Many composting toilets rely on controlled heat (either naturally generated by waste decomposition, or electrical/fuel-powered) and moisture to kill pathogens and break down waste in an odorless, aerobic process. Because excessive moisture and overuse (such as during parties or weekends with many visitors) can upset the microbial process, composting toilets on the market are now sized with specifications for "overload capacity" as well as regular use.
Maintaining composting toilets require control of:
- Temperature: Heat in the compost must be maintained for microbial function
- Moisture: Compost needs to be damp; however, too much moisture creating a soggy condition will inhibit aerobic activity
- Oxygen: Aeration needs to be ensured through turning or stirring
- Carbon to Nitrogen Ratio: Adequate carbon is important, as human waste is high in nitrogen. Carbon can be added with peat moss or kitchen vegetable scraps (no meat).
Examples of Large Composting Systems
These examples are not self-contained units; toilet seat must be located above the installed compost bin.
Clivus Multrum, Inc.
15 Union St.
Lawrence, MA 01840
Clivus systems are approved by the National Sanitation Foundation and can accommodate year round or part time use. They require on- site power to operate ventilation, moistening, and liquid removal pump systems. Waste retention time is four years, and waste treatment is accomplished with microbiological activity and Multrum Composting Worms (included). Compost material must be periodically removed from the bin. The specifications on the Clivus Multrum website assume a surrounding temperature of more than 65 degrees F, and recommend heat if temperature is lower. Liquid removed from compost must be disposed.
Cost: Model M1W/M2W (10-15 uses per day)$2,495 - $2,995; bin capacity is 248 US gallons; system includes waterless toilet seat; owner can purchase maintenance contract, or train for self-service.
EcoTech Carousel Composting Toilet
System EcoTech Composting Toilets
152 Commonwealth Ave.
Concord, MA 01741-3951
The Carousel system is a revolving cylinder divided in compartments for batch composting as they fill, and is certified by the National Sanitation Foundation. The system must be emptied periodically, from twice per year to once every four years, depending on use, and requires power to operate. According to the manufacturer’s website, wastes are reduced to 10% of their original volume.
Medium Bioreactor (four-person household, year round use, or 15 people daily for 60 days per year)
Cost: $2,700; exhaust system, $218-$382; toilet not included