Earthworm casting | Wikipedia audio article

Vermicompost (vermi-compost, vermiculture)
is the product of the composting 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. Vermicast (also called worm castings, worm
humus, worm manure, or worm feces) is the end-product of the breakdown of organic matter
by earthworms. These castings 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 and is an excellent,
nutrient-rich organic fertilizer and soil conditioner. It is used in farming and small scale 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 composting, it also generates products
that have lower salinity levels. The earthworm species (or composting worms)
most often used are red wigglers (Eisenia fetida or Eisenia andrei), though European
nightcrawlers (Eisenia hortensis or Dendrobaena veneta) 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.==Design considerations=====
Suitable worm species===One of the species most often used for composting
is the red wiggler or tiger worm (Eisenia fetida or Eisenia andrei); Lumbricus rubellus
(a.k.a. red earthworm or dilong (China)) is another breed of worm that can be used, but
it does not adapt as well to the shallow compost bin as does Eisenia fetida. European nightcrawlers (Eisenia hortensis)
may also be used. Users refer to European nightcrawlers by a
variety of other names, including dendrobaenas, dendras, and nightcrawlers. African Nightcrawlers (Eudrilus eugeniae)
are another set of popular composters. Lumbricus terrestris (a.k.a. Canadian nightcrawlers
(US) or common earthworm (UK)) are not recommended, since they burrow deeper than most compost
bins can accommodate.Blueworms (Perionyx excavatus) may be used in the tropics.These species commonly
are found in organic-rich soils throughout Europe and North America and live in rotting
vegetation, compost, and manure piles. They may be an invasive species in some areas. 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 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.===Large scale===
Large-scale vermicomposting is practiced in Canada, Italy, Japan, India, Malaysia, the
Philippines, and the United States. 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. The windrow method and compost 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. 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.===Small scale===For vermicomposting at home, 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. Metal containers often conduct heat too readily,
are prone to rusting, and may release heavy metals into the vermicompost. Styrofoam containers may release chemicals
into the organic material. Some cedars, Yellow cedar, and Redwood contain
resinous oils that may harm worms, although Western Red Cedar has excellent longevity
in composting conditions. Hemlock is another inexpensive and fairly
rot-resistant wood species that may be used to build worm bins.Bins need holes or mesh
for aeration. Some people add a spout or holes in the bottom
for excess liquid to drain into a tray for collection. The most common materials used are plastic:
recycled polyethylene and polypropylene and wood. Worm compost bins made from 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 (turning the bin) that bin composting requires. Composting worms which are detritivorous (eaters
of trash), such as the red wiggler Eisenia fetidae, are epigeic (surface dwellers) and
together with symbiotic associated microbes are the ideal vectors for decomposing food
waste. Common earthworms such as Lumbricus terrestris
are anecic (deep burrowing) species and hence unsuitable for use in a closed system. Other soil species that contribute include
insects, other worms and molds.===Climate and temperature===
There may be differences in vermicomposting method depending on the climate. It is necessary to monitor the temperatures
of large-scale bin systems (which can have high heat-retentive properties), as the raw
materials or feedstocks used can compost, heating up the worm bins as they decay and
killing the worms. The most common worms used in composting systems,
redworms (Eisenia foetida, Eisenia andrei, and Lumbricus rubellus) feed most rapidly
at temperatures of 15–25 °C (59-77 °F). They can survive at 10 °C (50 °F). Temperatures above 30 °C (86 °F) may harm
them. This temperature range means that indoor vermicomposting
with redworms is possible in all but tropical climates. Other worms like Perionyx excavatus are suitable
for warmer 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.==Feedstock==
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.===Small-scale or home systems===
Such systems usually use kitchen and garden waste, using “earthworms and other microorganisms
to digest organic wastes, such as kitchen scraps”. This includes: All fruits and vegetables (including citrus,
in limited quantities) Vegetable and fruit peels and ends
Coffee grounds and filters Tea bags (even those with high tannin levels)
Grains such as bread, cracker and cereal (including moldy and stale)
Eggshells (rinsed off) Leaves and grass clippings (not sprayed with
pesticides) Newspapers (most inks used in newspapers are
not toxic) Paper toweling (which has not been used with
cleaners or chemicals)===Large-scale or commercial===
Such vermicomposting systems need reliable sources of large quantities of food. Systems presently operating use: Dairy cow or pig manure Sewage sludge
Brewery waste Cotton mill waste
Agricultural waste Food processing and grocery waste
Cafeteria waste Grass clippings and wood chips==Harvesting==Vermicompost is ready for harvest when it
contains few-to-no scraps of uneaten food or bedding. There are several methods of harvesting from
small-scale systems: “dump and hand sort”, “let the worms do the sorting”, “alternate
containers” and “divide and dump.” These differ on the amount of time and labor
involved and whether the vermicomposter wants to save as many worms as possible from being
trapped in the harvested compost. The pyramid method of harvesting worm compost
is commonly used in small-scale vermiculture, and is considered the simplest method for
single layer bins. In this process, compost is separated into
large clumps, which is placed back into composting for further breakdown, and lighter compost,
with which the rest of the process continues. This lighter mix is placed into small piles
on a tarp under the sunlight. The worms instinctively burrow to the bottom
of the pile. After a few minutes, the top of the pyramid
is removed repeatedly, until the worms are again visible. This repeats until the mound is composed mostly
of worms. While harvesting, it’s also a good idea to
