Waste heat from anaerobic digesters can be converted to electricity by using thermoelectric generators (TEG). Herein, such energy was employed to power a microbial electrolysis cell (MEC) for producing hydrogen gas. Four TEG units could deliver a voltage of similar to 0.5 V, sufficient to drive the MEC that achieved a hydrogen production rate of 0.48 +/- 0.13 m(3) m(-3)d(-1). This rate was further improved to 0.75 +/- 0.05 m(3) m(-3) d(-1) when the temperature difference for TEG was increased from 18 to 28 degrees C. There was no significant difference between the TEG-powered MEC and power supply-supported MEC (at 0.6 V), in terms of current generation, hydrogen production, and organic removal. Ambient air was also studied as a cold-side source for TEG, although some challenges were encountered to maintain a large temperature difference. Those results will encourage further exploration of using TEG as a feasible power supply for sustainable MEC operation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.