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Rotary screen harvested worm castings

Vermicompost, or Vcompost, is the heterogenous mixture of decomposing vegetable or food waste, bedding materials, and pure vermicast produced during the course of normal vermiculture operations. Vermicast, similarly known as worm castings, worm humus or worm manure, is the end-product of the breakdown of organic matter by some species of earthworm.

Containing water-soluble nutrients and bacteria, vermicompost is an excellent, nutrient-rich organic fertilizer and soil conditioner.[1] The process of producing vermicompost is called vermicomposting.


[edit] Suitable species

The earthworm species (or composting worms) most often used are Red Wigglers (Eisenia foetida), but European nightcrawlers (Eisenia hortensis) and more acid tolerant worms called dendrobaenas or dendras may also be used.

Blueworms (Perionyx excavatus) may be used in the tropics[2].

These species are commonly found in organic-rich soils throughout Europe and North America and live in rotting vegetation, compost and manure piles. They may be invasive in some areas[3][4].As they are shallow-dwelling and feed on decomposing plant matter in the soil, they adapt easily to living on food or plant waste in the confines of a worm bin.

Composting worms are available to order online, from nursery mail-order suppliers or angling (fishing) 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 soil is flooded by water.

[edit] Large scale

Large-scale vermicomposting is practiced in Canada, Italy, Japan, the Philippines, and the United States [5][6]. The vermicompost may be used for farming, 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 vermiculture. Some systems use a windrow, which consists of bedding materials for the earthworms to live in and acts as a large bin; organic material is added to it. Although the windrow has no physical barriers to prevent worms from escaping, in theory they should not due to an abundance of organic matter for them to feed on. Often windrows are used on a concrete surface to prevent predators from gaining access to the worm population.

Movement of castings through a worm bed.

The second type of large-scale vermicomposting system is the raised bed or flow-through system. Here the worms are fed an inch of "worm chow" across the top of the bed, and an inch of castings are harvested from below by pulling a breaker bar across the large mesh screen which forms the base of the bed.

Because red worms are surface-dwellers constantly moving towards the new food source, the flow-through system eliminates the need to separate worms from the castings before packaging. Flow-through systems are well suited to indoor facilities, making them the preferred choice for operations in colder climates.

[edit] Small scale

Demonstration home scale worm bin at a community garden site - painted plywood

For using worms as a home composting solution, a large variety of bins are commercially available, or a variety of adapted containers may be used. They may be made of old plastic containers, wood, Styrofoam, or metal containers. The design of a small bin usually depends on where an individual wishes to store the bin and how they wish to feed the worms.

Some materials are less desirable than others in worm bin construction. Styrofoam is believed to release toxins into the earthworms' environment[7]. Metal containers often conduct heat too readily, are prone to rusting, and may release heavy metals into the vermicompost. Some cedars, Yellow cedar, and Redwood contain resinous oils that may harm worms[8], although Western Red Cedar has excellent longevity in composting conditions.

Bins need holes or mesh for aeration, and a spout or holes in the bottom for excess liquid to drain into tray for collection. Wormeries made from recycled or semi-recycled plastic are ideal, but require more drainage than wooden ones because they are non-absorbent. However, wooden bins will eventually decay and need to be replaced.

Small-scale vermicomposting is well-suited to turn kitchen waste into high-quality soil amendments, where space is limited. Worms can decompose organic matter without the additional human physical effort that bin composting requires.

Earthworms and bacteria are the major catalysts for decomposing food waste in a healthy vermicomposting system. Other soil species that contribute include insects, other worms and molds.[9]

[edit] Climate and temperature

Worms used in composting systems prefer temperatures of 55 to 70 degrees Fahrenheit (12-21 degrees Celsius)[citation needed]. The temperature of the bedding should not drop below freezing or rise above 89.6 °F (32 °C). This temperature range means that indoor vermicomposting is suitable in all but tropical climates. If a worm bin is kept outside, it should be placed in a sheltered position away from direct sunlight and insulated against frost in winter.[10] Some experts recommend that "backyard composters ... use or build a bottomless worm bin that sits on top of -- or better yet, is built into the ground. If the worms can escape adverse conditions by burrowing down, their survival and ... success as a vermicomposter increases greatly."[11]

It is necessary to monitor the temperatures of large-scale bin systems (which can have high heat-retentive properties), as the feedstocks used can compost, heating up the worm bins as they decay.

