Enhanced biological hydrogen production through the separation of volatile fatty acids and ammonia based on microbial bipolar electrodialysis during thermal dark fermentation

Biological hydrogen (H2) is a clean fuel which can be produced by dark fermentation of food waste (FW). Some inhibitors including volatile fatty acids (VFAs) and ammonia can influence on H2 production rate. In the present work, a bio-electrochemical system, Thermal Dark Fermentation - Microbial Bipolar Electrodialysis (TDF-MBED) process, was used to separate VFAs and ammonia during FW fermentation, and thereby enhancing H2 production. From the three configurations employed, that novel design which consisted of two Anion Exchange Membranes (AEM), one on the anode side and another on the cathode side of working chamber (WC) had better results. The cumulative H2 increased from 2879 to 3511 mL L−1 as well as H2 production yield increased from 51 to 63.15 mL mg−1 compared to control, while at the same time, 50 mL H2 was produced in the cathode chamber. The VFAs concentration raised up to 507 mg L−1 in the separation chamber after 24 h. Although the VFAs production in TDF-MBED increased up to 2314 mg L−1 compared to 714 mg L−1 in the control, pH value remained above 5.15 (0.65 higher) during 24 h. In the configuration that contains two AEM, alkalinity and ammonia remained higher than other configurations, which are favorable for H2 production. Moreover, when cation exchange membrane (CEM) was used, the ammonia separation became higher and its concentration in fermenter decreased sharply from 1372 to 952 mg L−1 during 10–24 h. The TDF-MBED is a promising bio-electrochemical and sustainable approach for enhancing simultaneous H2 and VFAs production during TDF of FW.