Biodigestion (also called anaerobic digestion or AD) operates in the absence of oxygen usually in a sealed, contained area. Bacteria decompose the organic matter, producing a biogas (methane and carbon dioxide) that can be captured to produce energy. After left over liquid (leachate) is removed, it can be processed into a fertilizer. The finished solid matter (digestate) is a productive soil enhancer. It can also be added to a compost system as a starter or to further minimize pathogens by putting the matter through a second process.
Biodigestion works in a multi-million-dollar plant producing energy or in a simple do-it-yourself in-ground septic system.
Biodigestion units using dog waste have lit gas lamps in Cambridge, Massachusetts (U.S.) and Malvern Hills (U.K.) projects.