Anaerobic biological treatment involves the decomposition of organic matter by anaerobic microorganisms in the absence of oxygen. This process is considered more sensitive than aerobic treatment. In recent years, research has focused on improving anaerobic reactor technology, particularly in enhancing biomass retention within the reactor to boost treatment efficiency. Additionally, there has been significant interest in optimizing biogas production and its use as a renewable energy source. These advancements are crucial for environmental protection, as they reduce greenhouse gas emissions while providing a sustainable alternative to traditional energy sources. In this chapter, we will present a concise history of biogas production technology and explore various anaerobic treatment methods designed to maximize biogas output. The chapter will also examine the characteristics of key substrates used in the process, describe the anaerobic digestion mechanism, and highlight the most widely adopted and promising technologies in this field.