Anaerobic digestion (AD) is a natural biological process. While there are many kinds of digesters, the biology is basically the same for all. Anaerobic digesters are built systems that deliberately harness the natural process. Anaerobic digestion (AD) systems can minimize odors and vector attraction, reduce pathogens, produce gas, produce liquid and solid digestate, and reduce waste volumes. Anaerobically digesting organic carbon involves naturally occurring bacteria. Digestion
takes place when organic materials decompose in an oxygen-free environment. Some digester systems differentiate between “wet” and “dry” digesters, or low-solid and high-solid systems, and sometimes the process is called fermentation. During digestion, various microbes use the organic matter such as animal manure, sewage sludge, wasted food and other organics in the absence of oxygen. The process can be controlled and enhanced through chemistry and engineering.