Enhancing the CH4 yield of anaerobic digestion via endogenous CO2 fixation by exogenous H2

•H2 can be generated from anaerobic iron corrosion in anaerobic digestion (AD).•The generated H2 can be utilized for converting CO2 to CH4.•With CO2 fixation, enhancement up to 61% in the CH4 yield is achieved.•The added iron can also achieve phosphorus removal from the AD supernatant.

A large amount (25–60%) of degraded organics is converted directly to CO2 during anaerobic digestion (AD) process, which substantially lowers the energy (methane, CH4) yield. In this study, endogenous CO2 fixation by H2 from in-situ iron corrosion was explored to enhancing the CH4 yield. The results demonstrated that a substantial enhancement (up to 61%) in the CH4 yield could be achieved with both nano-scale zero-valent iron (NZVI) and waste iron scraps (WIS) being the added iron. Additionally, the added iron could also achieve effective phosphorus removal from the AD supernatant.