Vermicompost (vermi-compost) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and vermicast. This process is called vermicomposting, with the rearing of worms for this purpose is called vermiculture. Vermicast (also called worm castings, worm humus, worm poop, worm manure, or worm faeces) is the end-product of the breakdown of organic matter by earthworms. These excreta have been shown to contain reduced levels of contaminants and a higher saturation of nutrients than the organic materials before vermicomposting. Vermicompost contains water-soluble nutrients which may be extracted as vermiwash and is an excellent, nutrient-rich organic fertilizer and soil conditioner. It is used in gardening and sustainable, organic farming. Vermicomposting can also be applied for treatment of sewage. A variation of the process is vermifiltration (or vermidigestion) which is used to remove organic matter, pathogens, and oxygen demand from wastewater or directly from blackwater of flush toilets.
Overview Vermicomposting has gained popularity in both industrial and domestic settings because, as compared with conventional composting, it provides a way to treat organic wastes more quickly. In manure composing, the use of vermicomposting generates products that have lower salinity levels, as well as a more neutral pH. The earthworm species (or composting worms) most often used are red wigglers (Eisenia fetida or Eisenia andrei), though European nightcrawlers (Eisenia hortensis, synonym Dendrobaena veneta) and red earthworm (Lumbricus rubellus) could also be used. Red wigglers are recommended by most vermicomposting experts, as they have some of the best appetites and breed very quickly. Users refer to European nightcrawlers by a variety of other names, including dendrobaenas, dendras, Dutch nightcrawlers, and Belgian nightcrawlers. Containing water-soluble nutrients, vermicompost is a nutrient-rich organic fertilizer and soil conditioner in a form that is relatively easy for plants to absorb. Worm castings are sometimes used as an organic fertilizer. Because the earthworms grind and uniformly mix minerals in simple forms, plants need only minimal effort to obtain them. The worms' digestive systems create environments that allow certain species of microbes to thrive to help create a "living" soil environment for plants. The fraction of soil which has gone through the digestive tract of earthworms is called the drilosphere. Vermicomposting is a common practice in permaculture. Vermiwash can also be obtained from the liquid potion of vermicompost. Vermiwash is found to contain enzyme cocktail of proteases, amylases, urease and phosphatase. Microbiological study of vermiwash reveals that it contains nitrogen-fixing bacteria like Azotobactrer sp., Agrobacterium sp. and Rhizobium sp. and some phosphate solublizing bacteria. Laboratory scale trial shows effectiveness of vermiwash on plant growth.
Design considerations
Suitable worm species All worms make compost but some species are not suitable for this purpose. Vermicompost worms are generally epigean. Species most often used for composting include:
Eisenia fetida (Europe), the red wiggler or tiger worm. Closely related to Eisenia andrei, which is also usable. Eisenia hortensis (Europe), European nightcrawlers, prefers high C:N material. Eudrilus eugeniae (West Africa), African Nightcrawlers. Useful in the tropics. Perionyx excavatus (South and East Asia), blueworms. May be used in the tropics and subtropics. Lampito mauritii (Southern Asia), used locally. These species commonly are found in organic-rich soils throughout Europe and North America and live in rotting vegetation, compost, and manure piles. As they are shallow-dwelling and feed on decomposing plant matter in the soil, they adapt easily to live on food or plant waste in the confines of a worm bin. Some species are considered invasive in some areas, so they should be avoided (see earthworms as invasive species for a list). Composting worms are available to order online, from nursery mail-order suppliers or angling shops where they are sold as bait. They can also be collected from compost and manure piles. These species are not the same worms that are found in ordinary soil or on pavement when the soil is flooded by water. The following species are not recommended:
Lumbricus rubellus and Lumbricus terrestris (Europe). The two closely related species are anecic: they like to burrow underground and come up for food. As a result, they adapt poorly to shallow compost bins and should be avoided. They are also invasive in North America.
Large scale Large-scale vermicomposting is practiced in New Zealand, Canada, Italy, Japan, India, Malaysia, the Philippines, and the United States. The vermicompost may be used for farming, horticulture, market gardening, landscaping, to create compost tea, or for sale. Some of these operations produce worms for bait and/or home vermicomposting. There are two main methods of large-scale vermicomposting, windrow composting and raised bed. Some systems use a windrow, which consists of organic feedstock for the earthworms to feed on. Earthworms will move into the windrows and remain within them as long as conditions are favourable; typically involving a balanced mix of feedstock, appropriate moisture content and a comfortable temperature. Often windrows are used on a concrete surface to control and manage leachate. The world's largest vermicomposting operation by volume is MyNoke, a New Zealand–based operation that has processed over 1.4 million tonnes of organic waste since establishment in 2007. Windrow turners were developed by Fletcher Sims Jr. of the Compost Corporation in Canyon, Texas. The Windrow Composting system is noted as a sustainable, cost-efficient way for farmers to manage dairy waste.
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