We have five composting toilets. Composting toilets convert human waste into compost - usable soil. Wikipedia has a great article on the history of composting toilets and how they work. For our composting toilets, each toilet has two chambers. One is used for a year, then we switch to using the other side. The side which is not in use has intense microbial activity with the temperature raising to 77 C (170 F) as the material composts. Late in the composting cycle worms can be added for a cycle of vermicomposting. After a year, that side is ready to be emptied of its soil, which can be used on gardens. We use the compost on non-food gardens, but scientific data suggests the soil is perfectly safe for food gardens as well.
Before it's annual use cycle, the chamber is prepared with carbon-high grasses which grow natively in the forest. After every use a handful of oak leaves or sawdust is tossed into the toilet to balance the carbon and nitrogen and aid in the composting activity and in eliminating odors. Ventilation tubes also eliminate odors.
The major advantage of composting toilets is that useful water is not combined with human waste, which then needs to be sent to a centralized sewage treatment plant to be processed. Approximately 40% of normal household water is used just for flushing toilet. We use none.
Our composting toilet design is combined from two books as well as designs found online:
The Humanure Handbook: A Guide to Composting Human Manure, Third Edition
Composting Toilet System Book: A Practical Guide to Choosing, Planning and Maintaining Composting Toilet Systems
Our design is very simple because we have both space and time. For us, it is not necessary to have expensive composting toilets with fans and electricity.
Using collected old style water toilets we are building an art sculpture: The Shrine to the Outmoded Commode.
