Choosing a wormery
There is a wide range of wormeries available, usually made from recycled plastic, supplied complete with bedding materials, instructions, and worms. They are generally either dustbin-like or modular stacking systems, varying in size from small bins designed to fit in a kitchen cupboard up to large wheelie bins, and domestic systems generally cost from about £40 up to £200 or more.
Which type is most suitable for you depends on the amount of waste you want to dispose of, how much time and effort you are prepared to put into taking care of it, and where you plan to keep the unit. The easiest type to use are the stacking systems, which have several layers of trays for the worms to move up through, leaving compost ready for use in the lower trays.
For examples, see the selection of wormeries at the turning2green shop.
Wooden worm bins are available from The Recycle Works .
It’s also very easy to construct your own worm bin.
Not all species of earthworm are suitable as composting worms. The long plump pink earthworm most commonly found in the garden is the lob worm, which is a deep burrower and will not survive in a wormery. The worms generally used for vermicompostin are the European Nightcrawler or dendra, and the Red Tiger Worm or brandling/manure worm. Both live near the surface and feed on decaying organic matter. Dendras are generally found living in damp leafy woodland, in compost heaps, and in rich soils. Brandlings are found in manure heaps and compost.
Worms don’t have eyes but they are very sensitive to bright light and will try to hide as soon as exposed to light. They have no lungs but instead take in oxygen through their skin straight into their bloodstream. The skin must stay wet in order for the oxygen to pass through it, but they can drown if they are in too much water.
Worms can eat half their own weight in food each day. They have very small mouths and no teeth, so will only take very small particles of food which has already been softened by micro-organisms. This is mixed with grinding material such as sand, or fine grit, then contractions from the muscles in the gizzard grind the food into smaller pieces. After passing through the gut of the earthworm, the recycled organic wastes are excreted as ‘worm casts’ which look like fine soil. Secretions from the intestines make the nutrients in ‘worm casts’ more concentrated and more easily available to plants than those in traditional garden compost.
Worms mature in about three to six weeks after hatching and can then breed every three to four days. The cocoons are smaller than a grain of rice, yellow, and look like tiny lemons . Each contains between one and six worms and will take around 3 weeks to develop. The colour changes from pale yellow to mid brown as the worms grow inside. The baby worms are white. Cocoons are very resilient and, if the conditions are not right for hatching, can remain dormant for years ready to hatch when the conditions improve.
Siting the wormery
A wormery can be sited in a garage or shed, and some are even designed to fit into a kitchen cupboard. If the wormery is to be outside, it needs to be easily accessible from the house and in a position where it will be shaded in the summer and out of strong winds. In the winter it’s best kept in a shed, utility room or garage, as worm activity ceases below 10 degrees centigrade. The worms can be kept outside all year but the container will need to be insulated by wrapping with old carpet or bubble wrap and tucking some straw inside.
Starting up the wormery
Put a damp sheet of newspaper into the bottom of the worm bin, and cover this with shredded newspaper which has been slightly dampened with water. Add a pile of worm bedding, well rotted compost, or some leaf mould, and mix in a little garden soil. Place the worms on the bedding and leave the lid open for a few minutes until the worms have burrowed down out of sight. Put in a few handfuls of finely chopped kitchen waste, then replace the lid.
The worms now need some time to settle, and probably will not need any more food for about a week. In the early stages they should be be left undisturbed to establish themselves in the bedding layer, then once they begin activity in the waste layer you can start adding more food.
It takes a while for the worm colony to establish, and so for the first week or so the worms are likely to try to leave, especially at night. Unfortunately it’s impossible to prevent this, but some garden soil mixed in with the initial bedding does seem to help them settle. Keep the lid tightly on. A piece of damp cardboard on the lid and another below the bin act as a refuge for escaping worms so they are easily caught and returned to the bin. Or you can put the whole wormery in a bin liner and seal the top overnight so any worms which escape are trapped and can be returned to the bin the next morning. Once the worms are settled they will stay in the bin.
Feeding the worms
It’s best to feed the worms sparingly at first, and don’t add any more until the previous food has gone. Worms can eat up to half their own body weight every day so as a guide, if you start off with 1 kilo of mature worms they will need up to 500g of food waste per day. The population will gradually increase and you can feed them more.
