Study of a Pilot Scale Microbial Electrosynthesis Reactor for Organic Waste Biorefinery

Microbial electrochemical technologies now enable microbial electrosynthesis (MES) of organic compounds using microbial electrolysis cells handling waste organic materials. An electrolytic cell with an MES cathode may generate soluble organic molecules at a higher market price than biomethane, thereby satisfying both economic and environmental goals. However, the long-term viability of bioanode activity might become a major concern. In this work, a 15-L MES reactor was designed with specific electrode configurations. An electrochemical model was established to assess the feasibility and possible performance of the design, considering the aging of the bioanode. The reactor was then constructed and tested for performance as well as a bioanode regeneration assay. Biowaste from an industrial deconditioning platform was used as a substrate for bioanode. The chemical oxygen demand (COD) removal rate in the anodic chamber reached 0.83 g day(-1) L-1 of anolyte. Acetate was produced with a rate of 0.53 g day(-1) L-1 of catholyte, reaching a maximum concentration of 8.3 g L-1. A potential difference (from 0.6 to 1.2 V) was applied between the bioanode and biocathode independent of reference electrodes. The active biocathode was dominated by members of the genus Pseudomonas, rarely reported so far for MES activity.