How Composting Toilets Work Working like the compost heap in the backyard, but odorlessly and much faster, Sun-Mar toilets break down human waste and toilet paper through the natural process of decomposition. Because most of this waste is evaporated, only a very limited quantity of finished compost is produced. Oxygen, moisture, heat and organic material are needed to allow minute natural organisms to transform the waste to fertilizing soil. Oxygen is provided by drum rotation and by the ventilation system.
Moisture is obtained directly from human waste.
Organic material in the form of peat moss is added manually, since this organic carbon is absorbent, holds oxygen, and is cheap and readily available. Microbes are contained in the rich top soil which is added to the compost. The engineered air flow within Sun-Mar units ensures that a partial vacuum is maintained within the unit at all times. Because air is continuously drawn into the toilet, there is no backdraft, and hence no smell. In addition, the tumbling action of the composting drum results in such a moist and beautifully oxygenated compost that an aerobic breakdown takes place which is both fast and odorless.