Electrohydrogenesis or biocatalyzed electrolysis is the name given to a process for generating hydrogen gas from organic matter being decomposed by bacteria.  This process uses a modified fuel cell to contain the organic matter and water.  A small amount, 0.2–0.8 V of electricity is used, the original article reports an overall energy efficiency of 288% can be achieved (this is computed relative to the amount of electricity used, waste heat lowers the overall efficiency).  This work was reported by Cheng and Logan.