Bioconversion of coal to methane has many economic and environmental advantages over more conventional processes. This study summarizes data on the stimulation of generation of methane from a subbituminous coal treated with potassium permanganate (KMnO4) as a depolymerization agent. The general bioavailability of the soluble coal-derived components is also evaluated by the aerobic production of CO2. Of the total coal carbon, 5.4% was solubilized into the aqueous phase. Based on aerobic and anaerobic bioassay, 27.7% of the soluble carbon was used as substrate by microorganism to produce carbon dioxide (CO2), and 3.2% was used to produce methane (CH4). The methane accumulated rapidly and peaked at day 40 with 93.4 mu mol CH4/g coal. A small fraction of the soluble carbon (143.0 mu mol CH4/g coal) was designated as volatile and was removed by sparging with nitrogen gas. This fraction was shown to have a significant impact on gas generation. The findings of this study provide the basis for a better understanding of the underlying processes involved in the rate-limiting step of coal solubilization; moreover, they provide evidence of the significant potential for the in situ/ex situ enhancement of biogenic natural gas production in depleted hydrocarbon reserves such as coal. The aerobic and anaerobic bioassays may be useful to evaluate sites for field applications intended to enhance methane production processes. (C) 2013 Elsevier Ltd. All rights reserved.