Anaerobic digestion is a method of breaking down organic matter, such as animal or food waste, to produce biogas and biofertilizer. An anaerobic digester is a sealed, oxygen-free tank where this process takes place in the absence of oxygen. Anaerobic digestion is the natural breakdown of organic molecules by bacteria. “Organic” here refers to something that comes from or is manufactured of plants or animals. Whether the feedstock is food waste, animal manure, or wastewater sludge, all anaerobic digestion systems follow the same basic principles. Although the systems are designed differently, the process is basically the same. During the anaerobic digestion process, biogas is produced. When microorganisms break down (eat) organic materials without the presence of oxygen, biogas is produced (or oxygen). Biogas is a type of renewable energy that can be used in a range of applications.