Newsletter and Technical Publications
<Sourcebook of Alternative Technologies for
in Small Island Developing States>
PART C - CASE STUDIES
5.4 Composting Toilet Trial on Kiritimati, Kiribati
In June 1995, a trial of composting toilets was initiated and funded on
Kiritimati, Kiribati, by the Australian Government. The trial was
conducted by a multi-disciplinary team from the Centre for Environmental
Studies at the University of Tasmania, in co-operation with I-Kiribati
counterparts, as one of several trials of composting toilets in the
Pacific region. Other trials included a project conducted by Greenpeace in
the Federated States of Micronesia (FSM), during 1992 and 1993, which
involved the installation of two commercially-available designs and one
locally-built composting toilet; and, the recent installation of 30
toilets, using 3 different commercial designs, on the Torres Strait
islands (between Australia and Papua New Guinea). The Greenpeace trial in
the FSM involved extensive community consultation at the implementation
stage, while the Torres Strait trial had little community participation.
However, neither of these projects resulted in the expanded use of
Figure 41. Line Islands, Republic of Kiribati, showing
the location of Kirimati.
Kiritimati (Christmas Island) or Abakiroroa (Faraway Island) is a coral
atoll in the Line Islands, Republic of Kiribati. Kiribati is a small
island nation of 33 coral islands dispersed along the Equator in the
Central Pacific. There are three groups of islands and atolls, and
Kiritimati is the southernmost atoll in a chain of islands known as the
Northern Line Islands (Figure 41). Kiritimati is the largest coral atoll
in the world, with a land area of 320 km2, and a total area of 640 km2,
including a central lagoon, and many other lagoons, most of which are
landlocked and hypersaline. Kiritimati has a highly variable rainfall
pattern with an average of about 860 mm per year. The present population
is approximately 3 000 people living in five villages: Banana, London,
Poland, Main Camp, and Tabakea. Most of the I-Kiribati residents,
except in Tabakea, are families of government employees. The land on the
island is owned by the government of Kiribati.
Water supply is provided from rooftop catchments or drawn from the
groundwater (from freshwater lenses) by the use of wells, and there is
some reticulation (see also Part C, Case Studies). The limited number of
rainwater tanks is due to the erratic rainfall and long periods of
drought. Groundwater is pumped from infiltration galleries constructed to
skim freshwater from the top of the lenses. Deterioration in the quality
of the groundwater has occurred through localised overpumping of the
lenses. The groundwater is also affected by bacteriological and chemical
pollution from human activities, particularly domestic pigs and dogs,
latrines and septic tanks, greywater soakaways, fuel storage facilities,
agricultural activities, and open rubbish and Babai (taro) pits .
The locally-built, dual-chamber batch composting toilets, shown in
Figure 42, are characterised by two adjacent cubic chambers, approximately
1 m square on the sides, the top of which forms the floor of the toilet
building; a pedestal or squat plate which opens into each chamber
alternately; a floor grate to allow drainage of liquid into a drainage
tray below; a drainage tray with a 50 mm outlet approximately 25 mm above
the base of the tray that allows a standing liquid level as well as access
in case of blockage; hinged doors to prevent the entry of flies;
mesh-covered vent holes and a vent pipe that extends from the top of the
chamber to approximately 1.5 m above the roof of the toilet building; and,
a toilet building is erected on the top of the two chambers with the
stairs and the door on the side opposite to the chamber doors.
Figure 42. Locally-built batch compost toilet.
The average household size on Kiritimati is approximately 7 persons,
although household sizes vary from 2 to more than 20. The variation of a
particular household size over time appears to be greater than the
variation between households. Despite this variability, estimates have
been made of the required fallow volume of composting chambers see Table
9. On the basis of these assumptions, material deposited in the toilets
should fill the composting bins in approximately six months, assuming an
800 l in volume for the composting chamber and making allowance for the
volume of starting bulking agent and air space above the pile.
