The primary goal of anaerobic digester monitoring is the establishment of system performance traits in order to avoid upsets and failure, while assuring reliable, efficient system operation with high levels of beneficial biogas (methane) generation. The discussions and recommendations provided in this document assume the most general, generic farm-based anaerobic digester operating situation where dairy operations are subject to change and changeable external organic feedstocks are accepted (co-digestion) potentially leading to system feed variations that could result in system struggles or upsets if proper monitoring and control were not provided.