The rate of food consumption depends on the time of year, the temperature, and and how long your wormery has been running, but you will soon become familiar with the workings of your own system. When it gets colder in the winter the worms will slow down and will not be able to digest as much food waste, so you will need to cut back on the amount of food waste you feed them. When working normally the wormery should smell earthy – bad smells generally arise when the bin is too wet or when excess food begins to rot and the compost becomes anaerobic. Never overfeed, and once a week or so carefully fork through the top of the compost and food to allow air to penetrate to keep the worms happy. Remember to drain off any liquid regularly – this can be diluted 1 to 10 with water and used as plant food.
If you are using a stacking tray system, you will need to encourage the worms to keep moving upwards by adding some of the compost from the bottom layer each time you start a new tray at the top. This introduces bacteria needed for the composting process, and also gives the worms some bedding to move into. Allow the worms time to finish composting the food in the lower tray. A tray will probably take one or two months to fill, then about four or five months to finish composting, depending on the time of year.
The worms will eat most normal kitchen waste such as vegetable and fruit peelings, tea bags and coffee grounds, left-over cooked food, crushed egg shells and stale bread. Also most other organic wastes such as pet bedding and the dust from the vacuum cleaner bag, shredded paper and pre-soaked cardboard. The more variety the better. The ideal balanced diet is composed of about half kitchen waste and the remainder a mix of paper, cardboard and leaves. They are not keen on tough, woody waste, spicy foods, fat, raw onions, or very acid foods such as citrus fruits. Food scraps are broken down more quickly if they are chopped up before adding to the bin.
Never add anything with traces of insecticides or pesticides, poisonous plants, salt, soaps or cosmetics, paints solvents or non-biodegradables.
Pet bedding from rabbits, hamsters, guinea pigs, gerbils, mice etc – sawdust, straw, hay and paper bedding – can safely be added to the wormery
Dog and cat poo can occasionally be put into a wormery but if you need to compost this type of waste on a regular basis it will work much better in a separate wormery used solely for pet waste mixed with shredded paper. Dog and cat waste can contain dangerous pathogens, so never use the vermicompost where children play or where you grow food crops.
Chicken manure – before adding to a wormery, chicken manure needs to be well aged or pre-composted as it is very high in nitrogen and ammonia and will get very hot when composting which could kill your worms.
Horse manure – the worms love horse manure, but again it needs to be pre-composted to take the heat out before putting in a wormery.
Garden waste/grass mowings – a little is good, but too much is likely to heat up as it decomposes in the bin and will kill the worms.
Organic biodegradable nappies – worms can compost these nappies, but the volume produced by just one baby is too much for a normal domestic wormery. Ecobaby have done some research on this and have come up with experimental plans for a large DIY Vermicomposter for Eco Nappies.
Emptying the bin
When the system is full it’s time to harvest the compost, and there are various ways to do this depending on what type of bin you are using.
The stacking tray types are designed to be harvested as you go along, taking the finished compost from the tray at the bottom each time and replacing the emptied tray at the top of the stack.
In a shallow tray system you can move the worms and finished compost over to one side, then add new bedding material and food on the other side. In a few days most of the worms will have moved across the tray to the new food supply, and the finished compost can be removed from the other side of the tray.
Dustbin or box systems can be emptied out completely and everything used in the garden, including the worms, then started again from scratch. Or, if you want to separate out and keep the worms, they should be fed plenty of their favourite food a few days before harvesting. This will bring most of them to the top of the bin. To harvest, quickly remove the layer of uneaten food waste together with the worms, and place to one side in a bucket.
Now either fork out compost from the bin into a garden sieve and carefully sift out the coarse material and the remaining worms. Collect these up to return to the bin. Leave some compost undisturbed in the bottom of the bin as this will contain most of the worm eggs. The sieved compost is ready for use in the garden.
Or tip out the remaining contents of the bin onto a plastic sheet. Make it into several cone-shaped piles, then leave these to stand for about half an hour. The worms will gather together in the centre of the piles. Carefully collect up the compost from all around the sides and the top until you reach the worms, then remake the piles and repeat the process. Keep doing this until just the worms and a little compost remain. They can then be returned to the worm bin with the compost as starter bedding. The rest of the compost is ready for use. It can be stored before use in a bin to keep it dry.
Once the bedding and worms have been returned to the bin, replace the layer of uneaten food waste and the rest of the worms, leave the bin for a few days to settle, then simply start adding food back into the wormery as before.
Using the compost
Worm compost is very rich and can be used as a mulch on soil, mixed into the soil when planting new plants, used for topping up the compost in container-grown plants or mixed into potting compost.
The nutrient rich liquid produced by the wormery makes good plant food when diluted with 10 parts of water. The amount produced depends entirely on the type of foods being composted, and it may take months for any liquid to be produced.