Worm Composting


General information

Worms can compost rubbish faster than any other type of composting method. Worms also are very efficient in digesting kitchen food wastes. Each day a worm eats half its weight in food. The care and feeding of worms take far less effort than maintaining an outdoor compost pile. Some of the benefits of keeping a worm bin include: recycling kitchen food waste, reducing waste disposal costs, producing soil amendments or fertiliser for house and garden plants, and having a ready supply of fishing worms.

A worm bin is a self-contained system. As with any system, several components are involved.

Red worms are the most satisfactory worms to use in a home vermicomposting (composting with worms) system. The species of red worm best suited for a worm bin is Eisenia foetida pronounced "I see nee a fet id a." Eisenia Foetida is known by several common names: red worm, brandling worm, red wriggler, manure worm, and fish worm among others. Starter worms of this species for a worm bin may be found in old compost piles (ones that no longer generate any heat) or from local bait suppliers.

Once the worm bin is constructed, make bedding for the worms with shredded and moistened newspaper or cardboard. Maintain the system by burying food wastes throughout the bin on a rotational basis. Every three to six months move the compost to one side of the bin and add new bedding to the empty half. The worms will soon move to the new bedding. Harvest the compost and add new bedding to the rest of the bin.

How You Do It

This system is composed of a box to contain the worms (see back for a description of how to build a worm bin); the worms themselves; a controlled environment; and regular maintenance procedures. Worm compost is made in a container filled with moistened bedding and red worms. Add food waste and with assistance from micro-organisms, the worms will convert bedding and food waste into compost. Worm composting can be done year-round, indoors in schools, offices and homes. It is a natural method for recycling nutrients in food waste without odour. The resulting compost is a good soil conditioner for houseplants, gardens and patio containers.

What You Need

  1. A container (made of wood or plastic)
  2. Worms (500-2,000 red worms)
  3. Bedding (shredded newspaper, corrugated cardboard and/or leaves)
  4. Kitchen waste (fruit and vegetable waste)

1. The Container

Buy or build a container (see How to Make a Wormbin) or use an old dresser drawer, box or barrel. Wood containers are absorbent and good insulators for worms. Plastic containers do work but compost tends to get quite wet and may need more drainage. Raise the bin on bricks or wooden blocks for air circulation. Place a tray underneath to capture excess liquid, which can be used as liquid plant fertiliser. Some newer containers replace drainage holes in the bottom with a venting system higher in the container.

Worms like a moist, dark environment. Their bodies are 75 to 90 per cent water and worms' body surfaces must be moist for them to breathe. Cover the bin to conserve moisture and provide darkness. Indoors, place a sheet of dark plastic or burlap sacking on top of the bedding. Outdoors, use a solid lid to keep out unwanted scavengers and rain.

Worm bins can be located in a cellar, shed, garage or balcony. They need to be kept out of the hot sun, heavy rain and cold. When temperatures drop below 4 degrees C, bins should be kept in a frost-free place, heated or well insulated. The container can be heated with an electric heating cable placed in the bottom third of the container. To insulate, surround the container with (5 - 7.5cm.) rigid polystyrene, which can be bought from a builder's merchant.

2. The Worms

Red worms are best suited to worm composting. They are often found in aged manure, compost heaps, and piles of leaves. They are also known as red wriggler, brandling and manure worms. Their official names are Eisenia foetida and Lumbricus rubellus. Red worms are best suited for composting because they thrive on organic material, such as food waste. Earthworms, on the other hand, are better suited to life in the soil and shouldn't be used in a worm bin.

You can get your worms from an existing compost bin, purchase them or find a horse stable or farmer with an aged manure pile.

Red worms mature sexually in 60-90 days and can then produce cocoons, which take 21 days to hatch baby worms. Once they start breeding they can deposit two to three cocoons per week with two baby worms in each cocoon. The limits on their reproduction include availability of food and room to move and breed. So worm populations don't usually exceed the size of the container.

