Vermiculture

The use of earthworms to produce high-quality compost is known as vermiculture. Many species of earthworms can be employed to turn food waste and animal dung into a nutrient-rich and fertile growing medium; the worms eat the food they are provided and excrete casings that can be dried and filtered for use in agriculture or soil remediation.

Production of worm castings
To produce vermicompost, a mixture of dung, water and filtered food waste is placed in a pile. Both raw and cooked food waste can be used but meat and animal products should be avoided as they will attract vermin. Earthworms are added to the pile and it is watered regularly. Once the mixture has begun to be consumed by the worms, subsequent layers are added until the desired height is achieved.

After some time the outer layer of the worm pile will have been entirely consumed, leaving only the casings and resembling roughly-ground, damp coffee. The casings can then be harvested.

To harvest the vermicompost, remove around 10mm from the top of the pile. If the worms are exposed, gently replace the casings to cover them; worms close to the surface indicates undigested food waste. The harvested casings can then be filtered using a rotating mesh drum, or a screen. Often several grades are separated; the finest grains are the most desirable and fetch the highest price when sold.

Worms for soil remediation
Worms are also reported to metabolise or filter, by some method, the heavier elements present in the inks used for many packaging and paper products. When ink-containing media are fed to the worms, such as shredded newspapers, the produced casings contain none of the metals present in the ink. As such, worms may also be used as a bioaccumulator for unwanted waste products.