Manual for
SOIL FACTORY
Introduction:
This system enables persons to produce their own soil. By the process of vermicomposting
the organic waste of a small household (3-4 persons) is effectively transformed,
leaving a highly fertile substance. The system is made for indoor use.
Technical background:
Every urban person produces approximately 100 kg of organic household waste
per year. By using this material in the Soil Factory or similar systems, it
can be transformed into soil. Although it is not the most effective system,
vermicomposting is a simple and cheap way of composting. The decomposition
is done partly by worms, partly by other organisms and microbial processing.
The worms´ digestive tracts perform efficient microbial and chemical
transformation, and their activities provide the mechanical work also necessary
for the composting process: mixing, draining and aeration.
System components:
The system consists of three main modules: 1) The top module, through which
the system is ventilated and supplied with raw material and bedding. The top
module also keeps out light and reduces odour inconveniences. A thermometer,
a fly trap and a container for bedding is mounted on the inside. 2) The middle
module, consisting of three tanks containing the worms, the raw material and
the resulting product. 3) The bottom module, which collects excess fluid.
The composting process is initiated by filling approx. 1000 worms and some
organic material into the upper tank of the middle module. When this tank
is full, it is exchanged with the next empty tank in the column. The three
tanks are all perforated in the bottom, to allow excess water to pass through
to the bottom module. This is done in such a way that the worms will also
be able to move upwards in the system. As the worms process the material,
they will by themselves move to top layers where there is access to fresh
raw material. When the tanks are full, they should be allowed to rest for
some time in order to complete microbial and worm processing and to allow
the worm cocoons, which are placed in the deep layers, to be hatched. After
approx. 6 months the material in the lowest tank is transformed into a black,
soft substance mostly consisting of worm castings, a large part of which is
humus. Some of the material will be products of bacterial consumption, and
there will also be occasional residues which have not been degraded. This
substance can then be mixed with sand, peat, gravel etc. for ventilation and
volume and in order to lower the concentration of nutrients. One has now produced
good nutritious soil. The drained water in the bottom module is also highly
nutritious.
Biological processes:
Shortly after adding raw material, moulds and funghi appear on the surface
and preprocess the material before bacteria and worms take over. Apart from
these, beetles, mites, flies, nematodes, snails, springtails, woodlice and
other species may be present in the composting modules. The number of species
present depend on many factors, such as the age, humidity, temperature and
composition of the material and the access to the composting modules. Anaerobic
bacteria may thrive in the material if it gets too dense and therefore is
not thoroughly ventilated. Pathogenic bacteria normally will not survive in
the compost, as the environment simply favours the growth of other bacteria,
which thereafter oust the pathogens. The composting process is finished when
the raw material has been processed into worm castings and the microbial activity
has stagnated.
Worms:
Many different types of worms can be used in composting processes. Eisenia
foetida, which is the worm used in this system, is among the soil surface
dwelling or compost preferring species. These species prefer to live at or
near the soil surface or in compost heaps, since they like to eat material
which is high in organic matter. The worms are hermaphrodites, producing both
sperm and eggs, but are dependent on each other for reproduction. They reproduce
by joining mucus from their clitella, exchanging sperm. The mucus hardens
into a cocoon where sperm and eggs are deposited, where-upon the worm backs
out of the hardening cocoon. After being released from the worm, the cocoon
closes at both ends, and 2-10 eggs are fertilized. Approximately 2-3 baby
worms are hatched after 3 weeks. After 9 weeks the new worms are fertile,
and under optimal conditions they will produce 2-3 cocoons per week for 6-12
months. The fullgrown worms weigh approx 0,5 grammes and consume approx. half
their weight of material each day. The average lifespan of the worms in a
functioning vermicompost is 3-4 years.
