Home Composting – Worm Bins
Home Composting – Worm Bins
Let worms eat your scraps
Wormswaste by digesting it and converting the nutrients into a form plants can use. They excrete worm casts which are rich in humus and a fine crumby texture which is ideal for potting compost as well as enricher. Worm pee is also an extremely powerful fertiliser.
Most compost systems require a bit of space, or effort, or both, plus a reasonable amount of waste. But wormrequires only room for a box, takes little time or effort, and the worms only need kitchen scraps which they recycle into very rich crumbly compost and liquid fertiliser. Worm bins are ideal for small families with urban gardens, even balconies or roof gardens. Keen recyclers who only have houseplants and windowboxes can use them because worm bins can even be kept indoors— as long as a bin is working properly it won’t give off any offensive smells or attract bugs.
Like conventional compost systems, worm bins need warmth, air and moisture. Worms have to have moist skin in order to breathe, they need air so the material doesn’t get waterlogged and smelly, and they are most productive between 18-28°C so a bin needs to be well insulated if it lives outside in winter, and shaded in summer. The best times to start a worm bin are spring and summer when temperatures are ideal and worms are hungriest. Provide your worms with moist crumbly bedding and keep them in the dark. They also need a slightly alkaline environment so keep an eye on their diet (see below).
Unlike other compost systems, worms need feeding little and often, not much bulk —they are much more likely to die from overfeeding than from starvation. Worms will eat almost anything as long as it is chopped small, but concentrate on kitchen scraps – they won’t destroy perennial, weed seeds or diseased plant material.
Like other compost containers, a worm bin should keep moisture in and rain out, allow some air to circulate, and be able to maintain a fairly constant temperature. You can buy a custom-built plastic bin or wooden box complete with worms, but it is more economical and not difficult to recycle an old box or large drawer, or convert a plastic dustbin. Worms are freely available in muck heaps or from fishing tackle shops.
A worm bin doesn’t need to be very tall, but choose a wide container rather than a narrow one as worms feed near the surface so the greater the surface area the more compost they’ll produce.
Wooden or plastic
An ideal size wooden box is around 6ocm square and 3ocm tall. Never use chemically treated wood. Simply drill some holes in the base for drainage and line the box with a single layer of pebbles before adding worm bedding. Find or make a lid, which should have cracks for air.
If you convert a dustbin drill two lines of drainage holes about 10cm and 15cm from the base, and make ventilation holes in the lid, which should fit tightly for insulation and to stop flies. To keep humidity fill the bottom iocm with pebbles and sand, and add water until it seeps from the drainage holes. Put the bedding on top of the pebbles — you may want to lay gauze first so the bedding and compost remains slightly separate from the stones.
There won’t be much seepage from a wooden box so a newspaper underneath the box should be sufficient to stop puddles. But plastic bins will leak. Commercial bins are often fitted with a tap for siphoning off the liquid, which can be diluted 10:1 and used as liquid feed. Place a tray under a home-made bin and either drain it regularly to catch the more dilute liquid, or place a layer of compost on it and change it every two or three weeks, using the moistened compost on houseplants or in the garden.
Mix up a bucketful of well-rotted compost, muck or leaf-mould (but not made from beech or oak leaves as this tends to be acidic) with some shredded newspaper. Moisten the mixture thoroughly then lay this bedding about 10cm deep over the pebbles, and your worm home is ready for occupation. You’ll need at least 100 worms to start your colony. If you collect them from a compost heap bring a little of this material with them, otherwise just lay your worms in the centre of the bedding, and cover them with a couple of layers of moist newspaper.
Worms will eat any kitchen scraps but don’t give them too much citrus fruit or acid food. Chop scraps finely —some people liquidise them but this isn’t strictly necessary. Worms can eat any cooked remains, including meat and fish scraps, but can’t eat very dry food.
Worms don’t like too much food at once, so start with no more than I litre or 50o grams of finely shredded food spread on top of the bedding around 5cm deep. Don’t cover the whole surface. You can partially bury food but then it’s hard to tell when to add more, and worms are not deep feeders so some buried scraps may not get processed. Wait until the previous offerings have been well integrated before adding more. Keep the food moist and always cover it with moistened newspaper.
You can remove compost a little at a time whenever you want, but if you want to wait for a binful — the speed depends how much food is added, how many worms you have, and the temperature — empty it in spring or summer so you can get your colony going again quickly. Remove the worms in a small amount of compost and leave them on one side, covered with moist newspaper, empty the bin, and put the worms back in to start again. If you have masses of worms, start two colonies.
If your bin starts to smell it means the worms aren’t processing the food quickly enough. Reduce feeding — make a second bin if you have too many scraps — and check the moisture, temperature and pH of the compost.
If the contents of the bin get soggy check the drainage holes aren’t blocked. Mix in shredded newspaper or coir to soak up excess moisture, and don’t add extra liquid in the worm food.
Sometimes worms gather round the lid of the bin. If there are just a few this is nothing to worry about, but if they all seem to be trying to escape check pH, moisture, ventilation and temperature, and be careful about feeding. You can remove the worms, with a little compost, and cover them with moistened newspaper while you clear out the bin and start again.