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. Heat is generated by the compost itself, assisted by the heating element ( on electric models). 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. Breakdown is odorless because aerobic microbes produce only carbon dioxide and water vapor, quite unlike the unpleasant anaerobic smell often found in a septic tank, outhouse, or backyard compost.

Microbes and the BIO-DRUM: Sun-Mar's unique Bio-drum has been developed to provide the optimum conditions for aerobic composting. Using a Bio-drum, Sun-Mar has been able to ensure that the compost in the drum is maintained in the moist, warm, well mixed, oxygen rich condition which aerobic bacteria need for optimum performance.

Sun-Mar has also found that the use of a Bio-drum avoids the anaerobic activity which occurs wherever there is insufficient oxygen. This is important because anaerobic activity is slow and produces offensive odors.

The use of this revolutionary Bio-drumTM results in composting speeds double those of the old single chamber units with mechanical mixers.

Start up and Use: Sun-Mar units require very little maintenance. Peat moss should be added at the rate of one cupful per person per day. Toilet paper is decomposed easily by Sun-mar units and should be added as usual. The compost should be mixed and aerated every third day (or at the end of the weekend) while the toilet is in use, simply by turning the drum handle and rotating the drum 4-6 complete revolutions. In cottage use, some composted material may only need to be extracted in the spring. In residential or commercial use extraction will be more frequent.

Winter Use: Sun-Mar makes its units out of fibreglass and marine grade stainless steel, so freezing temperatures will do no damage even if the compost freezes in the drum. Composting action decreases with temperature, so for extended winter use, the unit should be kept at a minimum temperature of about 55-60 degrees F (13-15 degrees C) and all piping should be well insulated. For periodic use in winter, the toilet may be used as a holding tank, until the compost warms up, and the microbes emerge from dormancy. Electric units should be plugged in on arrival so the ventilation system is working and there will be no odor. When the compost is frozen, the drum should not be rotated.