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Composting toilets are waterless (dry) toilets designed for use in applications with no plumbed sewage system. They operate on two principles:
The media would compost over time, but composting toilets are emptied regularly, even if infrequently. This means the media is actually not composting to any significant degree in the toilet. Some have argued a better term for this system is “dessicating toilet” but the name is not in widespread use.
While composting toilets are often vented by a fan, this is to remove moisture from the toilet rather than to control waste odors (which are negligible).
In general an RV-appropriate composting toilet is designed for use by 1-2 people. In this use the solids compartment is used for about 2 person-months. The liquids tank fills in a few person-days.
Normal 1-ply toilet paper is safe for the solids compartment though overuse can reduced capacity and over-dry the compost medium.
Commercial composting toilets are a sit-to-pee design for both sexes. The urine diverson systems are designed to work when sitting and keeping urine out of the solids compost is critical to the operation of the toilet.
Commercial composting toilets generally keep the solids container closed by a door when not in active use. There are two approaches:
There are several commercial models suitable for RV use. One can also make a simple DIY model.
Note: The C-Head's use of an inexpensive, cut-down 5gal bucket for the solids reduces costs but has some side effects the prospective buyer should consider: