 anaerobic digestion is a process in which microorganisms break down organic matter in the absence of oxygen. Small-scale household biogas digesters are designed to convert organic waste into biogas, which can then be used for cooking, lighting, and electricity. These digesters come in various sizes and designs, with the most popular being the fixed dome, floating drum, and plug flow types. The pH, temperature, substrate, loading rate, hydraulic retention time, HRT, carbon 2, nitrogen ratio, and mixing all play a role in determining how well the digester works. Additionally, the government has implemented policies to encourage the use of household biogas digesters, while their social and environmental benefits have been widely recognized. This article was authored by Muhammad J. Tahirzadeh, Salmaz Aslanzada, and Karthik Rajendran.