3. The Bedding

Provide damp bedding. Suitable bedding material includes shredded newspaper and cardboard, shredded fall leaves, chopped-up straw and other dead plants, seaweed, sawdust, dried grass clippings, aged manure and peat moss. Peat moss is quite acidic and should be well soaked and combined with other bedding material. Vary the bedding in the bin to provide more nutrients for the worms and to create richer compost. Two handfuls of sand or soil will provide the necessary grit for worms' digestion of food.

Fill the bin with a mixture of damp bedding so the overall moisture level is like a "wrung-out sponge." Lift the bedding gently to create air spaces. This maintains aerobic activity, helps control odours and gives the worms freer movement.

4. The Food Waste

Your worms will eat any soft organic food scraps such as vegetable waste generated during food preparation, potato peelings, vegetable peelings, grapefruit and orange rinds, cantaloupe and watermelon rinds, outer leaves of cabbage and lettuce. Plate scrapings, spoiled food from the refrigerator, coffee grounds, tealeaves or eggshells are wastes that you may want to feed your worms.

To avoid potential rodent problems do not add cooked meats; decaying meat can produce offensive odours, dairy products, oily foods or grains.

Needless to say such things as glass, plastic, tin foil, wire ties, bottle caps, rubber bands and heavy shiny type paper should not be put in the wormbin.

For the first couple of weeks, collect food wastes in a container and weigh it. Do this for two weeks to get an estimate of average food waste. Your bin should provide one square foot of surface area for every pound of food waste per week. And you will need two pounds of worms for every pound of food waste per day. Once the worm colony has settled down and established itself, the waste can be put directly in the wormery.

Harvesting Your Compost

After six weeks, the bedding will be noticeably darker with worm castings. After two and a half months have passed, there will still be some of the original bedding visible in the bin plus brown and earthy-looking worm castings. Although food waste is being added regularly, the bedding volume will gradually decrease. As more bedding is converted into castings the worms will begin to suffer. It is time to decide whether you want to do "some fuss" or "more fuss" worm composting.

"Some Fuss" Harvesting

Some fuss worm composting involves moving the finished compost over to one side of the bin, placing new bedding in the space created, and placing food waste in the new bedding. The worms will gradually move over to the fresh bedding and food waste, and the finished compost can be harvested. Fill the space created with new damp bedding.

"More Fuss" Maintenance

If you want to use all of the compost at once, dump the bin's entire contents onto a large plastic sheet and make piles of material. Use sunshine or a hundred watt light bulb to drive the worms to the bottom of the piles. Worms don't like bright light because the single cells on the epidermis (skin) react to light. Scoop off the tops of each pile until all you have left is the worms. Most children love to help! Watch out for the tiny, lemon-shaped worm cocoons that contain the baby worms. Mix a little of the finished compost in with the new bedding of the next bin.

Show a Little Respect

We must act responsibly if we take worms out of their natural environment and place them in containers. They are living creatures with their own unique needs, so it is important to create and maintain a healthy habitat for them to do their work. If you supply the right ingredients and care, your worms will thrive and make compost for you.

Common Problems

Unpleasant Odours
Unpleasant odours may waft from your bin when it is overloaded with food waste. If this occurs, gently stir up the contents to allow more air in. Stop adding food waste until the worms and micro-organisms have broken down what food is already in the bin. Check the drainage holes to make sure they are not blocked and drill more holes if needed. If the moisture level seems right, the bedding may be too acidic from citrus peels and other acidic foods. Adjust by cutting down on acidic wastes.

Fruit Flies

Fruit flies aren't harmful, but they are a nuisance, and a very common problem with worm bins. Discourage fruit flies by always burying the food wastes and not overloading the bin. Keep a plastic sheet; piece of old carpet or a lid on the compost's surface in the bin. Unfortunately there is no easy answer to the fruit fly problem but adding a spider or two helps reduce fruit flies. If flies persist, move the bin to a location where flies will not be bothersome.

© copyright 1999, P. A. Owen

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