The type of toilet described is based on the method of disposing of the sewage, and related requirements for the structure and other aspects of construction such as ventilation, washing facilities and so on. There are five possible options for sewage disposal, as follows.
In these the toilet seat is set above a box or hole into which all sewage accumulates. If the moisture content can be kept reasonably low, for example by the addition of soil, ashes or bark, then the material breaks down into a relatively odour-free compost, which can be emptied from sewage receptacles at the back of the toilet building and safely disposed of in a suitable location.
There are various proprietary makes that have developed this type for relatively low-use sites. Plastic containers prevent contamination of groundwater. Special bark is put into the toilet after use by the user, which reduces the odour and helps the process of composting. No water is required, and the unit can be constructed above ground. This is important in areas where groundwater is sensitive to pollution, where the ground is rocky, or where it becomes frozen in winter, so making holes difficult to dig.
These toilets are common in Scandinavia and are increasingly available in North America, where proprietary systems have been