Composting
parameters:
Ventilation
Vermicomposting is an aerobic combustion process which is dependent on a constant
acces to oxygen. A lack of oxygen may result in anaerobic processes which
produce inconvenient smells. The worms make tunnels in the material which
provide oxygen supply and allows CO2 to escape. This is also important for
the bacterial processes. If the material gets too dense, or the tank is too
deep, these tunnels collapse. The surface of the material should be exposed
to air, but loosely covered by e.g a black plastic sheet, in order to protect
the worms from UV-radiation, in which they can not survive more than a few
minutes.
Temperature
The worms thrive and breed optimally in a temperature between 15- 25 degrees
Celsius. They can survive temperatures between 0-40 degrees. The proportion
worms/bacteria is decisive to the temperature, and a large bacterial population
may cause temperatures lethal to worms. This is normally no problem, as worms
dig through dense areas and create ventilation ducts in the material, whereby
the tem
Humidity
The vermicomposting process depends on a good humidity balance. If the material
becomes too wet, the worms may drown, but the worms need moisture in order
for the air exchange to take place through their skin. Therefore the compost
neither should dry out. The water contained in normal kitchen waste, together
with some dry bedding, normally ensures a good moisture balance. If the compost
should become too dry, some water can be added. As long as water is condensed
on the inside of the covering plastic sheet, the compost is moist enough.
Ph
The worms thrive at a neutral pH value of 6-7. If the pH gets too low, a calcareous
product could be carefully added.
Raw material
All kinds of organic waste can be added to the Soil Factory, although one
must make sure that the material is not toxic or corrosive etc. Fruit, vegetables,
coffee grounds, teabags, egg shells, bread, dairy products, paper, cardboard,
coffee filters etc., are all suitable. Fish, shellfish and meat may cause
severe odour inconveniences. Plastic and metals must be avoided, as it is
normally not degraded in the compost and may be toxic. One must also be careful
adding sauce or soup, which may disturb the humidity balance. The material
could be cut or grinded before it is put into the Soil Factory, as an increased
surface eases the transformation process.
C/N proportion
The Carbon/Nitrogene proportion is essential to the composting process. If
the amount of carbon is high in relation to the amount of nitrogen the process
slows down. If the share of nitrogene gets too high, there is a risk of ammonia
appearing in the compost. Bacteria and worms thrive optimally at a C/N proportion
of 25:1. Kitchen waste normally has the proportion C/N 15:1 and therefore
one should add material containing carbon.
Bedding
The bedding, which is added together with the raw material, contributes by
optimizing the C/N relationship. It also regulates humidity and helps ventilate
the compost by preventing it from becoming too dense. The bedding must be
rich in carbon, toxin free and fit to absorb moisture. Shredded paper, cardboard
and newspaper, leaf mold, peat moss and sawdust can be used. One must make
sure that the sawdust comes from untreated wood, as otherwise it may contain
toxic substances.
Problems:
A common problem in indoor composting is fruitflies and inconvenient smells.
Both problems result from an unbalanced process: erroneous humidity control,
lack of bedding or use of the wrong bedding, or an overload of raw material
which may cause anaerobic processes to take place.
Installation:
Installation of the system is easy and requires no use of tools.
Maintenance:
Fresh raw material should be added every week. 1000 worms consume approx 0,25
kg of raw material each day. The worms can be left alone for up to three weeks,
but in order to keep up the population they should be fed on a regular basis.
The volume of the kitchen waste is greatly reduced by the process and in a
normal household one composting tank is normally filled up after 2 months.
When all three tanks are full, the process in the lower tank is completed,
and the tank can be emptied.
Extra equipment:
A grinding mill can be attached to the top module for easy comminution of
the raw material. The system can be insulated for outdoor use.
Component list:
1000 pc composting worms (Eisenia foetida), 2 pc black PE tanks 40 x 40 x
30 cm., 3 pc black PE tanks w socket, 40 x 40 x 30 cm, w 36 pc holes Ø
18 mm., 2 pc stainless acidproof steel fittings for mounting of top module,
fly trap: polypropylene tank, 3 l w. hole Ø 2,4 mm, beer or wine, bedding
container: polypropylene tank, 3 l, sawdust, fly net, black plastic sheet
for covering.