About UNEP
United Nations Environment Programme
Division of Technology, Industry and Economics
top image
space space space
Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

The compost and hygiene

To keep the composting toilet system simple and sustainable it is important that the end product can be disposed of by the users within the house site. Therefore the compost should be free of disease causing organisms. Testing the compost reveals how effective the composting process has been within a particular time frame, and indicates guidelines for usage.

Six of the toilets were ready to be emptied of compost during the September 1995 visit. The compost in each case had the appearance of decomposing bulking agent (whichever leaves or fibre had primarily been added to the toilet during use) and had a pleasant humus odour.


To maintain the composting process, it is preferable that a small handful of bulking agent such as dry leaves or coconut fibre be deposited in the toilet after defecation to allow a suitable mix of material containing nitrogen and carbon. If people forget to add the bulking agent, the pile will eventually smell unpleasant. Usually if a quantity of leaves is then deposited in the toilet, the smell disappears.

As many housewives in Kiritimati sweep up leaves around the house each day and burn them, it was not too difficult for them to collect enough leaves to have a ready supply by the toilet.

When the bin that is being used is full, it is simply a matter of unscrewing the pedestal and changing it over to the side of the empty bin. The toilet can also be designed to have a pedestal or squat plate over each bin so there is no need to make a change. However changing the pedestal and closing the first bin ensures that no one will mistakenly use the bin that is now undergoing a fallow period.

When the fallow period is complete the compost can be shovelled out of the bin and mulched around fenced fruit trees. If the trees are not fenced, pigs and chooks will dig up the compost and scatter it around.

The pedestal rarely requires cleaning as it is low and splayed to avoid material collecting on the inside. If the seat becomes dirty it can be wiped with wet leaves or rags and then these can be dropped into the toilet.

As Kiribati women are responsible for sanitation in the home, all the above chores were conducted by the female head of the family, without any apparent difficulty. Most women reported that it was easier than looking after a water based toilet.

It would be unusual for the drain to become blocked as solid matter is filtered through the false floor at the base of the bin. However, if necessary, the pipe to the trench is approximately half a meter long and could be cleared with a stick through the access point.

Material for repairs to the building frame or the concrete bins would be available on the island. There is little else that requires maintenance in this alternating batch composting toilet design.


The introduction of composting toilets requires considerable input from local personnel skilled in a health education and community consultation probably over 2-3 years. Curriculum Development Officer to work with teachers and students in the schools on water quality and sanitation issues would be most useful at the beginning of the project. For government housing a Sanitation Officer responsible for basic maintenance of toilet structure and on-going advice as to usage of the toilet and the compost would need to be on call in the same way as a plumber would be readily available for attention to waterborne systems. This person should receive remuneration that reflects his or her essential role in the community to counteract any negative association attached to people who take care of toilets. For long term residents in non government housing most maintenance issues could be handled by the householder once they have been exposed to the initial education program, and are in the habit of using the composting toilet.

If composting toilets are initially to be introduced by expatriates it is important to include both female and male team members. Implementation will depend primarily upon the co-operation of the women in the community, and sensitive issues are more effectively discussed between persons of the same gender. Initiating the gardening program should be undertaken by a person with cultural awareness and good people skills in addition to having experience with the hygienic use of human excreta in cultivation, and small plot gardening in physically antagonistic circumstances.

Water Based Sanitation Systems

A centralised sewerage system was installed in Tarawa the capital of Kiribati and some maintenance and pollution problems have been experienced as a result. Pits, aqua privies and septic tank toilet systems have also been installed with the assistance of aid donors and used on Kiritimati for many years. It is often considered to be an indication of status to have a flush toilet in the house. Health education programs have been conducted throughout Kiribati over the last 40 years to deter people from using the traditional location of the bush and the beach for defecation, and to use a water based toilet or pit latrine instead. In some places people have been fined a dollar if they were caught using the beach and their excrement was not immediately removed by the tide. I-Kiribati initially found the water based toilets unacceptable for a variety of reasons but over time and with the persistent efforts of community heath educators the flush toilets have been accepted and increasingly desired by the I-Kiribati. It is therefore a very difficult adjustment to be now told (once again by outsiders) that water borne sanitation systems may be contributing to the high incidence of enteric disease on the island and that a practice that was advocated as a health measure may be a cause of ill health. It is understandable that the composting toilet trial has been viewed with considerable wariness and scepticism, and technology transfer must be conducted with caution, patience and some degree of humility.

In the case of the aqua privy and the septic tank system the effluent from the toilet is discharged directly to the ground water. The septic tank if well maintained provides primary sedimentation but in any circumstances does little to reduce pathogens, BOD or nutrients in the effluent. Berg et al. (1976:: 175) suggests that primary sedimentation will not remove viruses at all, and if such effluent is chlorinated will only remove 50% of viruses. If the septic tank is not emptied when necessary then solids will also overflow into the leachfield. The truck used for emptying septic tanks has been out of action for some time on Kiritimati so the residents either allow the tank to overflow or empty the tanks by hand and dispose of the sludge nearby, or in the lagoon. The appropriately sized horizontal trench that can ordinarily provide some treatment of the effluent from septic tank is not used in Kiribati because of the highly porous soil and the inclination to flooding in the rainy season. The leachfield is instead a vertical funnel that facilitates direct drainage to the ground water. As water borne enteric diseases such as Giardiasis are very common on Kiritimati, it is likely that reinfection is maintained partly through contaminated water. However, this has not been empirically proven. Transmission of disease would also be caused through not washing hands after defecation and from flies that come in contact with exposed faecal deposits.


Thorough research and development of mesophilic composting toilets for application in a variety of resource constrained circumstances in the developed and developing world is a relatively recent phenomena. This study is certainly not presented as the final word on the subject. It is hoped that the technical and educational developments that have occurred to date will be expanded upon by those most suited to do so, that is, the individuals and communities that use the toilet, and adapt it to their own needs. Although the composting toilet is strongly recommended as a simple sustainable sewage treatment option it is not the intention of the author to be a technological missionary on this issue.

While advocating due consideration of composting toilets it is not implied that centralised sewerage systems or on-site water borne methods such as septic tanks or pourflush latrines do not have a valid role. It is rather to suggest that in any country, the most appropriate technology should be applied in each location, and that the selection from a range of equally accessible technical options should be based on a thorough appraisal of the cultural, socio-economic and ecological context to be serviced.

NOTE: An Australian funded project constructing composting toilets on Kiritimati is currently being implemented. Thus the suitability of composting toilets on Kiritimati will not be know for another year or two.


      Main Menu


  • Brochure
  • IETC Brochure

  • International Year of Forests
  • International Year of Forests

  • World Environment Day
  • ??????

  • UNEP Campaign
  • UNite to Combat Climate Change