With one billion tons of methane produced annually by microorganisms, biogas production can be appreciated both for its role in global organic matter turnover and as energy source for humankind. Current operations tapping unconventional gas deposits generated by microbes in coal seams or harvesting methane from anaerobic waste digestion facilities are examples where a capacity to manipulate microbial community function for enhanced biogas formation would be desirable. Here we report a 10-18 fold increase in methane production through the application of a newly discovered structure of a semiconductive crystalline form of a synthetic phenazine that manipulates the fate of reducing equivalents as a means of accelerating methane production from coal and foodwaste. We discovered that the phenazine favours acetoclastic methanogenesis by delivering electrons directly to the terminal respiratory enzyme heterodisulfide reductase. In situ amendment of coal seam associated groundwater with the phenazine 80 m below ground level resulted in spontaneous crystal formation and a 5-10 fold increase in methane production, outperforming other enhancement methods shown in the past. Furthermore, this organic self-assembling semiconductor stimulated the biomass production of methanogenic archaea whilst the growth of sulfate-reducing bacteria was inhibited favouring methane production.