Biogas is a type of biofuel that is naturally produced from the decomposition of organic waste. When organic matter, such as food scraps and animal waste, break down in an anaerobic environment (an environment without oxygen), they release a blend of gases, primarily methane and carbon dioxide.  Because this decomposition happens in an anaerobic environment, the process of producing biogas is also known as anaerobic digestion.

Anaerobic digestion is a natural method of waste-to-energy that uses the process of fermentation to break down organic matter. Animal manure, food scraps, wastewater, and sewage are all examples of organic matter that can produce biogas by anaerobic digestion. Biogas is combustible and therefore produces a deep blue flame, and it can be used as an energy source.