Some toilets use earthworms to decompose faecal matter and kitchen organic waste (figure 21). The Dowmus system in Australia is partially filled with active compost at the time of installation and inoculated with beneficial soil organisms in particular tiger and red composting worms (Ho and Mathew, 1998). There is no heating element and the system is not intended to operate above 35 °C, to protect the worms. The process depends more on soil organisms and worms rather than on the thermophilic microorganisms for composting. It can also take other household organic matters provided they are cut into small pieces.

Figure 21: Dowmus composting system with worms (Source: Dowmus)

A Vermi-processing toilet has been field tested for 8 years in India and was found to be a novel low water-use toilet for safe processing of human excreta without odour and fly problem. It is started off by putting 5 kg of vermicastings in the pit. The operation of the toilet employing the pit is very simple and hygienic as the human excreta will be completely converted to vermicastings (Bhawalkar and Bhawalkar, 1991). In the USA, Redworm (Eisenia and Lumbricus rubellus) has been added in the Clivus Multrum composting toilet (Rockefeller, 1995). Because of low moisture in the toilet, daily misting with water is required for maintaining optimal moisture content. The effect of redworms on the degradation process in the toilet has been remarkable. Most of the faecal matters and kitchen wastes were flat, worm castings covered the entire surface. Recently, the Dowmus vermifiltration system has been developed for domestic wastewater and kitchen organic waste treatment in Australia (Bajsa et al., 2002). This system has a composting tank from which the liquid is drained. Vermicomposting is used for the treatment of the tank contents. However, since ammonia is sensitive to worms, urine should be diverted.