Download Observations on the breakdown of faeces in bags and buckets held

Observations on the breakdown of faeces in bags
and buckets held within UD toilet vaults
Peter Morgan and Annie Kanyemba
June 2008
The materials observed were collected in a single vault
urine diverting toilet where the urine was separated off to
a plastic container and the faeces dropped directly into a
sack contained within a 20 litre bucket held within the
vault. In this technique the sacks are taken out and
replaced with new empty sacks.
Parts of the toilet
The sack fills with a combination of faeces, soil and ash and
toilet paper. Leaves or soil are added to the base of the sack
before it fills. As the sack fills material lower down starts to
convert into compost. When the sack is full the uppermost
layers are raw material. These raw materials are covered with
more soil and the sack closed off and stored in a safe place
(which may be the vault itself).
Over a period of months the soil organisms eat into the
excreta and convert it into a soil like material. The
conversion is faster if the soil is well dispersed with
excreta. It is slower if larger amounts of excreta are not
exposed to soil. Below a bag of material is emptied into
a wheel barrow for observation.
Two sacks were observed closely on 14th August
2008.
The first sack had been closed off on 31st March 2008 after adding some
soil, leaves and some red worms. (about 20 weeks)
The second sack had been closed off on 20th May 2008 after adding some
soil, leaves and earthworms. (about 13 weeks)
For smaller “nobules”, the conversion was almost complete after about
4.5 months, but not complete after 3.75 months)
However for larger pockets of excreta the conversion had not been completed in
either sack. See next slide.
Observations on the breakdown of faeces in bags held for 4.5
months (31st March to 14th August)
Note the pockets of raw material had been reduced considerably and the
survival of healthy “red worms” in the material. Small red worms were
placed in the sack on closure together with soil and some leaves.
Observations on the breakdown of faeces in bags held for
2.75 months (20th May to 14th August)
Note the larger pockets of raw material had not been reduced so much
and still contained much raw material. Common earthworms added to mix
on sack closure appeared to have died out.
Activity of red worms in shallow pit
composting systems.
Initial trials: Red worms being added to composting pit
of Fossa alterna
Activity of red worms in shallow pit
composting systems.
Initial trials: Red worms being added to “filling pit” of
Fossa alterna
Conclusions
1. The addition of soil (and ash) to excreta promotes
conversion of excreta into “compost.”
2. Conversion is faster as the ratio of soil to excreta
increases (the more soil the better!)
3. Conversion is faster as the area of interface (ie proximity
of soil to excreta) increased. (ie a better mix helps)
4. Red worms appear to thrive in or close to raw excreta
5. Red worms are know to be good converters of waste
products into good compost
6. Earthworms appear to be less tolerant of such conditions.
7. It is possible that red worms could assist in the conversion
of excreta to compost in composting material being
processed in urine diverting systems and also in shallow
pit compost toilets (Arborloo and Fossa alterna)
Overall conclusions
The addition of soil and ash helps the conversion of raw
excreta into a more easily managed and valuable compost. A
period of at least 6 months is required for the conversion in
sacks in urine diverting toilets and in shallow pits for up to
one year.
Red worms appear to assist the conversion and their role
may become more important in the future for shallow pit and
urine diverting technology options.
A biological process in the composting process does require
the presence of beneficial soil organisms (bacteria etc) and
some moisture in the system.
Care must be taken in areas where worm infections are
common (eg Ascaris). Where there is doubt, the material
must be buried underground (in tree pits or garden trenches)
or stored in sacks.