Electrodialysis (ED) removed volatile fatty acids (VFAs) from a continually-fed, hydrogen-producing fermenter. Simultaneously, electrochemical removal and adsorption removed gaseous H-2 and CO2, respectively. Removing VFAs via ED in this novel process increased H2 yields by a factor of 3.75 from 0.24 mol H2mol(hexose)(1) to 0.90 mol H-2 moL(hexose)(1). VFA production and substrate utilisation rates were consistent with the hypothesis that end product inhibition arrests H-2 production. The methodology facilitated the recovery of 37 g of VFAs, and 30 L H-2 that was more than 99% pure, both of which are valuable, energy dense chemicals. Typically, short hydraulic and solid retention times, and depressed pH levels are used to suppress methanogenesis, but this limits H-2 production. To produce H2 from real world, low grade biomass containing complex carbohydrates, longer hydraulic retention times (HRTs) are required. The proposed system increased H-2 yields via increased substrate utilisation over longer HRTs. Crown Copyright (C) 2017 Published by Elsevier Ltd. All rights reserved.