What you need and how you do it
- The Container
Firstly you will need to obtain one or more suitable worm containers, which may be either plastic, wood or metal. Use your imagination and recycle an old bath tub or wooden box, drawer or a plastic basin, bin or crate, or alternatively buy or build one. Wooden containers provide good insulation and, because they are absorbent, excess moisture in the wormery may be less of a problem. Plastic containers are convenient but have a tendency to keep the compost too wet at times. Experiment and find out what works for you and your worms.The container should ideally be 20-40 cm deep with a relatively large surface area (about 40 x 4060 cm), because worms like to work near the surface. A shallow container also allows for better aeration of the bedding. As a guide allow approximately 2000 cm surface area (or a volume of 60 litres) for every 200 grams of food waste per day.You can calculate the amount of waste you generate daily by collecting potential worm food in a container for one week, weighing it, and then dividing the weight by 7.Depending on size, drill or punch 8-12 holes about 10 mm diameter in the bottom of the container for aeration and drainage. Worms need air to live. If contents become too wet, drill more holes. Bins should be raised up on bricks or wooden blocks to aid air circulation and drainage. By placing a plastic tray underneath to capture excess liquid, you can obtain an excellent liquid plant fertiliser - use diluted at the rate of 1 part liquid to 10 parts water.Cover the bin to conserve moisture and provide a dark environment for the worms.Consider using several containers for ease of lifting and moving.
- Worm Bin Location
Locate your worm bins where access is convenient. Bins can be kept in sheds and garages, on verandas, patios, porches, balconies or in the backyard. A sheltered spot that gets some sun is ideal, but be careful as a bin in full sun may get too hot, especially in summer. When outside temperatures drop below 10C, bins should either be moved inside or kept well insulated if left outdoors. Wrapping carpet or something similar around the bin for insulation will help prevent the worms from freezing during the winter.
- The Worms
Two species are especially suited for worm composting, namely Tiger Worms Eisenia fetida and Red Worms Lumbricus rubellus (which are also known as red wriggler or manure worms). These types thrive on moist organic materials such as food scraps, eating as much as their own weight per day. The recommended ratio of worms to food is: for about 400 grams per day of food waste (a typical amount for a family of four to six), use a minimum of 500 grams of worms (just over 1000 worms) and preferably 900 grams (about 2000 worms). It doesn't matter if you are unable to obtain this number of worms initially - just reduce the quantity of food fed accordingly. If you provide ideal conditions, the worm population will steadily increase, doubling their numbers every 40 or so days.
Where to obtain your worms
You can check yours or a friend's compost heap for worms, visit horse stables or a farmer with a mature manure heap or order them online or via a retailer.
- The Bedding
The worms require a moist bedding in which to live and lay their eggs. Suitable materials include shredded and moistened newspaper (avoid coloured print, and tear newsprint into strips about 25 mm wide) as well as cardboard, peat, straw, aged manure or compost. Sawdust is not recommended due to its resin content. Experiment with different bedding materials, for worms like a varied diet. A mixture of ingredients is quite acceptable.Addition of one or two handfuls of coarse sand or topsoil (preferably silty loam) will provide the grit that the worms need to grind their food. Three quarters fill the worm bin with damp bedding that has the consistency of a squeezed out sponge. It must be moist but not soggy. Gently place bedding in position avoiding compaction, as air spaces are necessary for successful composting, helping to control odours and facilitating freer movement and air for the worms.
- Suitable Worm Food
Worms are omnivorous, eating both plants and meat tissue, so most organic waste can be composted. They will eat most kitchen vegetable/fruit scraps or peelings, shredded paper, eg; handy towels, tea bags/leaves, coffee grounds/filters, crushed egg shells, bread scraps, leftover cereal, cottage cheese, plate scrapings, biscuit crumbs, even ice cream. Meat/fish scraps and dairy products may also be used, but feed in moderation, making sure you bury (not too deeply) them in the bedding to stop odours and discourage flies. Meat and fish scraps are not recommended until you are familiar with worm composting. If odours are troublesome, these ingredients are best left out. It is beneficial to occasionally add a little semi-mature compost (past heating stage), aged horse manure or similar to your system. This provides a source of decomposer micro-organisms which help to soften the food for the worms, as well as providing additional food.
Food to avoid
- Citrus or acidic fruits such as oranges, lemons, grapefruit and kiwifruit are best avoided, or used sparingly, as these make the conditions too acid for the worms.
- Garden waste is generally not suitable for these worms, also materials such as grass clippings may heat up quickly, which the worms will not appreciate, and it may even kill them. Garden waste is best dealt with by conventional composting methods.
- Fats, cooking/salad oils and oily foods should be avoided as these create slimy conditions, odour and fly problems.
- Use of tough woody material is not recommended unless chopped into small pieces.
- Do not use onions, garlic or hot spicy food scraps.
- Bones, glass, plastic, tinfoil or other inert materials.
- If adding aged (composted) manures to your wormery, avoid chicken manure as this tends to be too acidic for the worms.Also
- Harvesting the compostAs time passes, the bedding, along with the food waste, is converted into worm manure (castings). It becomes heavier, more compact and changes to a dark brown soil-like material. This stage is usually reached within three to four months. The quality of the worms' environment is diminished, as they have effectively fouled it with their manure. For the health of the worms and continued efficient wormery operation, it is time to remove some, or all, of the finished compost. There are several ways of doing this - discover which is best for you. Here are some ideas:
- The easiest method consists of removing, with a hand fork, the top 150 mm worm rich layer, and setting this aside for seeding the next bin. The remaining contents can then be removed for either immediate use or stored until required. Addition of the top layer back into the container with fresh bedding starts the whole process again. Alternatively,
- Tip the entire contents of the bin onto a plastic sheet or a concreted area (best done outside). Spread the compost out to form a layer about 100 mm thick. The worms dislike light and burrow deeper into the compost to avoid it. Slowly remove the compost in layers, until eventually you have a mass of wriggling worms which can be added back into the worm bin containing new bedding.
Be careful that the worms don't dry out
You may wish to manually separate out the worms. Children usually love this! Watch for small worms and the tiny (average around 4 mm) yellow/pink oval shaped cocoons, which may contain baby worms.
- You may prefer to simply move the finished compost over to one side of the bin, place fresh bedding in the space created, and add food waste to the new bedding only. The worms will gradually move over and the compost can then be removed. At this stage you may wish to start extra worm bins or give some worms to a friend.