This article discusses the startup phase of anaerobic digestion, co-digestion of sludge, and process parameters to maintain optimal range of desired variables. It covers the monitoring of parameters such as pH, temperature, alkalinity, volatile fatty acids, molecular hydrogen, total volatile solids, methane content, and total ammonia-nitrogen. The article also provides insights on the optimal substrate/co-substrate ratio for gas production. Subject: Biotechnology, Course Code: NA, Course Name: NA, University/College: NA