Volatile Fatty\nAcid Production through Arresting Methanogenesis\nby Electro-Synthesized Hydrogen Peroxide in Anaerobic Digestion and\nSubsequent Recovery by Electrodialysis

Producing\nvolatile fatty acids (VFAs) in anaerobic digestion\n(AD)\nis of strong interest because of VFAs’ potential values in\nbiomanufacturing. Despite some success of VFA production via pretreatment,\nin situ inhibition of methanogens for VFA accumulation has yet to\nbe explored. Herein, a system consisting of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) production, application of H<sub>2</sub>O<sub>2</sub> for inhibiting methanogens in AD, and VFA separation was\ninvestigated. A polytetrafluoroethylene-based electrospinning electrode\nwas synthesized and capable of generating ∼4.2 g L<sup>–1</sup> H<sub>2</sub>O<sub>2</sub>. When the generated H<sub>2</sub>O<sub>2</sub> was applied to the AD, methanogens were inhibited, and VFA\naccumulation occurred. With the addition of 80 mg L<sup>–1</sup> H<sub>2</sub>O<sub>2</sub>, an average VFA concentration of 10.6\ng COD L<sup>–1</sup> was obtained. The long-term H<sub>2</sub>O<sub>2</sub> inhibition effect on methanogenesis was examined for\nnearly 100 days. A 2.3- to 3.3-fold increase in malondialdehyde levels,\nwhich indicated increased cell damage, along with a significant decrease\nin methane production and an increase in VFA concentration, might\nsuggest that H<sub>2</sub>O<sub>2</sub> could potentially inhibit\nmethanogens while allowing acidogenic bacteria to remain functional.\nThe accumulated VFAs were separated and then recovered using an electrodialysis\nunit, with a maximum VFA concentration of 26.7 g COD L<sup>–1</sup>. The results of this study will encourage further exploration of\nthe proposed system for VFA production by addressing several challenges,\nincluding a better understanding of the inhibition mechanism and a\nfurther increase in VFA yields.