A wormery is an efficient, easy and environmentally friendly way of converting ordinary garden and kitchen waste into solid compost, known to gardeners as 'black gold', and concentrated liquid feed, through the natural action of worms.

Over millions of years, worms have evolved into fast and efficient detrivores. A detrivore is any organism, other than bacteria or fungi, that feeds on large bits of dead and decaying organic matter. The matter that is left behind by detrivores is further broken down by decomposers. Each worm eats and digests up to half its own body weight in waste every day, thus greatly decreasing the volume of the waste.

The liquid waste will need to be diluted about one part in ten with water before adding it to your plants. The solid matter, known as 'vermicompost' can be spread directly onto your garden.

Background

It is estimated that each person in the UK generates about 500kg of waste per year, and that each household throws away over a tonne of waste annually. Around 70% of our household waste has the potential to be either recycled or composted. Despite the fact that the majority of the general public regard recycling as worthwhile, and that over 65% of households in the UK have access to kerbside collection recycling schemes, only 14.5% of dustbin contents are actually recycled or composted. Many local authorities offer compost thus generated for sale to the public.

Recent evidence has suggested that, although people are aware of and concerned about environmental issues, they are most likely to take action when it 'hits them in the pocket'. For example, in August 2006, the UK national press was reporting that householders could soon be charged by the kg for rubbish they leave out for collection, as part of a shake-up of local government finance; although recyclables would be collected for free. Nevertheless, for those households which have a garden or access to an allotment, 'home composting', is an attractive proposition.

Equipment

The equipment to create a wormery can be purchased, and consists of a large plastic bin (about the size of a wheelie bin) with a tight-fitting hinged lid¹ containing airholes and an internal perforated platform to separate the liquid waste from the solid. The bin is fitted with a tap at the bottom in order to withdraw the liquid.

The worms are not ordinary garden earthworms (Lumbricus terrestris), which are soil-dwellers and would not survive in a wormery, but are a mixture of British native species of composting worms called tiger worms (Eisenia andrei), red worms (Eisenia foetida) or brandlings (Dendrabeana venera). These can be obtained from most fishing shops or by mail-order from worm bin manufacturers or organic gardening suppliers.

One of the main reasons for wormeries not functioning efficiently is that they can become too acidic, and therefore a poor environment for worms. This can be prevented by occasionally adding calcified seaweed and/or crushed eggshells. Another useful resource is ash from the garden bonfire². Here, one should only burn material that cannot easily be composted, for example thick, thorny material such as prunings, brambles and thorn hedges. The garden bonfire is also useful for destroying persistent weeds such as couch grass, ground elder and bindweed. Failing these, you can also add ground lime or dolomite - but not ordinary garden lime which could harm the worms.

Getting Started

As a properly maintained wormery should be odour-free, there is no reason that a wormery cannot be placed right outside your kitchen door if necessary or desired. Indeed, vermicomposting is particularly suitable if you live in a flat without a garden, or if there is insufficient space in your garden for a conventional compost heap.

Place a single sheet of newspaper (about 20cm square) onto the separating platform and cover this with shredded newspaper³ which has been slightly dampened with water.

A small pile of compost is added, which may be dampened sedge peat (moss peat is too acidic)⁴ or a peat substitute such as coir, leaf mould or some well-rotted sterile compost.

The worms⁵ are now placed into the middle of the bedding, together with a thin layer (three or four handfuls) of kitchen waste. The lid should be left open for ten minutes or so, so that the light will encourage the worms to dig into the bedding. Further food should not now be added for a week.

Maintenance

Once the worms have settled, they will speed up their activity - provided the weather is not too cold. For the next two weeks after setting up one should only add three to four handfuls of kitchen waste each week. Following this, your wormery will be ready for normal operation, and one can simply add kitchen waste at the rate it becomes available. Ideally, food should be added every day. In the case of fibrous or woody waste such as cauliflower and cabbage stalks, it is best to chop this up. Now and again it is beneficial to occasionally mix the fresh waste in with the older contents to ensure that the worms spread through the surface layers.

The appearance of tiny cotton thread-like white worms⁶ is indicative of the wormery having become too acidic. Addition of calcified seaweed, well mixed in, with some shredded newspaper should be enough to restore the balance.

Overwintering

Worm activity slows significantly below about 8°C, and ceases below about 5°C. However, in this Researcher's experience, if the wormery is sufficiently full at the start of winter, the heat generated by decomposition is sufficient to prevent the internal temperature of the wormery from becoming too cold. If it is available, your wormery can be insulated with old carpet. However, if you are concerned about temperature or if the winter is forecast to be particularly harsh, then it is advisable that you place your wormery in an outbuilding such as the garden shed, utility room or garage.

At the other end of the scale, tigerworms may not survive if the temperature goes above about 40°C.

Using your Compost

When the bin is nearly full and has been properly composted it will have a dark, spongy, soil-like appearance. Remove the worms, which will usually be in a layer just below the surface, and place them temporarily in a bucket or other suitable container. The compost may then be emptied out of the bin at the point of use (ie, as a top dressing or mulch) or saved for use as an ingredient for making up your own potting compost.

The worms should be replaced into a freshly set-up wormery and used for making the next batch of compost. It is usually possible to harvest worm compost from your bin about every four to nine months.

Is there Anything that can't be Composted?

Most kitchen and garden waste can be added to your wormery. However, in common with normal composting, it's best to avoid the following:

• Meat and fish
• Cheese
• Baked beans
• Rice or pasta
• Cooked potatoes
• Too much highly acidic food, such as citrus fruits and onions
• Grass in too much quantity
• Weed seeds
• Diseased plant material
• Dog or cat excrement, as this can contain human parasites (This Researcher uses a 'Dog Waste Digester').