Enhancement of the anaerobic digestion of nitrogenous substrate by implementing the approach of microbial electrolysis cell to force a microbial change

Anaerobic digestion is a natural biochemical process that can convert organic materials into combustible biogas. However, high ammonia levels can inhibit the process of methanogenesis and cause the failure of biogas production. For that reason, this study aimed to improve the stability and efficiency of anaerobic digestion in the presence of high ammonia concentrations and the production of biogas, through the implementation of microbial electrolysis cells (MEC) and direct interspecies electron transfer (DIET). The application of MEC to anaerobic digestion can accelerate the degradation of a substrate by enriching exoelectrogens and methanogens thus increasing biogas production. DIET has been recognized as faster and more stable means to transport reducing equivalents between bacteria and archaea, demonstrating the potential to enhance the rate-limiting steps during anaerobic digestion. The study was conducted with two independent experiments, one lasting 92 days and the other 34 days following the VDI 4630 and DIN 38414-8. Four reactors in each experiment were supplied with electrical energy, while two served as controls with no energy supply. The substrate used in the first experiment was aged, while the substrate in the second experiment had higher ammonia concentrations. The results suggest that the implementation of microbial electrolysis cells had a slightly positive effect on both experiments. However, these technologies did not significantly increase methane production compared to the control reactors.