You can easily make a worm bin out of large buckets, polystyrene trays or an old bath.
If you use a bath, remove the plug. If you want to, you could build a frame to allow the bath to sit securely at waist height. Bricks, posts or blocks may be used for elevation, and for stability, ie, 100-150mm height (allowing room for the liquid collection container placed beneath plug outlet). The plug outlet end must be no less than a 5 degree fall to the lowest point to achieve adequate drainage. Roofing such as ply or corrugated iron will be needed to shed water and provide protection from summer sun.
Place into the base of the bath 1.5m of 65mm perforated drainage pipe with two layers of old stockings. This seals the ends and covers the perforations which stops the pipe blocking. Add pumice sand or scoria to a depth of 75mm then place shade cloth, doubled over and cut to fit, on top of filtering layer.
A free draining fibrous matured compost is ideal given that it is not going to produce heat. Dampened shredded corrugated cardboard and lunch paper gives increased air availability and reduces the risk of bedding material heating up. You need to water well and leave at least two days. Then check for temperatures over 25 degrees. If there are any unpleasant odours, apply two handfuls of garden lime and mix in. Avoid fresh lawn clippings. As fresh clippings heat up and cook the worms, only apply old lawn clippings.
For quick results, 500g-1kg (2000-4000 worms) should be enough for your worm farm to cope with 400gms to 800gms of mixed food waste each day. This volume will increase as the worms multiply. Spread worms on to bedding and spread food scraps in one area rotate feed sites.
As the bath fills use garden fork and loosen bedding, this increases air circulation and reduces bedding compaction.
To remove the casts, once the worm farm is full (after nine to 18 months), place a plastic sheet or large container next to the bath, and using a garden fork remove the top half of the worms’ bedding. This is undigested food and is where the majority of worms will be. Place this to one side.
Remove all casts. Rinse drainage layer thoroughly catching all liquid.
Replace the contents that were put aside and commence the feeding, forking, watering process when required.
Your bath worm farm will ultimately digest about 1-2 litres of mixed organic waste a day.