There is a limited, but expanding, market for these toilets. With an emphasis on the environment, easy installation and space saving, the initial cost is relatively high compared to a cassette unit. The idea of composting toilets has been around a long time but relatively slow to catch on in the boating market, mainly as they have been designed for domestic use first and foremost.
Benefits however include no chemical use and a substantial water conservation. They are a stand-alone unit so no plumbing is required, the only connection being a 12VDC supply for a low (<1amp) consumption power supply for an aerating fan. Even this can be dispensed with for an appropriately sized solar powered vent.
These units mimic a household unit in terms of the lid and seat so there is less emotional stress when moving between the two! Composting toilets are also marketed as being ‘odour free’.
These toilets work by separating solids from liquids. Urine is deposited into a receptacle which can be detached and emptied when full in to a standard sanitary station, or used as a fertiliser (diluted 1:8) if you have permission on nearby land. Solid waste is collected in a paper bowl liner and flushed without water into a composting tank below the bowl. The composting tank has a quantity of peat moss into which the solid waste is turned by an externally mounted handle. The solid waste is the same consistency as soil once dried and you can bag it and bin it in normal household rubbish bins.
One manufacturer claims 80 uses before the solids tank is full and two days on the liquids tank for an “average” couple. Another manufacturer claims a couple living aboard should last 3 months without emptying the solid matter.
Some of these units can be hooked up to a pump-out storage tank should you require extra long periods between empties.
The next step on from a composting toilet is then a folding toilet made out of a cardboard box i.e a disposable toilet. These are a great idea for a ‘spare’ on-board but also for camping, festivals etc. A manufacturer claims even though it is literally a cardboard box, it will take the weight of a 16 stone person. This is a great back up device on board for when you are not able to reach a sanitary station or frozen in and unable to move to the pump out.