TABLE 9. Estimated Generation of Material in Composting Toilets in
|Estimated Maximum Volume/average
Toilets can be constructed with stairs with hand rails, or concrete or
timber ramps to facilitate access for the elderly or the disabled if
required. It may also be possible to create a graded access to the toilet.
Ideally, houses with raised floors, which are appropriate to Kiritimati
conditions, could be designed with toilets attached to the house and
staged access incorporated into the house design. The toilet buildings
themselves should be able to accommodate the use of traditional wall
cladding and roofing, such as coconut thatch for the roof and coconut
sticks for the walls, as well as non-traditional cladding and roofing
materials such as fibro and zincalume.
It is recommended that the plumbing system providing for the drainage of
liquid from the toilets be constructed of piping with a 50 mm minimum
diameter; that a standing-liquid level of at least 25 mm be incorporated
in the design; and, that access to clear blockages be ensured. Excess
liquid is drained from the toilet into an evapotranspiration trench to
ensure that such drainage does not reach the surface or contaminate the
groundwater. The trench should be sized to minimise the probability of
surcharging and planted with plant species that maximise
evapotranspiration from the trench. The following indigenous species are
suggested: Lepturus repens, a clumping grass; Fimbristylus
cymosa, a sedge; and, Boerhavia repens, a ground cover. Numbelle,
a hardy tree with edible leaves, can also be planted on the trench, and
has been introduced on Kiritimati as part of the nutrition program.
Raising the trench can prevent surface runoff from entering the trench and
will maximise rainfall runoff from the top of the trench. A trench that is
2 m long, 600 mm wide, and 500 mm deep will have a less than 2% chance of
surcharging, based on rainfall records for Kiritimati from 1917 to 1983,
and assuming year-round discharge to the trench; a typical system would
incorporate two such trenches, used alternately. In addition, each trench
should be fitted with a durable plastic (e.g., HDPE) liner of at least 2
mm thickness. It should be buried in a trench on a bed of coral aggregate
(which will deter crabs from burrowing underneath), and backfilled with
coral aggregate around a slotted plastic pipe and topped with 200 mm sand,
as shown in Figure 43. Food crop trees, such as papaya, banana or
breadfruit, can then be planted adjacent to the trenches to further assist
evapotranspiration. Plants or trees which provide organic matter for use
as a bulking agent could also be planted on the trenches. Fencing is
required to exclude domestic animals and children from the
evapotranspiration trench area. However, suitable fencing remains an
ongoing problem due the high cost of fencing materials (Table 10).
Figure 43. Sketch of the evapotranspiration trench.
TABLE 10. Prices of Fencing Materials.
|PVC coated fecing
||3'-06" or 7' x 15 m
||4' x 20 m
||3'-06" or 7' x 15 m
||6' x 20 m
||1-1/2" x 7'
Extent of Use
In 1982, the Government of Kiribati requested assistance from the
Australian Government to improve and protect the Kiritimati water supply
coincident with the opening of Kiritimati to immigration. A succession of
studies and design missions to the island by a number of aid agencies over
the subsequent 13 years have attempted to define the problems and propose
solutions for water supply, development and other related issues. The
Kiritimati composting toilet trial became part of the water supply project
due to the reluctance of a donor government to reticulate contaminated
water to the community, given the high incidence of enteric disease on
Kiritimati (one source of transmission of these diseases is likely to be
faecally-contaminated water), and it decided that effective sanitation be
attended to at the same time that the water supply system was installed.
