Composting Toilets

Current system in use at Crag Camp, Gray Knob and The Perch

Composting Toilet DiagramThis toilet system recycles human waste. The aim of composting technology is to optimize conditions for microbial activity. By enhancing the living conditions within the compost tank for natural oxygen-using microbes (aerobes) which use human waste as a food source, the waste decomposes over time into a soil-like substance. The process of transforming raw waste into finished compost results primarily from soil microbes such as bacteria, fungi and actinomycetes. Soil invertebrates such as springtails, mites, millipedes and beetles also contribute to waste decomposition. Disease-causing organisms (pathogens) within the human waste are reduced or eliminated due to the presence of oxygen and as a result of the competition between organisms, natural antibiotics, the loss of nutrients and heat.

The essential ingredients of a compost pile are organic material, microorganisms, moisture, oxygen and heat. As air enters the tank and the aerobes consume nutrients, the volume of the waste pile is reduced as some of the mass is converted to carbon dioxide and water vapor. Adding wood chips increases the amount of organic material or carbon, absorbs moisture and odors and provides air space and structure within the pile. In order to maintain consistent input, only the RMC caretaker adds the wood chips. Unlike many composting toilet systems, it is all right for users to urinate into this system. Garbage interferes with the composting process and must be removed by the caretaker.

The toilet seat is situated over a sealed container where the waste is stored. Within the chimney is a fan powered by a solar (photovoltaic) panel. The fan draws air through the system during daylight hours. The waste is suspended above the bottom of the tank on a perforated liner enabling air to circulate above and below the waste pile. The box around the compost tank is stained black to absorb heat from the sun. The pile is mixed periodically to increase the amount of oxygen available to the aerobes. Fresh waste is pushed to the back of the tank and older compost settles towards the front. After several years, a portion of the compost can then be removed and safely disposed of on-site, spread among low growing vegetation during the spring and summer.

History of the Crag Camp Bio-Sun Toilet

Behind the Bio-Sun composting toilet at Crag Camp.The facility has used a variety of methods in the immediate area for the disposal of human waste. During the warmer months, waste was collected in a 60 gallon container situated beneath the outhouse structure. The waste was emptied and composted in bins periodically. In order to keep liquid content down, users of the composting toilet were asked to urinate in the nearby woods. Large amounts of wood shavings were needed to adequately compost the waste. Crag Camp also used a pit toilet for the collection of waste in the winter. The pit was dug out in the spring and then actively composted.

In 1994, the RMC determined that as a result of the following factors, 1) the number of visitors at Crag Camp, 2) the fragile alpine environment nearby, 3) the potential increase in use of the facility, and 4) the condition of the current toilet system, and improved waste treatment system was needed. The research following this decision was completed by RMC caretakers Paul Lachapelle and Paul Neubauer with the help of RMC Vice President Doug Mayer.

All possible scenarios concerning waste disposal were considered including incineration, chemical treatment and fly-out. The decision to compost the waste on-site and purchase this particular system was based on conversations with USFS representatives, people involved in backcountry toilet maintenance and manufacturers of toilet systems. Overall, it became clear that the continuous composting technique is an effective waste treatment method and that continuous composters are functioning well in many diverse environmental settings, including sites comparable to Crag Camp.

The system at Crag Camp works essentially as a containment device as ambient temperatures approach freezing. The compost pile reactivates when temperatures consistently average 40°F or higher (May to October). The RMC has oversized the composting system due to two key factors. First, the system will actively compost for only four months out of the year due to the low ambient temperatures. Second, high relative humidity may slow the composting and evaporation process. The RMC wants to insure that the system is a long term solution to waste treatment, therefore, over-sizing the unit will safeguard against the possibility of an overflow situation.

The RMC appreciates your interest in our composting toilets. If you have any questions, please e-mail us. We would like to thank the Appalachian Trail Conference, L.L. Bean, the Davis Conservation Foundation, the U.S. Forest Service and RMC members John Tremblay, Paul Neubauer, Paul Lachapelle, Bill Arnold, Ray Cotnoir and Doug Mayer for their contributions towards this project. This toilet system is manufactured by Bio-Sun Systems Inc., Millerton, PA (1-800-847-8840).

The Bio-Sun composting toilet at The Perch.

Related Links

How to Contact the RMC
Bio-Sun Systems Inc.