Numerical modelling of interspecies electron transfer in anaerobic digestion using multiple electron donors for methane production

Abstract

Direct interspecies electron transfer (DIET) is an efficient approach to enhance methane production in syntrophic metabolism during anaerobic digestion; yet a quantitative understanding of DIET mechanisms between exoelectrogens and electrotrophic methanogens is still lacking. This study presents a novel diffusion–reaction multi-physics model to simulate interspecies electron transfer between rod-shaped exoelectrogens and spherical electrotrophic methanogens for the first time. The numerical results indicate that the electron transfer rate in DIET are 5.6 to 8.8 times higher than that in interspecies hydrogen transfer (IHT). The increase of substrate concentration (0.001 − 0.1 mol/L), nanowire conductivity (0.1 − 50 Ω⋅m), nanowire number (1 − 1.0 × 104) and redox cofactor number (10 − 1.0 × 104) significantly enhance electron transfer of DIET in syntrophic metabolism. Furthermore, the presence of conductive material can increase the electron transfer rates of DIET by up to 56.6–85.1 times compared to the control group. This study provides new insights into the optimization of DIET in the anaerobic digestion of organic wastes, offering a quantitative basis for improving methane production through targeted manipulation of system parameters.