Application of the Single-Stage Process of Dark Fermentation and Microbial Electrolysis to Improve Hydrogen Productivity from Water Hyacinth

Abstract

The production of hydrogen (H2) from water hyacinth (WH) can contribute to reducing both the negative impact of WH on ecosystems and dependence on fossil fuels. In this study, the combination of dark fermentation (DF) and microbial electrolysis cell (MEC) in a single reactor, namely, sDFMEC, was investigated to improve the H2 productivity of WH. Furthermore, the intermittently applied voltage (I-Eapp) scheme and various methane (CH4) inhibition methods, including air exposure, heat treatment, and chloroform (CHCl3) addition, were applied for performance enhancement purposes. The findings indicated that with a sufficient duty time of external energy input (less than 1 hour), the intermittent mode can enhance the performance of WH-fed sDFMEC but does not significantly inhibit CH4 formation. While air exposure and heat treatment damaged both methanogens and exoelectrogens, lowering sDFMEC performance, additional CHCl3 showed the best selective and long-term inhibition on methanogens (over 350 operation hours without further addition). Overall, the combination of the I-Eapp scheme and CHCl3 applied in WH-fed sDFMEC achieved a yield of $670.1\pm 15.2\text{mL}-{\text{H}}_2/\text{g}-\text{VS}$ , around 160% higher than the normal condition.