[edit] Feedstock

Small-scale or home systems usually use kitchen and garden waste[citation needed]. This includes:

  • All fruits and vegetables (including citrus and other "high acid" foods)
  • Vegetable and fruit peels and ends
  • Coffee grounds and filters
  • Tea bags (even those containing high tannin levels)
  • Plate scrapings, moldy bread
  • Leaves and grass clippings (not sprayed with pesticides[citation needed])

There are few food wastes that vermicomposting cannot compost, although meat waste and dairy products are likely to putrefy, and in outdoor bins can attract vermin. Green waste should be added in moderation to avoid heating the bin.

Large-scale commercial vermicomposting systems need reliable sources of large quantities of food. Systems presently operating use:

  • Dairy cow or pig manure
  • Sewage sludge
  • Agricultural waste
  • Food processing and grocery waste
  • Cafeteria waste
  • Grass clippings and wood chips
  • Shredded newspaper or cardboard as bedding

[edit] Harvesting

Worms in a bin being harvested

Vermicompost is ready for harvest when it contains few-to-no scraps of uneaten food or bedding[citation needed]. There are several methods of harvesting[which?], depending on the purpose for which the vermicompost will be used, and whether or not the composter wishes to salvage as many worms and worm eggs as possible from the vermicompost.

[edit] Properties

Vermicompost is richer in many nutrients than compost produced by other composting methods[12]. It is also rich in microbial life[which?] which converts nutrients already present in the soil into plant-available forms.

Unlike other compost, worm castings also contain worm mucus which helps prevent nutrients from washing away with the first watering and holds moisture better than plain soil[citation needed].

[edit] Benefits


  • Improves its physical structure[citation needed]
  • Enriches soil with micro-organisms (adding enzymes such as phosphatase and cellulase;
  • Microbial activity in worm castings is 10 to 20 times higher than in the soil and organic matter that the worm ingests [13];
  • Attracts deep-burrowing earthworms already present in the soil
  • Improves water holding capacity[citation needed]

Plant growth


  • Biowastes conversion reduces waste flow to landfills
  • Elimination of biowastes from the waste stream reduces contamination[citation needed] of other recyclables collected in a single bin (a common problem in communities practicing single-stream recycling.
  • Creates low-skill jobs at local level
  • Low capital investment and relatively simple technologies make vermicomposting practical for less-developed agricultural regions.


[edit] As fertilizer

Mid-scale worm bin (1 m X 2.5 m up to 1 m deep), freshly refilled with bedding

Vermicompost can be mixed directly into the soil, or leached in water and made into a worm tea by mixing some vermicompost in water and steeping for a number of hours or days.

The microbial activity of the compost is greater if it is aerated during this period. The resulting liquid is used as a fertilizer or sprayed on the plants.

The dark brown waste liquid, or leachate, draining into the bottom of some vermicomposting systems as water-rich foods break down, is best applied back to the bin when added moisture is needed due to the possibility of phytotoxin content and organic acids that may be toxic to plants.[8]

The pH, nutrient, and microbial content of these fertilizers varies upon the inputs fed to worms. Pulverized limestone, or calcium carbonate can be added to the system to basify the pH.

[edit] Problems

Worms and fruit fly eggs under the lid of a home worm bin.

When closed, a well-maintained bin is odorless; when opened, it should have a rich earthy smell like a forest floor[citation needed]. Bins must be oxygenatedTemplate:How. If decomposition becomes anaerobic from excess feedstock added to the bin in wet conditions; or layers of food waste have become too deep, the bin will begin to smell like ammonia.

In order to restore healthy conditions and prevent the worms from dying, the smelly, excess waste water must be removed and the bin returned to a normal moisture level. To do this, first reduce addition of food scraps with a high moisture content and second, add fresh, dry bedding such as shredded newspaper to your bin, mixing it in well.

Pests such as rodents and flies are attracted by certain materials and odors, usually from large amounts of kitchen waste, particularly meat. By eliminating the use of meat or dairy product in your worm bin you decrease the possibility of pests.

In warm weather, fruit and vinegar flies breed in the bins if fruit and vegetable waste is not thoroughly covered with bedding this problem can be avoided by maintaining the proper temperatureTemplate:How, to allow worms to continue eating the waste and allow the beneficial microbes to continue blooming[citation needed].

Commercial vermicomposters test, and may amend their products to produce consistent quality and results. The vermicompost produced by small-scale and home systems should occasionally be tested for nitrogen, potassium and phosphorus in order to avoid fertilization issues such as nitrogen burn.

[edit] Learning about vermicomposting

In the United States, state Cooperative Extension Services and local governments may provide assistance and training in home vermicomposting. In Canada many municipalities have education programs.

[edit] See also

[edit] References

[edit] External links

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