Worm Compost and Worm Composting

Worm Compost and Worm Composting

Worm composting is a very simple process, it takes up little space and it produces a quality end product.

Worm Compost and Worm Composting Making worm compost is rather like keeping your own herd of animals to produce manure, but on an easily manageable scale! Compost worms are kept in a container and fed on kitchen waste and other compostable material. They convert this to worm manure, usually known as worm compost.

The benefits of worm composting

The benefits of worm composting are that it requires little space, time or effort, it is ideal for recycling kitchen waste, it is suitable even for patio gardens and balconies and it does not give off any unpleasant smells. It also produces a high-quality compost.

The worm’s digestive system grinds and mixes food, concentrating plant nutrients and converting them into an available form. The worm casts produced (which make up the bulk of the compost) are also rich in humus and coated in a stabilizing gel, so they benefit the soil structure.

The effect of the worm compost on plants is thought to be due to the formation of plant growth hormones during the digestion process of the worm.

Garden or worm compost?

A worm compost system differs from a conventional compost system in that it works best with a regular supply of small quantities of material. A worm compost system cannot cope with any large quantities of material at one time.

Depending on your circumstances, you may rely on worm composting entirely for your garden or you may use a compost heap for the bulk of the material, with a worm system to supplement this and to cope with kitchen waste, especially during winter when it is particularly difficult to compost this waste in any other way.

Making worm compost

To set up a worm composting system you will need worms of the correct type, some bedding material, a supply of food and a container to keep everything in.

The worms

The worms used are known as “compost”, “muck”, “tiger” or “brandling” worms. Their official name is Eisenia fetida. They look similar to earthworms found in the soil but are darker red in colour, with a characteristic yellow banding. They live naturally in decaying organic matter such as compost and manure heaps rather than in the soil.

Sources of supply

The cheapest source of compost worms is a maturing compost heap, a pile of well-rotted manure or a working worm bin. The worms are easy to pick out by hand. If you look carefully, you may also find worm cocoons, tiny yellow lemon-shaped structures containing worm eggs. Collect these to add to your bin.

Compost worms can also be purchased by mail order, or bought in small tubs from fishing tackle shops. However, this latter source is more expensive.

Aim to start a worm compost bin with a minimum of 100 worms. The more there are at the outset, the quicker the system will get going and the less likely it is to fail. One of the most common causes of failure at the start is giving the worms more food than they are capable of processing.

Providing the right conditions


A worm’s skin must be moist for it to breathe, so the contents of a worm-composting container should be kept damp enough for the worms to thrive.


The container must be rainproof and well drained so that the contents do not become waterlogged and hence airless.


Worms are most productive at 18—25°C (64—77°F) and will continue to be active at 10—29°C (50—84°F). They will survive lower temperatures, but to keep the system active all year round the container should be insulated and/or kept in a warm place in winter. In summer it should not be allowed to get too hot.

Correct pH

A pH of around 7 is ideal, although the worms will tolerate a pH of 5—9. Ground limestone can be used to raise the pH if the compost is too acid.

Worms will always move away from the light, so a worm-composting container should keep its contents dark.

Bedding material

When starting a worm compost bin you will need to provide bedding material for the worms to live in until they have produced some compost. Suitable materials include well-rotted compost, manure or leafmould. These can be mixed with equal parts of shredded paper or cardboard. A couple of handfuls of sand or ground limestone can be added to help the worms’ digestion, though this is not essential. The bedding should be moist but not dripping wet.

Food for the worms

Compost worms can eat almost anything that will decompose. A varied diet is preferable, including items such as: annual weeds; vegetable peelings; tea leaves; coffee grounds; food scraps; crushed eggshells; citrus peel (not in large quantities); shredded newspaper; and half-rotted compost.

Materials that must be avoided are weeds with seeds, perennial weeds and diseased material. A worm compost system will not kill these.

Siting the container

A worm bin should be kept where it will not overheat in the sun nor get too cold in the winter. A frost-free shed or a sheltered, not too sunny spot in the garden is ideal. The bin may need to be insulated or moved into a warmer place in the winter.

If the bin is to be used primarily for kitchen waste, a position near the kitchen is sensible and the most convenient. As long as the worm bin is working well, there will be no smell.


Worm compost can be made in a variety of containers, home-made or purchased. The container should be seen as a home rather than a cage for the worms. If the conditions are right they will not try to escape.

To make a good worm bin, a container should keep moisture in and rain out; allow some air circulation; have good drainage; exclude light, flies and vermin; be insulated; and be mobile.

Worms like to feed near the surface. A container with a relatively large surface area will be able to deal with more food than one that is tall and thin.

Making worm compost

The best time to start a worm compost bin is in late spring and summer, when the warm temperatures activate the worms. A range of plastic, wooden and compressed paper bins are available, but it is more economical to make a worm bin by adapting a standard domestic plastic dustbin. Alternatively, recycle a wooden box or make one. Never use wood preservatives, as they may kill the worms. As there is no need for the- container to have a base, unless you want to move it, you can use a conventional compost bin.

Using a plastic dustbin

You will need:

  • A lidded plastic dustbin which has as wide a surface area as possible
  • Coarse sand or gravel to fill the bin to a depth of approximately 7.5-10cm (3-4in)
  • Boards, a circle of wood or some tough polythene to separate the compost and gravel
  • Bedding material to make a layer about 7.5cm (3in) deep in the bin
  • At least 100 worms
  • One whole newspaper, soaked in water
  • Approximately 1-2 litres (1-¾ — 2-1/2pt) chopped kitchen waste.

