The autonomous growth of Geobacter sp. dominated biofilms on electrodes and their sensitivity on volatile fatty acids (VFA) allows their application as biosensor. Here we report on the implementation of a microbial electrochemical sensor in the anaerobic digestion (AD) process. The amperometric sensor signal follows the acetate concentration profile in the AD process. Yet, the sensors stability is impaired by the process conditions. Therefore, potential biofilm inhibitors are individually examined, i.e., high salt and NH4+ concentrations as well as fumarate as potential alternative electron acceptor. The results show no influence of high salinity on the signal, whereas ammonia at a concentration ≥ 5 g L‐1 NH4+ acts as inhibitor and fumarate is used as substrate for current generation.