Vermicomposting, or composting with earthworms, offers a way to recycle organic waste produced in the home kitchen and the yard. It requires relatively little space, and thus is an option for apartment dwellers or winter composters. With vermicomposting, the worms do the aeration for you, so you don't even have to turn the compost.
A vermicompost bin, ideally a covered container no more than 12 inches deep, contains moistened bedding material, composting worms, and organic waste. The waste usually takes the form of fruit and vegetable scraps that a family adds to the bin as they accumulate. Bin contents are about three-quarters bedding materials, such as shredded newspaper or cardboard, shredded leaves, hay, straw, or peat moss. Bedding high in cellulose, like cardboard, promotes good aeration letting the worms can breathe easily.
Not just any old earthworm will do for vermicomposting. Either brandling worms or redworms, also known as tiger worms or red wigglers, are needed. Often naturally found in aged manure piles, these types of worms are available from lawn and garden companies. It takes about one pound of composing worms to process a half-pound of kitchen scraps per day. As the worms consume organic material, it passes through their guts and comes out as nutrient-rich castings, which look like fine textured soil.
Food scraps are added to the bin for about three months or until the bedding material has disappeared. Once the worms have turned the food scraps and bedding into a nice rich organic material with an earthy smell, it is time to remove or harvest the vermicompost. It may be top-dressed on lawns, used for potted plants, added to enrich garden soil, or put to use as mulch.
The nutrients in vermicompost are usually found at notably higher levels than those found in regular garden compost, according to the New Mexico State University Cooperative Extension. One of the most striking contrasts is in nitrate nitrogen. Vermicompost contains 902.2 parts per million nitrate nitrogen, while garden compost has a mere 156.5 parts per million.
Adding too much food waste to the bin could cause odor problems. If a foul odor is emanating from the bin, stop adding scraps until the worms can catch up.
Vermicompost bins require a cover to keep insects and rodents out. Pest problems are also reduced by making sure the scraps are buried in the bedding.
If the bin contents are too wet, it may attract the earthworm mite, which could cause the worms to stop eating. Discourage the mite by making sure the bin has adequate drainage on the bottom.