Feeding the worms

How much and how often you can feed a worm bin depends on how many worms there are, the temperature (and consequently how active they are) and the surface area of the worm bin. It is something that is learnt by experience. The most valuable hint is to err on the side of caution until you get to know the capacity of your worm bin. The worms are much more likely to be killed by overfeeding than by starvation.

A worm compost system can only process small quantities at any one time. The worms are unable to chew up kitchen scraps and feed instead on the soft bits that are beginning to decay. This is why a good working worm bin should never smell — because the worms continually eat the rotting material. If they are given more food than they can cope with, the material tends to putrefy, making the compost acid and smelly and the conditions unsuitable for the worms to function in. If large quantities are added, there is also the risk that it might heat up.

Collect a litre or so of suitable food; smaller quantities can of course be used. Chop up tough items such as raw potatoes, cabbage leaves, carrots and citrus peel. If you collect vegetable waste in a plastic box or other similar container, put a newspaper in the bottom of the collection container to soak up excess moisture (this can also be added to the worm bin) and empty it regularly.

Put the food on the surface of the material in the container in a layer no more than 5cm (2in) deep. Do not cover the whole surface; leave an area for the worms to move to in case they do not like what you have given them. Cover the food with moist newspaper.

Alternatively, bury the food in small batches around the bin. Some people prefer this method as it puts the food out of sight, but it is then more difficult to gauge the rate of feeding.

When the previous addition of food has been well colonized by the worms, a new batch can be added, preferably in a different spot. Never add more food until you are sure that the worms will be able to cope with it.

An established working bin should be able to process the food waste from an average family of four. If necessary, start a second bin.

There is no need to worry about getting a “worm sitter” to look after your worms while you are on holiday. Feed them before you go in the usual way and they will survive quite happily until you return.

Problem solving

Check for the following common problems:

• Worms congregating around the top of the bin

If there are only a few worms; do not worry. If there are large numbers, this indicates that the conditions within the bin are wrong.

• Worm bin infested with tiny flies

These are likely to be fruit flies, introduced to the worm bin on the food scraps. Try to prevent the problem occurring by keeping the collecting container, the food in the bin and the bin itself covered. Check that conditions in the bin are suitable. Hoover up flies.

• White thread-like worms in the bin

These are enchytraid worms, not young compost worms. Generally they do no harm and should be ignored, although a large numbers can indicate that conditions are too wet or acid.

• Worm bin smells unpleasant

This indicates that the worms are not processing the food sufficiently quickly. Reduce feeding and check the pH, moisture content and temperature.

• No worms to be found in the bin

The worms have either left (if this is possible) or died because conditions are not suitable. Check feeding, drainage and pH. Never use wood preservatives or insecticides on a worm bin.

• Contents of the bin too wet

Check drainage holes are not blocked. Mix in shredded newspaper to soak up excess moisture. Avoid adding liquid when feeding worms.

If, after checking for all these symptoms, the worm compost is still not right, it may be that the contents of the bin is too acid. To remedy this, fork a handful of ground limestone or dolomite into the compost and reduce the quantity of citrus peel given. If a problem seems intractable, it may be worth emptying the worm bin and starting afresh.

When is it ready?

Over the months the worm bin will gradually fill up with rich compost, although the top layer will always consist of semi-rotted material as you continue to add food.

The speed at which the compost builds up depends very much on how much food is added, the number of worms present and the time of year. It is possible to make several full containers in a year, or you may find that you only make one annual batch which does not even fill the bin.

Extracting the compost

Compost can be removed from the bin whenever it is available by simply digging some out with a trowel. This is fine if you only want a small quantity at once.

However, if you want to remove all the finished compost from the bin it is best to do this in spring or summer so that you can get the bin going again quickly. If possible, keep the container full over the winter months because this gives the worms added insulation against the cold.

To empty the whole container, first remove the top layer, which will consist of food, half-rotted material and worms. Set this aside for starting the bin again.

Empty out the remaining contents, which should be finished compost, mixed with some worms. If you are not using the compost straight away, it can be stored in bags provided you spread it out to dry before bagging up.

There may still be a lot of worms mixed in with the finished compost. There is no need to remove them unless you want to use them to set up another worm compost bin or the compost is to be used in pots and other containers, where their activities can disrupt the growing plants.

Extracting the worms

To separate the worms and compost, make use of the fact that worms will move away from heat, dryness and light. To do this, spread the compost out in a thin layer on a sheet of plastic or a similar material in a sunny spot. Place one or more folded-up wet newspapers on the compost to act as refuges for the worms. As the compost dries out in the sun, the worms will move into the cool, moist compost under the newspaper.

Alternatively, heap the compost up into small “molehills”. Leave these for an hour or so and then scrape away the outer layer of each molehill, which should be worm-free. Repeat the process until the molehills are mostly worms.

Liquid feed

Some worm bins have a sump fitted with a tap to allow any liquid that has collected to be drained off and used as a liquid feed. The composition of this liquid will obviously vary; use it diluted at a rate of at least 1 part liquid in 10 of water.

Wooden and other non-plastic bins are unlikely to produce excess liquid. The goodness stays in the compost.

Making worm compost

1. Drill holes 2.5cm (1 in) and 7.5cm (3in) up from the base and around the top. Fill with 10cm (4in) of coarse gravel or stones.

2. Cover the gravel with boards or a perforated plastic sheet to separate gravel and compost.

3. Add 7.5cm (3in) or so of bedding material, along with the worms and some food. Cover with a wet newspaper.

4. Spread the finished compost out in the sun and the worms will collect under the wet newspapers.

29. January 2011 by Dave Pinkney
Categories: Manures and Fertilisers, Organic Gardening, Soil Cultivation | Tags: , | Comments Off on Worm Compost and Worm Composting


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