Vermicomposting methods

The most widely used vermicomposting system, worldwide, is the 'bed' method, which involves applying thin layers of sanitised and partially matured compost, to the surface of beds containing high densities of earthworms.

New layers of waste are applied to beds on a regular basis and the earthworms move upwards into the fresh waste to feed and to process the material.

Earthworm numbers increase as more waste is applied until a limiting density is reached. The earthworms are then harvested or the beds are divided. Harvesting earthworms by hand can be a very time consuming business and although in principle trommel screens would be suitable, these are seldom used.

The top 100 mm to 150 mm of the compost bed soil is removed regularly and is the worm compost sold.

How long does it take to make mature vermicompost?
It is difficult to compare directly composting with vermicomposting in terms of the time taken to produce stable and mature composted products.

With vermicomposting, particles of waste spend only a few hours inside the earthworm's gut and most of the decomposition is actually carried out by micro-organisms, either before or after passing through the earthworm. Hence, earthworms accelerate waste decomposition rather than being the direct agent.

With windrow composting, it usually takes at least six to twelve weeks to produce a stable compost, and research suggests that vermicomposting takes about the same length of time.

However, processing rates will depend on many factors such as the system being used, the nature of the wastes and the ratio of earthworms to waste.