The Clivus Multrum composting toilet shown in figure 17 is a continuous system and features a single chamber, in which combined processing of urine, faeces and organic household waste takes place (Del Porto and Steinfeld, 1999). The composting chamber is provided with a slanting floor, air conduits and at the lower end a storage space. A tube connects the toilet seat riser with the receptacle. There is a constant draught due to natural convection from an air intake in a vault, through which the air conduits, and out via a vent pipe. This system has a separate chute for the household organic waste. Because of the slopping floor, the content of the vault slowly slides down from the fresh deposits at the upper end to the storage part of the vault.

Figure 17: Clivus Multrum composting toilet (Source: Clivus Multrum)

The TerraNova composting toilet system of Berger Biotechnik, Germany is also a single chamber continuous system. Based on the Clivus Multrum, this system has been increasingly used in single family houses and ecological settlements in Germany (figure 18). In the ecological settlement Waldquelle near the city of Bielefeld there are about 70 systems in operation for single family and terraced houses as well as multi-storey buildings even up to the 5^th floor.

Another type of the composting toilet called twin-bin net composting toilet was used first time on the Pacific Islands (Del Porto and Steinfeld, 1999). It consists of two chamber constructed above the ground and inside each chamber a fishing net is suspended by hooks from the side of the chamber (figure 19 left). On the fishing net, a mat woven from coconut palm fronds is placed in order to separate the solid from liquids. The net also allows air to enter into the composting materials from all sides. In the chamber, coconut husks, small wood chops, leaves or vegetable food scrapes are added through the seat riser or drop hole periodically. The liquid that accumulates on the floor of the composting chamber is evaporated by air flow and wicks made from old clothing or is drained to an evapo-transpiration bed adjacent to the composting chamber. Air flow inside the chamber is provided with a large diameter vent pipe that draws air up through the pile from an intake opening located below the net along the rear wall of the vault.

Figure 18: Composting toilet in Eco-settlement Braamwisch, Hamburg

Figure 19: Twin-bin net composting toilet in the pacific islands (left) and Kerala double-vault toilet developed by Paul Calvert (right) (Source: Esrey et al., 1998)

In Kerala, India, the Vietnamese type double-vault composting toilet with urine diversion as shown in figure 19 (right) has been applied. Since most of the Indian people are washers, water used for anal cleaning is diverted along with urine to the evapo-transpiration bed. Over each vault there is a drop hole for faeces and a funnel for urine. Between the two vaults there is a trough over which anal cleaning is performed. The materials added for enhancing composting are straw, leafy material and paper scraps. A handful of ashes is sprinkled over the faeces after each uses.

Figure 20: Dryloo composting toilet (Source: Del Porto and Steinfeld, 1999)

Dryloo composting system as shown in figure 20 consists of a rotating PVC frame upon which six woven polyethylene bags are hung. These bags are used alternately and serve as faecal matter composter. It is placed in a watertight container just below the toilet stool. A fan and a vent pipe are provided in the system.

There are also other types of composting toilet systems either batch or continuous systems such as Minimus, Weelie Batch, Nature-loo and Rota-loo. They are increasingly used in Australia (Pollard et al., 1997).