The toilet sites were chosen in June 1994 by lottery as many people on the
island had no toilet and wanted one, the lottery being considered the
fairest means of site selection, and 12 toilets were installed in three
villages on Kiritimati during November 1994. Because of pressure to start
the project as soon as possible, the toilets were designed and
prefabricated in Australia and shipped to Kiritimati. Eight of the toilets
were of the Wheelibatch design shown in Figure 13 and four were Cage Batch
designs; both designs are alternating batch toilets. The Wheelibatch
toilets were installed in domestic locations on Kiritimati and the two
large Cage Batch units were installed at the primary schools in two of the
villages. One of the smaller Cage Batch units was installed at a community
clinic that was being funded by the village residents, and the other was
installed in a domestic location where the extended family members often
numbered more than twenty. Due to concerns expressed by Ministry of Line
and Phoenix Development staff that use of the prefabricated toilets would
not be sustainable due to lack of locally-available spare parts and
expertise once the aid programme was completed, three more toilets were
constructed using an owner-built design at non-government houses where the
owners were long-term residents, responsible for their own dwellings and
leased land. It was thought that the response of these residents would
more likely reflect that of the normal I-Kiribati villager. These
participants were chosen by the Mayor of the village and the village
committee of elders. Two of the toilets were given to families who had
elderly disabled men as heads of the household, primarily as a sign of
respect, and the third toilet was given by lottery to one of the many
households that had requested a toilet when the project first began. The
Mayor also offered to fund and build his own toilet to the Australian
design (he had previously installed two septic-tank flush toilets in his
home). Because of his understanding of the potential dangers to the water
quality of the lenses from septic effluent, he intended to decommission
the flush toilets when his composting toilet was built. In a similar
manner, the men of each household who were to receive the toilets would be
involved in the construction of their own toilets. Use of the
prefabricated toilets during the 10 month project; women were more
inclined to use the toilets as they offered some privacy, while teenaged
boys reported that they were embarrassed to be seen entering the toilets,
and the men preferred to use the bush or the beach. Toward the end of the
trial, some families reported that everyone was using the toilet including
the men. The gardening programme resulted in a significant increase in the
participants= interest in the composting toilets.
Use of locally-built toilets was much more consistent from the outset.
This may have been due to the more integrated design and because they had
been 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 had 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=
houses nearby, which would not have provided very encouraging example to
the children. The teachers became more interested in the composting toilet
through the gardening program, and it is anticipated that, when a greater
number of people have composting toilets at home, the children will feel
less conspicuous using the toilets at school.
Operation and Maintenance
To maintain the composting process, it is preferable that a small
handful of a bulking agent, such as dried leaves or coconut fibres, 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 develop an unpleasant odour. The
smell usually disappears after a quantity of leaves is deposited in the
toilet. As many housewives on Kiritimati sweep up leaves around the house
each day (and burn them), it is 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 fallow bin. 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 these can be dropped
into the toilet as additional bulking agent. In Kiribati, women are
responsible for sanitation in the home, and were able to complete all the
above chores without any apparent difficulty. Most women reported that it
was easier than looking after a water based-toilet. 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 poultry
will dig up the compost and scatter it around.
For the elderly or disabled who could not climb the stairs to the
toilet, a relative collects their excrement in a basket lined with leaves
and deposits the contents in the toilet. It is common practice to provide
a pan to those confined to the house, so emptying the material into the
composting toilet is not too much of an adjustment. Disabled persons who
were more agile were able to climb the stairs with assistance.
If the toilet happens become blocked, the unit can be cleared with a
stick inserted through the access point in the outlet pipe. The drainage
connections are standard polypipe hose fittings and unlikely to need
replacing as they remain connected, except for the odd occasion when the
drain needs to be unblocked. Building repairs to the frame or concrete
bins could be made with locally-available materials. If the false floor in
the bins is made of treated pine, the timber may slowly rot and require to
be replaced every six or seven years. This is a simple carpentry task. The
pedestal used in the trial was made of fibreglass and the vent pipe was
PVC, although other materials could be used or substituted during
subsequent repairs. Little else requires maintenance in this alternating
batch composting toilet design.
Level of Involvement
The introduction of composting toilets requires considerable input from
local personnel skilled in health education and community consultation
probably, probably over a 2 to 3 year period. A curriculum development
officer to work in the schools with teachers and students on water quality
and sanitation issues would also be useful. 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 water-borne 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 cooperation of the women in
the community, and sensitive issues are more effectively discussed between
persons of the same gender. Likewise, initiating a gardening programme
should be undertaken by a person having both experience with the hygienic
use of human excreta in small-plot gardening in physically antagonistic
circumstances, and awareness of local cultural considerations.
