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• Urine collection provides a great extent of recirculation of nutrients,
and the process is technologically uncomplicated. The greatest
problem is blocking and cleaning of valves and small tubes/pipes in the
urine separating toilets and pipe systems for urine. The problem can
be limited by regular caustic scrubbing, but could also be solved in
another way, so that the system provides a level of comfort similar to
that of traditional toilets.
• Composting toilets for faeces, if possible with addition of organic
kitchen waste, have been dropped in urban areas, due to great
difficulties in obtaining complete composting, difficulties in obtaining
a texture of the end product, which is easy to handle, high energy
consumption and different nuisances from smell and flies.
• The best application of waste products seems to be biogasification of
kitchen wastes, faeces and urine, preferably together with other
suitable materials. This uses the full recirculation potential for
nutrients, and at the same time energy is extracted from the organic
material. However, problems often arise from poor sorting of kitchen
waste and economy of operation. If large volumes of urine are applied,
the process can be hampered by the considerable extent of ammonium
in the urine.
• Most systems imply more and closer contact with urine and faeces
than traditional waste handling systems. This increases the health risk.
Automation of the systems for collection, transport, treatment and
disposal can limit the risk compared to the present manual handling of
waste in systems which so far have not been tested.
• The systems described involve a certain transitional period and will for
some time pose an increased health risk. It is estimated that after the
transitional period there will still be an increased but limited health risk
in changed handling, even if a number of precautions are followed.
Example of system which can be established at a larger scale after further
development
One of the previously recommended systems is shown in figure 1. The system
is based on collection and gasification of organic kitchen waste, urine and
faeces, whereas grey water is disposed of by means of percolation or the like.
The advantage of this system is a very high degree of recirculation of nutrients
combined with utilisation of the energy in the material without loss of
nutrients. Compared to traditional systems, a large surplus of energy is
obtained, partly due to fertiliser savings, and partly due to direct production
of energy. Furthermore, the proposed collection method gives a substantial
water saving.
Experience with certain parts of the proposed solution indicates that the
following aspects should be improved: Joint collection of urine, faeces and
kitchen waste will be more safe and sturdy if kitchen waste is collected
separately and if vacuum toilets or water-free toilets are applied with
collection of urine and faeces in a separate tank. The technological
development of vacuum toilets is reasonable, but some improvement can be