Vermicomposting: Earthworms in Action

What is vermicomposting and how is it undertaken? Few of us think of earthworms as domesticated animals that produce useful products, but the efforts of Canon Savala of FORMAT show us how to make good use of this humble, but very important creature.

Vermicomposting is the processing of organic wastes using earthworms. Earthworms ingest and transform organic residues into high quality humic material.  A useful procedure for vermicomposting at home or on small farms follows:

1. Construct the bed. Prepare a bed with a concrete, wood or plastic sheet bottom and construct walls 20 to 30 cm in height using wood, logs or stone. 

2. Add coarse material. Place a 10 to 15 cm layer of coarse organic materials such as banana trash, maize stover, coffee husks and other crop residues on top of the chicken wire placed on the floor of the bed (right).

3. Add fine material and water. Place a 5 to 10 cm layer of manure on top of the coarse material. Cattle, pig, sheep or goat manure are suitable.  Green manure, such as tree leaves or grass cuttings may be substituted.  Moisten the organic materials prior to the introduction of the worms. 

4. Release worms. Release the earthworms into the moist bed.  Avoid handling individual worms, rather place small handfuls of material rich in earthworms (clusters) into “holes” spaced about 0.5 m apart.

5. Cover the bed. Cover the bed with banana leaves or dark polythene plastic. Inspect the bed regularly during composting for moisture and the presence of predators, particularly ants. Add new layers of banana leaves occasionally as the worms consume older leaves.

6. Feed the bed.  Organic materials may be applied to the bed regularly as additional layers or in discrete locations.  A common practice is to periodically apply additional organic wastes by burying them in different positions within the bed. Vermicompost is ready after three to six months.

7. Recover worms and compost. When the vermicompost is ready, worms are harvested and compost processed. Collected worms may also be fed to fish and poultry. Spread vermicompost in the sun to collect remaining pockets of worms by hand as it dries (below).

In this way, earthworms are useful in organic waste recycling. A typical nutrient content of the compost is 1.9% nitrogen, 0.3% phosphorus and 2.7% potassium.  Screened vermicompost serves as an excellent potting media. After vermicomposting, the worms may also be recovered for use as fishing bait or poultry feed.   Keep in mind that  vermicomposting requires the use of specialized worms that feed on plant litter, known as epigeics.   More information on vermicomposting is available in the book “Organic Resource Management in Kenya”.  Earthworms provide an excellent source of protein that could even be consumed by humans but current food preferences tend to discourage this practice.  Worm burger anyone?