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Liquid drainage

Evapo-transpiration trench(See Figure 8.5)
The purpose of the evapo-transpiration trench is to ensure that excess liquid that is drained from the toilet does not reach the surface or contaminate the ground water. This is achieved by:

  • sizing the trench such that the probability of surcharging is very low;
  • planting the top and adjacent areas with species that will maximise evapo-transpirati from the trench.
  • bunding and raising the trench to prevent surface run-off into the trench and to maximise rainfall run-off from the top of the trench.

Figure 8.4 Composting toilet used in Kiribati

Figure 8.5: Evapo-tranpiration trench

Food crop trees, such as papaya, banana or breadfruit can then be planted adjacent to the trenches to further assist evapo-transpiration. Plants or trees which provide bulking agent could also be planted on trenches.


The approximate unit cost of the locally built composting toilets on Kiritimati including the toilet building based on the specified design is AUS$2,500 to AUS$3,000. This includes all materials, I-Kiribati labour costs and the liquid drainage trench requirements.


From the results of the education component in the sanitation pilot on Kiritimati, it is recommended that an incentives package be offered to encourage the widespread acceptance and use of the composting toilet on the island and to effect an understanding of the direct relationship between sanitary habits, water quality and hygiene, and the connection with health and nutrition. This package should include a well fenced garden area, seed, trees and plants and gardening assistance and advice. This strategy may not be an effective educational tool in some other cultural context, and community feedback will indicate which strategy is most appropriate in each application. What can be undertaken is, of course, also dependent on available funds and resources.

Results of the trial

The sanitation project was conducted from June 1994 to September 1995, to ascertain whether the composting toilet was appropriate to Kiritimati from a cultural, technical and environmental point of view. An appraisal team of four consultants visited the island to assess the trial in September 1995. The prefabricated toilets had been trialed for ten months and the locally built units were trialed for 3 months prior to the appraisal. The trial project team recommended that this was much too short a trial period to fully cover all the issues involved. However there was considerable pressure to proceed with the long delayed Water Supply project and now that it entailed a sanitation component it was necessary to proceed with the larger Water and Sanitation strategy as soon as possible. A survey was conducted and 258 households out of 316 said they would like a composting toilet. It was decided that the 'pilot' trial had been sufficiently successful to justify an extended trial of some 200-300 composting toilets with the intention that the whole island would eventually be using composting toilets.


Usage of the prefabricated toilet during the 10 months that the Wheelibatch and Cage Batch toilets were trialed usage slowly increased in the domestic applications. Given the number of people in the households it was obvious from the rate at which the bins filled up that only a percentage of the household were using the toilets in the early stages. The women were more inclined to use the toilets as they offered some privacy. Teenage boys reported that they were embarrassed to be seen entering the toilets. The men preferred to use the bush or the beach. After the video was shown throughout the community, usage increased. Toward the end of the trial some families reported that everyone was using the toilet including the men. The gardening program resulted in a significant increase in the trial participants' interest in the composting toilets.

Usage of locally built toilets was much more consistent from the outset. It appeared from the rapid rate at which the bins filled up that all household members were using the toilet. This may have been due to the more integrated design and it may also have been due to the toilets being within the non-government village and being built by village residents.

At the schools, the usage was consistently low for a number of reasons. The toilet was rather conspicuous and the children were sometimes teased for using it. The teachers insisted on locking the toilet so the children had to ask the head teacher for the key. As many of the children have chronic diarrhoea this would have been a demanding requirement. Most of the teachers did not use the compost toilet but continued to use flush toilets in the teachers nearby houses, which would not have provided very encouraging example to the children. The teachers became more interested in the composting toilet through the gardening program. It is thought that when a greater number of people have composting toilets at home the children will feel less conspicuous using the toilets at school.

Cultural issues

Taboos related to sorcery and faeces were a concern with regard to containing excrement in a bin that may be accessible to prohibited persons. Certain taboos relating to menstruating women using the toilets were also raised. However these issues did not seem to be a problem within the family and as the trial progressed, people became more comfortable using the toilet regardless of these concerns. At the outset of the trial, there was a definite aversion to the prospect of using the end product for fertiliser or any other method of disposal that might allow contact. It was difficult for people to believe that excrement would be transformed into an acceptable material. However when the piles in the toilets did actually produce compost there was a relieved and surprised response, and a marked increase in interest in the toilets. Neighbours to trial participants, who had previously been disinterested or even hostile to the project, requested a composting toilet because they wanted to be able to have a garden and use the compost as a soil improver.

People objected to the height of the buildings. They said they felt uncomfortable using a toilet, which was elevated, above ground. Some said they feared that a person may be underneath. This probably relates to the traditional use of latrines that are suspended over water. The height of the buildings caused embarrassment to some people because they were conspicuous when they climbed the stairs and used the toilet.

A request was made by householders that the toilet doors be made lockable in case strangers used their toilet. However most people lost their keys within a short time and so the toilets then remained unlocked, except for the schools and the clinic.

During the reconnaissance trip in June 1994, the community was asked whether they would prefer squat plates or pedestals for the toilets. Most people replied that they would prefer pedestals but it was indicated that in fact many people would still wish to squat, so a compromise was made by designing a low pedestal which allowed sitting in a semi-squatting position. The pedestal was also made strong enough to support considerable weight for squatting on the seat if desired.

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