Composting toilets are well-ventilated containers that contain and control composting of excrement, toilet paper, carbon additive and food wastes with little or no water. The system relies on unsaturated conditions (i.e., the material cannot be fully immersed in water), where aerobic bacteria and fungi break down wastes, similar to that of a yard waste composter. The main objective of composting toilet systems is to contain, immobilize or kill organisms that can cause human diseases without contaminating the immediate environment and harming its inhabitants.
Sometimes called biological toilets, dry toilets and waterless toilets, these toilet systems can break down wastes to 10%–30% of its original volume when properly sized and operated. The end product is called ‘humus’ – a stable soil-like material, which must be either buried or removed according to existing regulations.