What is it?
Worm composting, or ‘vermiculture’, means using small wriggly red worms to produce compost and liquid fertiliser from kitchen, garden or agricultural waste. The most common compost worm is Eisenia fetida (common names tiger worm, red worm, brandling worm or red wrigglers). They can be found in gardens living under stones, flowerpots and logs, and in large quantities in compost heaps and manure piles. They live in decaying organic material and feed on the bacteria which grow there, so they naturally migrate into piles of decaying matter such as heaps of leaves, compost or manure. If the conditions suit them (i.e. not too hot, too cold, too wet, too dry or too acidic) they breed, and soon the heap is teeming with wriggly red worms. They are different from earthworms in that they are smaller, and live on decaying matter at the surface rather than burrowing deep underground.
A wormery is a closed container where well-chopped, moist kitchen and garden waste is broken down by worms which you have introduced into the container deliberately. Wormeries are useful for making compost and dealing with organic waste in small spaces such as urban gardens and balconies. Small wormeries often consist of several perforated plastic trays which stack on top of each other, with a lid at the top to keep out light and maintain moisture, and a liquid-collecting sump and tap at the bottom. However, any light-proof container with a lid, ventilation, and a drain can be used as a wormery, so they come in other designs including some that are more like wheelie bins with a tap, or others which are a large flat box with a lid. They can be home-made or factory made. Worm compost can also be made on an agricultural scale in long brick-built worm beds, 2ft (600mm) high and 4ft (1200mm) wide.
Composting with worms in wormeries first became popular in the USA in the 1990s due to the work of Mary Applehof who wrote the best-selling book Worms Eat My Garbage, and set up a successful business selling wormeries. A few years later, in the UK, the popularity and availability of wormeries was boosted by the book Composting With Worms by George Pilkington.
What are the benefits?
Wormeries are good for dealing with cooked food waste (including small amounts of meat and fish) which you might not wish to put into a normal compost heap because doing so would encourage rats. Wormeries are usually rat-proof, unlike compost heaps. It’s much better to compost all your food waste at home, as any that goes into your black bags will usually end up in landfill, where it will break down anaerobically, producing various types of pollution including large amounts of greenhouse gases which contribute to climate change.
Even if your council has introduced a separate food waste collection scheme, if you have a garden or lots of pot plants, why give away a good source of plant food?
The main output of a wormery is nutrient-rich liquid plant food (often called worm ‘tea’) that you collect in a container as it drips out of the wormery, then dilute with water and use to feed house and garden plants. Wormeries also produce a very concentrated, high-quality compost which is useful to add to soil or mix with other compost as a potting mixture.
Worm composting is fast – worms can eat half their bodyweight each day, so organic material will break down much more quickly with worms than by conventional composting. Worms also destroy pathogens.
It can be educational and fascinating to keep a wormery, and a wormery is a good use for a shady corner of the balcony or garden where not much would grow.
What can I do?
Buy or make yourself a wormery, buy or find some redworms or tiger worms (also known as brandling worms), and start composting with worms!
Get a wormery and some worms
It is very straightforward to make a suitable wormery from old plastic boxes (or wooden ones) using basic DIY skills. You will easily find plans and youtube videos showing different methods of doing it, but in essence a wormery is just a light-proof box with a lid, some ventilation holes (preferably covered with fly-proof mesh), and provision to collect and drain off the worm liquid. Factory-made plastic wormeries are usually a set of stacking trays each about 3-4 inches (75-100mm) deep: this design can be convenient as it is space-efficient and makes removing finished compost easier, as the worms will always move into the top layers of freshest material leaving just compost in the bottom layers. Home-made wormeries are usually just a single lidded box about 2ft (600mm) deep, though a shallower box with a bigger surface area will work just as well or better.
You can find suitable red wriggly worms in large quantities in some compost bins, manure piles, and piles of decomposing leaves. Alternatively you can buy wormery worms from several UK websites, or from fishing shops where the same types of worms are sold as fishing bait.
Using the wormery
Worms prefer a mixed diet, so don’t only feed them your cooked food – give them veg peelings, outer leaves, and damp cardboard and newspaper too. When you add cooked food, bury it just under the surface to discourage flies. If space allows, add the food to a different corner of the wormery each week, and cover with damp newspaper or cardboard. Although this is an ideal approach, most wormery owners just chuck it in anywhere and close the lid! Do break up, slice or chop the food and vegetable waste which you add to the wormery – a big chunk of bread or half a cabbage will take ages for worms to break down.
There are a couple of items of food waste which shouldn’t be put into wormeries. Worms don’t like citrus skins or anything in the onion family such as onions, leeks and garlic (but very small amounts are OK). If you have a compost bin, just put your citrus and onion waste in there instead. You should also not add large amounts of fatty food such as cheese (but again, small amounts are OK).
Keep your wormery in a shady place (or shade it from the sun) and keep it frost-free in winter by moving it into a shed or making it an insulating jacket of some description.
You don’t necessarily need a special wormery to do worm-composting. The boundary between what is a wormery and what is a compost bin is often blurred. A typical plastic cone-shaped compost bin, if kept in a shady place on soil, may turn into a wormery if local composting worms find their way in and like the conditions there!
The commonest problem which affects wormeries is that they get too wet. If the outlet tap blocks, then the wormery can fill up with worm-output liquid and the worms will drown. If the tap ever stops dripping, check for a blockage (often consisting of worms, food or compost particles, or a slug or snail). You can unblock the tap by poking a length of stiff wire up it. Better still, remove the tap and fit a larger outlet pipe that won’t be so prone to blocking.
Worms sometimes try to crawl out of the wormery – this can indicate that the wormery is too wet or too dry or the ventilation holes may be blocked. Unblock the tap or ventilation holes if necessary, and add scrunched up newspaper to make the wormery drier, or sprinkle with water to make it damper, as appropriate. The contents of the wormery should be moist but not dripping wet – if you squeezed some in your gloved hand, just a few drops of liquid should come out.
When emptying compost from your wormery, if you find that there are still a lot of worms in the finished compost, you can use light to separate worms and compost. Leave a big pile of compost in the sun for a few minutes, then scrape off the top couple of inches which will now be worm-free. Repeat this process several times until you are left with a pile of worms which you can just put back into the wormery. Another method is to spread the compost thinly on a polythene sheet, with some wet newspaper placed on the compost in the centre. As the compost dries, the worms will seek shelter under the wet newspaper.
You have a duty of care to your worms. Like any animals in your care, you need to keep an eye on them – check them regularly and make sure they are fed frequently. Wormeries can go a maximum of a month between adding material, so if you are away for a long time ask someone to look after them.
It is illegal to transport food waste without a licence, even between your home and the allotment, though most people would ignore this as a silly technicality. The law does mean that you would need a licence if you plan to set up a food waste collection service to supply your growing collection of wormeries. Composting food waste on a very large or commercial scale cannot legally be done with wormeries – the regulations require you to use a hot-composting process – but the use of a wormery at home for your own food waste is of course perfectly legal.
Thanks to Fred Miller of Down To Earth for information.
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