Anaerobic digestion (AD) technology has been widely applied globally. AD not only relieves the shortage of energy in rural areas but also effectively reduces the environmental pollution caused by the improper management of agricultural waste. Chapter 5 presents a comprehensive overview of seven aspects of the development of AD: (1) the concept of AD development, (2) potential of biogas production and recovery, (3) industries using anaerobic digesters, (4) current barriers to AD deployment, (5) application of ruminal microorganisms and other microbes for AD, (6) modeling microbial diversity in AD using various models, and (7) kinetic modeling and the evolution of synergistic impacts during AD. This material will be helpful for understanding the history, classification, mechanisms, applications, and future prospects of AD.