Anaerobic processes are biological reactions that occur in the absence of oxygen. These processes are essential for breaking down organic matter, allowing microorganisms to convert sugars and other compounds into energy. Common examples include fermentation and anaerobic respiration, which are utilized by various bacteria and archaea. In anaerobic digestion, organic waste is decomposed by microorganisms, producing biogas, which mainly consists of methane and carbon dioxide. This biogas can be harnessed as a renewable energy source. Anaerobic processes play a crucial role in natural ecosystems and are also applied in waste management and energy production.