Anaerobic digesters in the form of a garage in which drier organic material is digested. Commonly there are a minimum of 3 digesters next to each other to allow a semi-continuous batch process. One digester is loaded with fresh organic material, in the second digester organic material is already producing biogas for half of the retention time, while the third digester is almost ready to be unloaded as most of the biogas has been extracted already.
