Hydrogen production from cassava starch processing wastewater by two-stage thermophilic dark fermentation and microbial electrolysis was investigated. Single-chamber membrane-free microbial electrolysis cell with applied voltage of 0.6 V was optimum for hydrogen production with hydrogen yield of 245 ml H-2 gCOD(-1). Continuous microbial electrolysis reactor has a maximum hydrogen yield of 182 ml H2 gCOD(-1) at HRT of 48 h with energy recovery efficiency of 217%. The continuous integrated tw-stage dark fermentation and microbial electrolysis have hydrogen yield of 465 ml H-2 gCOD(-1) with 2 times hydrogen yield improving compared with a single stage and a maximum COD removal of 58% was achieved. Dominated bacteria at an anode of microbial electrolysis cell were exoelectrogens belong to Brevibacillus sp. Caloranaerobacter sp. and Geobacillus sp. Continuous two-stage thermophilic dark hydrogen fermentation and microbial electrolysis were efficient processes for hydrogen production from cassava starch processing wastewater. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.