Degradation of dark fermentation effluents for biogas production using bioelectrochemical systems

Dark fermentation for H2 production was a promising bioenergy, as it could use straw and/or wastewater containing high organics as raw materials. The accumulated volatile fatty acids (VFAs), which were produced during the process of hydrogen fermentation, significantly inhibit the process of hydrogen production in the dark fermentation. Herein, bioelectrochemical system (BES) was used to treat the effluent of dark fermentation. A microbial electrolysis cell (MEC) was firstly used to treat the effluents of dark fermentation. Accompanied with hydrogen production in MEC, the pH value of the effluents increased from 4.5 to 8.7. Then the near-neutral effluents were used for methane production using a single-chamber microbial electrosynthesis system (MES), in which methanogens acted as biocatalysts to reduce CO2 to CH4. The results showed that the chemical oxygen demand (COD) removal efficiency and CH4 production rate of single-chamber MES were 89% and 4.5mmol/(L∙d), respectively, significantly higher than that without any treatment. © 2019, Editorial Board of China Environmental Science. All right reserved.