Sustaining biogenic methane release from Illinois coal in a fermentor for one year

To evaluate coal biogasification in a larger reactor over a longer duration as compared to studies reported so far, a 3-liter fermentor was established. During the one-year study, a nutrient recipe was added three times to sustain methane release from Illinois bituminous coal. The cumulated methane production was 5171 ft³/ton with a methane content of 75.4% on day 365. After the fermentation was terminated, the residual coal and fermentation broth were characterized in detail. Compared to the untreated coal, the treated coal residue appeared to be finer and highly degraded with less carbon but more ash. Based on mass balance, volatile and fixed carbon decreased 15.9% and 29.6%, respectively, using the untreated coal as the baseline. According to GC/MS analysis, the fermentation broth contained mainly three groups of compounds: fatty acids and their derivatives, aromatics, and hydrocarbons. In addition, the fermentation broth was found to have effect on flocculation and contained compounds that possessed surface-active properties. Further investigations are needed to identify these chemicals responsible for these activities and develop ways to further enhance coal biogasification based upon results obtained then.