Compost toilets are not common in the UK as we are lucky enough to have a comprehensive mains water and sewage system. But compost toilets can still be useful for properties without access to a main sewage system, for use at outdoor events and as a water saving measure. 30-40% of household water use is for toilet flushing so water saving would be a big benefit.
Compost toilets are basically a dry toilet with no need for water. Most are of the dual chamber variety whereby one chamber is fitted with a seat and is designed to fill after approximately one year. At the end of that time the seat is transferred to the second chamber while the first is sealed in order to allow the composting process to continue. By the end of the second year the contents of the first chamber will be ready for use as compost.
Perhaps surprisingly, compost toilets shouldn’t smell providing that they have an air vent and a ‘soak’ such as sawdust or straw is used after each use. This soaks up excess moisture and assists in the composting process. The compost at the end of the process looks and smells very much like the compost you would buy at the garden centre, although it is usually recommended that it is not used on foodstuffs.
Converting an existing toilet to a compost toilet is probably not cost effective, but it would be comparable in price to install compost toilets in place of conventional on-site drainage for rural new-build projects. If the reason for installing a compost toilet is mainly due to the lack of mains sewage, greywater recycling will also be necessary.
For more information on compost toilets visit the Environment Agency website.
