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How Sun Mar Compost 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.
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.
use of this revolutionary Bio-drum results in composting speeds double
those of the old single chamber units with mechanical mixers.
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.
makes its units out of fiberglass 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.
There are three factors that determine the elimination of pathogens in compost. These are time out of the body, being consumed by higher bacteria which thrive in aerobic conditions, and, in electric units, being in a heated area which further sterilizes the pathogens.
The most crucial of these is the fact that the microorganisms which are classed as pathogens are usually a small enough microorganism that the higher, helpful bacteria in a compost consume them. When you cultivate an aerobic compost, as is done in a Sun-Mar, you make the compost a breeding ground for helpful bacteria such as bacillus subcillus and higher micro-organisms such as protozoa and rotifera that destroy pathogens through the food chain. These bacteria are the key ingredient in the Sun-Mar; they break down waste at a very fast rate while also killing pathogens.
The second factor, the times that bacteria live outside of the body in human feces, is a primary method of pathogen destruction in anaerobic composting (septic tank, etc.). Viruses are generally waterborne, and since the Sun-Mar toilets separate liquids from solids in the composting process in a Sun-Mar, the compost will never be at the saturation level where viruses may live, in addition to the fact that they would be "eaten" by higher, beneficial organisms if they did survive in the moisture level necessary to a compost. Most viruses, being parasites, cease to exist when they leave the body; if any do survive the change of environment, they generally do not live past a thirty day span. Remember, this thirty day span is without living in the unfriendly (for them) environs of a composting toilet. If you combine the hungry activity of aerobic bacteria and other higher micro-organisms with the short lifespan of a virus outside of the body, you render the pathogens down to almost nothing.
In the Sun-Mar electric compost toilets, pathogen destruction is aided by the introduction of heat in the compost finishing drawer. When the compost is in the finishing drawer, it is slowly "cooked" for the time that it is down there by the action of the heating element. This gives any surviving pathogens an additional enemy to battle; sterilizing heat. While the first two methods of pathogen destruction are enough to ensure that no harmful bacteria exist, the third, sterilization through heat, is extra insurance on the absence of pathogens in the finished compost.
The finished compost from our Excel model was tested in 1989 under NSF standard 41. The test done was the MPN, or Most Probable Number of coliforms test. This is the standard test for wastewater evaluation. The number of pathogens that came out in the finished compost was so small that no diseases or viruses could possibly be transmitted through the finished compost.
Under EPA Part 503, which regulates commercial compost, the acceptable coliform count is 1000 MPN. Commercial compost is sold to be spread in gardens and farming applications as fertilizer. 1000 MPN is already a very small amount of probable coliforms. However, NSF under standard 41 made the acceptable coliform count much lower, at 200 MPN. Under controlled test conditions, and even with the stress loading and power outage simulation that was put in place during the test procedures, our coliform MPN came out at the infitesimally small number of 27 MPN. While other composting toilet companies are trying to capitalize on the fact that their count was lower, the difference between them is so small as to be negligible. The finished product of the Sun-Mar toilet is safer to handle than most lake waters.
There is a mistaken assumption created by literature on humanure that compost toilets kill pathogens and compost the waste through thermophilic action (heat). A composting toilet will not provide enough heat through the mass of the compost to destroy pathogens thermophilically. Sun-mar toilets, as proven by the NSF test results, kill pathogens through mesophilic action, which is actually more efficient for our purposes and more rapid than thermophilic compost. Its bio-drum design is superior because it ensures aerobic action which encourages the beneficial bacteria. Aeration is of prime importance in creating an aerobic, oxygen-rich environment. This is why Sun-Mar toilets are, and always will be, the most efficient composting toilet on the market.
Sources: Bernhart, Dr. Alfred P. Evapo transpiration Nutrient Uptake Soil Infiltration of Effluent Water. Toronto: 1985.
NSF Report on Performance Evaluation Sun-Mar X.L Composting/Biological Toilet. Ann Arbor: July 1990.