To optimize methane production from bituminous coal through use of a well-studied microbial community derived from the same Illinois basin in USA, a total of 12 parameters were first evaluated by setting up 64 reactors following a 2-level factorial design. Among the 12 parameters, temperature, coal loading, particle size and ethanol were found to have statistically significant effects on methane content and yield from coal. Following screening, to identify optimal value for each significant factor, a Box-Behnken design necessitating 29 reactors was adopted. Optimal conditions provided by the Design of Expert software for the highest methane yield were: temperature, 32 degrees C; coal loading, 201.98 g/L; coal particle size, <73.99 mu m; and ethanol at 300 mM. Under these optimum conditions, the predicted methane yield and content was 2957.4 ft(3)/ton (83.7 mm(3)/ton) and 74.2%, respectively. To confirm the predicted results, a verification experiment was conducted, where a methane yield of 2900 ft3/ton (82.1 mm(3)/ton) with a methane content of 70% was observed. Thus, models developed from this study can be used to predict methane content and yield from bituminous coal through biogasification ex situ. Published by Elsevier Ltd.