Biogenic methane production from coal has been demonstrated to be a universal process at places where coal and a suitable microbial community co-exist. Through stimulating activities of in situ microbial communities, higher methane production rate can be achieved compared to those without biostimulation. However, it is commonly observed that upon stimulation either in situ or ex situ, methane production will increase but halt after certain period of time. This study was thus designed to identify reasons for this behavior and provide insight on how to sustain coal biogasification over longer durations. It was found out that after methane production rate stopped increasing, coal, at the studied loading, was still bioavailable. The headspace gas and the coal degradation intermediates were not toxic or inhibitory to the bioconversion process. Instead, lack of nutrients, especially those provided through yeast extract and peptone was critical for sustained methane release from coal. Although these two nutrients could be used as carbon sources, negligible amount of methane was observed from control reactors without coal. At least, these were true for the microbial community and the bituminous coal investigated here. Thus, to convert coal to methane continuously at a high rate that is possible, site-specific nutrient solution needs to be supplemented periodically. Published by Elsevier Ltd.