What is the term to digest in absence of oxygen?

The term for digestion in the absence of oxygen is anaerobic digestion. This process occurs in certain microorganisms, such as bacteria and archaea, that can break down organic matter without the presence of oxygen. Anaerobic digestion is commonly used in wastewater treatment plants and biogas production facilities to convert organic waste into biogas, a mixture of methane and carbon dioxide, which can be used as a renewable energy source.