초록
Electrodialysis (ED) removed volatile fatty acids (VFAs) from a continually-fed, hydrogen-producing fermenter. Simultaneously, electrochemical removal and adsorption removed gaseous H<SUB>2</SUB> and CO<SUB>2</SUB>, respectively. Removing VFAs via ED in this novel process increased H<SUB>2</SUB> yields by a factor of 3.75 from 0.24molH<SUB>2</SUB>mol<SUP>-1</SUP><SUB>hexose</SUB> to 0.90molH<SUB>2</SUB>mol<SUP>-1</SUP><SUB>hexose</SUB>. VFA production and substrate utilisation rates were consistent with the hypothesis that end product inhibition arrests H<SUB>2</SUB> production. The methodology facilitated the recovery of 37g of VFAs, and 30L H<SUB>2</SUB> 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<SUB>2</SUB> production. To produce H<SUB>2</SUB> from real world, low grade biomass containing complex carbohydrates, longer hydraulic retention times (HRTs) are required. The proposed system increased H<SUB>2</SUB> yields via increased substrate utilisation over longer HRTs.