An informational programme was undertaken as part of this project to
inform the community about composting toilets. As each culture has
different attitudes about sanitation, and each community has different
requirements and limitations, ongoing consultation with the residents was
a critical aspect of implementation. The development of the informational
programme was developed with the assistance of I-Kiribati staff.
The informational programme developed included a documentary/educational
video (made in cooperation with two committed women on a shoe-string
budget), posters, and T-shirts. A song about the toilets, and mimed dance,
were composed with the input of the school teachers and the Chief of
Police, and most of the children could sing it after a couple of lessons.
There were regular discussions with all the trial participants on a
one-to-one, and on a group, basis. One of the most effective strategies
for sustained community involvement was the gardening programme that was
undertaken at each trial site by the householders or persons responsible
for the toilets. This involved planting fruit trees and the establishment
of a modest vegetable and flower garden if the householder expressed
interest. This joint effort served to create relationships that helped to
bridge the language and culture gap, create more enthusiasm for the
composting toilet, and reinforced the sanitation project , the English
meaning of which translates as "Working together for healthy
families, clean environment, fertile gardens and pure water". The
sanitation-garden programme was linked to a community-wide gardening
competition which was being conducted as part of a nutrition programme by
the Health Department.
The approximate unit cost of the locally-built composting toilets on
Kiritimati, including the toilet building, was between $1 500 and $2 000,
including all materials, I-Kiribati labour, and the liquid
drainage trench construction. A breakdown of these costs is shown in Table
Effectiveness of the Technology
The composting toilet system will be sustainable if the end-product can
be disposed of by the users within the house site. For this reason, the
compost must be free of odours and disease-causing organisms, and have a
not unpleasant appearance. Six of the toilets included in this project
were ready to be emptied of compost during September 1995. 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.
TABLE 11. Approximate Unit Costs of Composting Toilets, Buildings
and Liquid Drainage Trenches.
|Trenches and fittings
Samples of compost from the bins were inspected for the presence of Ascaris
lumbricoides (round worm), Trichuris trichiura (whip worm),
Ancylostoma duodenale, Nector americanus (hook worm), and
intestinal protozoan cysts. Bacterial tests of the compost were also
undertaken. Samples of pig faeces from an enclosed pen, liquid from a
drainage trench, and a fresh stool from a child from one of the trial
households were included in the tests as baseline data on enteric
pathogens. Trichuris trichiura (whip worm) eggs were detected in
all the compost samples inspected (Table 12), which accords with
information received from health workers who reported that whip worm was
the single most common worm infection on the island. However, composting
for at least six months appeared to be sufficient to destroy the Trichuris
eggs, as the eggs in compost showed signs of degradation. In addition to
the Trichuris eggs, the fresh faeces contained a large number of
Giardia lamblia cysts, which was also confirmed as prevalent by
the health workers. However, there was no evidence of Giardia
cysts in the compost. Subsequent laboratory tests indicated a total
absence of faecal coliform, faecal streptococci, shigella, and salmonella
bacteria in the compost samples. A number of pH tests were also performed
in the laboratory on the compost using a Gallenham single-probe pH stick
(Table 13) and indicate a range that could be expected with mature, stable
TABLE 12. Results of Pathogen Testing of Compost Samples: September
||Age of sample (months)
||Trichuris trichiura (# eggs observed)
(# eggs observed)
||present (6) degraded
||present (16) degrated
|12 trench liquid
a Test not performed, assumed to be numerous.
The advantages of installing a locally-designed composting toilet
include increased local participation in, and ownership of, the project;
increased familiarity with the concept and principles of composting
toilets through owner-building; increased likelihood of sustainable
maintenance due to the use of locally-available materials; immediacy of
construction; groundwater quality protection; reduced water usage compared
to water-borne systems; and, production of compost for gardening.
TABLE 13. Results of pH Tests on Compost Samples.