try to pick out as many eggs/cocoons as possible and return them to the bin. Cocoons are small, lemon-shaped yellowish
objects that can usually be seen pretty easily with the naked eye and picked out. The cocoons can hold up to 20 worms (though
2-3 is most common). Cocoons can lay dormant for as long as two
years if conditions are not conducive for hatching.==Properties==
Vermicompost has been shown to be richer in many nutrients than compost produced by other
composting methods. It has also outperformed a commercial plant
medium with nutrients added, but levels of magnesium required adjustment, as did pH.However,
in one study it has been found that homemade backyard vermicompost was lower in microbial
biomass, soil microbial activity, and yield of a species of ryegrass than municipal compost.It
is rich in microbial life 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.Increases in the total nitrogen content in vermicompost,
an increase in available nitrogen and phosphorus, as well as the increased removal of heavy
metals from sludge and soil have been reported. The reduction in the bioavailability of heavy
metals has been observed in a number of studies.==Benefits==
Soil Improves soil aeration
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 Attracts deep-burrowing earthworms already
present in the soil Improves water holding capacityPlant growth Enhances germination, plant growth, and crop
yield Improves root growth and structure
Enriches soil with micro-organisms (adding plant hormones such as auxins and gibberellic
acid)Economic Biowastes conversion reduces waste flow to
landfills Elimination of biowastes from the waste stream
reduces contamination 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 regionsEnvironmental Helps to close the “metabolic gap” through
recycling waste on-site Large systems often use temperature control
and mechanized harvesting, however other equipment is relatively simple and does not wear out
quickly Production reduces greenhouse gas emissions
such as methane and nitric oxide (produced in landfills or incinerators when not composted).==Uses=====Soil conditioner===
Vermicompost can be mixed directly into the soil, or mixed with water to make a liquid
fertilizer known as worm tea. The dark brown waste liquid, or leachate,
that drains into the bottom of some vermicomposting systems is not to be confused with worm tea.It
is an uncomposted byproduct from when water-rich foods break down and may contain pathogens
and toxins. It is best discarded or applied back to the
bin when added moisture is needed for further processing.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 raise the pH.==Operation and maintenance=====Smells===
When closed, a well-maintained bin is odorless; when opened, it should have little smell—if
any smell is present, it is earthy. The smell may also depend on the type of composted
material added to the bin. An unhealthy worm bin may smell, potentially
due to low oxygen conditions. Worms require gaseous oxygen. Oxygen can be provided by airholes in the
bin, occasional stirring of bin contents, and removal of some bin contents if they become
too deep or too wet. If decomposition becomes anaerobic from excess
wet feedstock added to the bin, or the layers of food waste have become too deep, the bin
will begin to smell of ammonia.===Moisture===
Moisture must be maintained above 50%, as lower moisture content will not support worm
respiration and can increase worm mortality. Operating moisture-content range should be
between 70-90%, with a suggested content of 70-80% for vermicomposting-oriented vermiculture
operations. If decomposition has become anaerobic, to
restore healthy conditions and prevent the worms from dying, excess waste water must
be reduced 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.===Pest species===
Pests such as rodents and flies are attracted by certain materials and odors, usually from
large amounts of kitchen waste, particularly meat. Eliminating the use of meat or dairy product
in a worm bin decreases the possibility of pests.Predatory ants can be a problem in African
countries.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 thoroughly
covering the waste by at least 5 centimetres (2.0 in) of bedding. Maintaining the correct pH (close to neutral)
and water content of the bin (just enough water where squeezed bedding drips a couple
of drops) can help avoid these pests as well.===Worms escaping===
Worms generally stay in the bin, but may try to leave the bin when first introduced, or
often after a rainstorm when outside humidity is high. Maintaining adequate conditions in the worm
bin and putting a light over the bin when first introducing worms should eliminate this
problem.===Nutrient levels===
Commercial vermicomposters test, and may amend their products to produce consistent quality
and results. Because the small-scale and home systems use
a varied mix of feedstocks, the nitrogen, potassium and phosphorus content of the resulting
vermicompost will also be inconsistent. NPK testing may be helpful before the vermicompost
or tea is applied to the garden. In order to avoid over-fertilization issues,
such as nitrogen burn, vermicompost can be diluted as a tea 50:50 with water, or as a
solid can be mixed in 50:50 with potting soil.Additionally, the mucous layer created by worms which surrounds
their castings allows for a “time release” effect, meaning not all nutrients are released
at once. This also reduces the risk of burning the
plants, as is common with the use and overuse of commercial fertilizers.==Application examples==
Vermicomposting (also known as vermiculture) is widely used in North America for on-site
institutional processing of food scraps, such as in hospitals, universities, shopping malls,
and correctional facilities. Vermicomposting is used for medium-scale on-site
institutional organic material recycling, such as for food scraps from universities
and shopping malls. It is selected either as a more environmentally
friendly choice than conventional disposal, or to reduce the cost of commercial waste
removal. Researchers from the Pondicherry University
discovered that worm composts can also be used to clean up heavy metals. The researchers found substantial reductions
in heavy metals when the worms were released into the garbage and they are effective at
removing lead, zinc, cadmium, copper and manganese.==See also==Fertilizer
Home composting Maggot farming
Mary Arlene Appelhof Vermifilter
Vermiponics, use of wormbin leachate in hydroponics Waste management

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