Under these conditions, the predicted methane yield and content was 1417.35 ft3/ton and 80.7%, respectively. These results were then validated by experimental studies. In addition, each added component was evaluated in terms of its contribution to methane generated. Specifically, the role of coal in the biogasification process was studied against two other solid materials. Overall, this study demonstrated that coal can be converted to methane and nutrient solution can definitely enhance methane release from coal. The real effect of this recipe in improving methane release from coal in situ needs to be further evaluated in a field scale.