Disadvantages of this technology include access problems for the elderly
and disabled; creation of potential health hazards if the compost is
removed too early; proliferation of insects if the toilet lid is not kept
down; and, cost (the units could be too expensive for island people to
Introduction of new sanitation technology in any culture is a complex
and sensitive process as it affects peoples' lives in the most intimate
manner. In Australia, on the occasions when composting toilets have
failed, there was a lack of an information component in their
implementation, or inadequate pre-sales consultation and after-sales
support. In Kiribati, taboos related to sorcery were a concern as were
certain taboos relating to menstruating women using the toilets, although
these issues did not seem to be a problem within the family. At the
outset, there was a definite aversion to the prospect of using the
end-product as compost or any thing else that might result in contact with
the waste. However, when the piles in the toilets did produce compost,
there was relief and a marked increase in interest in the toilets.
Neighbours who had previously been disinterested or even hostile to the
project requested a composting toilet because they wanted to be able to
use the compost as a soil improvement in their gardens. As previously
noted, people were also concerned about using a toilet which was elevated
above and climbing the stairs to use the toilet. To conform to a variety
of local customs, the toilets were designed with a low pedestal which
allowed sitting in a semi-squatting position, and strong enough to support
squatting on the seat if desired.
In contrast to the composting toilet project, the installation of
septic-tank toilet systems on Kiritimati has occurred over many years,
and, now, is often considered an indication of status to have a flush
toilet in the house. As with the composting toilets, the I-Kiribati
initially found these toilets unacceptable, but, over a period of 40 years
and with the persistent efforts of community heath educators, the flush
toilets have been increasingly accepted. However, recent evidence would
suggest that water-borne sanitation systems are contributing to the high
incidence of enteric disease on the island. Because septic systems do
little to reduce pathogens, BOD, or nutrients in the effluent (Berg et
al., 1976), and discharge directly to the groundwater, parasitic
reinfection and disease transmission occurs, in part, through contaminated
drinking water (Table 14). Dye tracer studies showed that effluent from a
decommissioned septic tank, which was continuing to receive grey water,
appeared in a drinking supply well, 2.5 m from the tank within five weeks.
Given the extended survival rate of certain pathogens in water, especially
viruses and worm eggs, this result suggests that effluent from septic
tanks could also contaminate wells at some distance from the toilet. These
findings, however, no doubt, contributed to the initial scepticism
surrounding the proposed introduction of the composting toilets, and
created some initial difficulties in community acceptance of these systems
as a means to reduce the incidence of water-borne diseases.
TABLE 14. Results of Pathogen Indicator Tests of Water Samples.
||Result (faecal coliform/100 ml)a
||Main Camp - hotel tap water
||Main Camp - hotel tap water
||Heavy rain just before 7/11/94
||Banana Gallery - near Banana
||house well 150 m from septic
||house well m from septic
||Banana Gallery - water for Ronton
||house well 150m from septic
aWHO drinking water guidelines suggest that E. coli or
thermo-tolerant coliform organisms must not be present in 100 ml samples
of water intended for drinking.
An appraisal of the composting toilet programme, conducted in September
1995, indicated that, of the 316 households participating, 258 households
liked the composting toilet. On this basis, it was decided to extend the
programme to include some 200 to 300 composting toilets, with the
intention of eventually providing composting toilets throughout the
island. The project was conducted almost entirely by the two Health
Department staff members.
Future Development of the Technology
Thorough research and development of composting toilets for various
applications in both the developed and developing world is a relatively
recent phenomena. This study has shown the technology to be a simple,
sustainable sewage treatment option, well-suited to the needs of the
Kiritimati community. However, further research is required, over a
reasonable time frame, to set reliable guidelines for the handling of
toilet compost, as appropriate guidelines have not yet been established by
regulatory and health authorities for the handling of toilet compost. It
is necessary also to identify other factors that may affect pathogen
kills, such as the pH and moisture content of the compost, and develop the
necessary modifications of this technology. It is important that
microbiological and parasitological data be collected and analysed to
fully assess the utility of this technology in the longer term.
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