Manual for




The SOIL FACTORY 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:

A person living in a city 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 SOIL FACTORY consists of three main modules: 1) The top module, through which the system is ventilated and supplied with raw material and bedding. It 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 putting approximately 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 move to the 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 approximately 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 the product 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 for plants.

Biological processes:

Shortly after adding raw material, moulds and fungi appear on the surface and pre-process 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 depends 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 oust the pathogens.
The composting process is finished when the raw material has been processed into worm castings and the microbial activity has stagnated

SOIL FACTORY. A container for the bedding is mounted inside the top module. The bedding, which is added together with the raw material, contributes by optimising the C/N relationship.


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, whereupon 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 full-grown worms weigh approx 0.5 grams and consume approximately half their weight of material each day The average lifespan of the worms in a functioning vermicomposting system is 3-4 years.

Composting parameters:

Vermicomposting is an aerobic combustion process which is dependent on constant access to oxygen. A lack of oxygen may result in anaerobic processes, which produce inconvenient smells. The worms make tunnels in the material providing oxygen supply and allowing 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. This is to protect the worms from UV-radiation, in which they can not survive more than a few minutes
The worms thrive and breed optimally in a temperature between 15-25 degrees Celsius. They can survive temperatures between 0-40 degrees. The proportion of worms/bacteria is decisive to the temperature, and a large bacterial population may cause temperatures lethal to worms. This is normally not a problem, as worms dig through dense areas and create ventilation ducts in the material, whereby the temperature is reduced. Good living conditions for worms will normally keep bacterial populations down
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 must not dry out. The water contained in normal kitchen waste, together with some dry bedding, ought to ensure 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.

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 ground before it is put into the SOIL FACTORY, as this eases the transformation process
C/N proportion
The Carbon/Nitrogen 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 nitrogen 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 of C/N 15:1 and therefore one should add material containing carbon.

The bedding, which is added together with the raw material, contributes by optimising 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 mould, 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.


Common problems in indoor composting are fruit flies and inconvenient smells. Both problems result from an unbalanced process: erroneous humidity control, lack of bedding, the wrong bedding, or an overload of raw material which may cause anaerobic processes to take place


Installation of the system is easy and requires no use of tools


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. 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 comminuting 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, with 36 pc holes Ø 18 mm
2 pc stainless acid-resistant steel fittings for mounting of top module
Fly trap: polypropylene tank, 3 liters with hole Ø 2.4 mm, beer or wine
Bedding container: polypropylene tank, 3 liters, sawdust
Fly net
Black plastic sheet for covering.

SOIL FACTORY, Switzerland 2002

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