Vermicompost (also called worm compost, vermicast, worm castings, worm humus or worm manure) is the end-product of the breakdown of organic matter by some species of earthworm. Vermicompost is a nutrient-rich, organic fertilizer and soil conditioner. The process of producing vermicompost is called "vermicomposting" .

The earthworm species (or composting worms) most often used are Red Wigglers ("Eisenia foetida") or Red Earthworms ("Lumbricus rubellus"). These species are commonly found in organic rich soils throughout Europe and North America and especially prefer the special conditions in rotting vegetation, compost and manure piles. Composting worms are available from nursery mail-order suppliers or angling (fishing) shops where they are sold as bait. Small-scale vermicomposting is well-suited to turn kitchen waste into high-quality soil, where space is limited.

Together with bacteria, earthworms are the major catalyst for decomposition in a healthy vermicomposting system, although other soil species also play a contributing role: these include insects, other worms and molds.


Vermicomposting bins (also known as worm bins) vary drastically depending on the desired size of the system. Garden-scale containers can be made out of bricks arranged in the shape of a box. Bins for an apartment or similar dwelling can be anything from reused plastic buckets to purpose-built commercial containers.

mall scale

Small-scale systems may use a wide variety of bins. Often, small-scale composters build their own bins. Companies also sell such bins. Commonly, bins are made of old plastic containers, wood, Styrofoam containers, or metal containers.

Some materials are less desirable than others in bin construction. Styrofoam is believed to release toxins into the earthworms' environment [cite web |url= |title=Compost Worms |accessdate=2008-02-12] . Metal containers often conduct heat too readily, are prone to rusting, and may release heavy metals into compost.

Bins should have holes in the sides to allow air to flow, and a spout that can be opened or closed or holes in the bottom to drain into a collection tray. Plastic bins require more drainage than wooden ones because they are non-absorbent. 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. Most small bins can be grouped into three categories:
*Non-continuous – an undivided container. A layer of bedding materials is placed in the bin, lining the bottom. Worms are added and organic matter for composting is added in a layer above the bedding. Another layer is added on top of the organic matter and the worms will start to compost the organic matter and bedding. This type of bin is often used because it is small and easy to build. But it is relatively difficult to harvest because all the materials and worms must be emptied out when harvesting.
*Continuous vertical flow – a series of trays stacked vertically. The bottom-most tray is filled first, in a similar fashion to any other bin, but is not harvested when it is full. Instead, a thick layer of bedding is added on top and the tray above is used for adding organic material. Worms finish composting the materials in the bottom tray and then migrate to the one above. When a sufficient number of worms have migrated, the vermicompost in the bottom tray can be collected and should be relatively free of worms. These bins provide an easier method of harvesting.
*Continuous horizontal flow – a series of trays lined horizontally. This method too relies on the earthworms migrating towards a food source in order to ease the process of harvesting. The bin is usually constructed to be similar to a non-continuous bin but longer horizontally. It is divided in half, usually by a large gauge screen of chicken wire. One half is used until it becomes full, then the other half is filled with bedding and organic matter. In time, the worms migrate to the side with the food and the compost can be collected. These bins are larger than a non-continuous system but still small enough to be convenient.

Large scale

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 (see bedding below) 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 killing the worm population. When large scale windrows are fed on one side consistently, a wave motion is generated over time.

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 and are 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. One major Australian company wormswork has successfully commissioned this continuous flow system at their manufacturing plant in Millicent South Australia. with the capacity of producing 12,000 tonnes of finished solid organic fertilizer and 6 million litres of organic liquid fertilizer annually. This can be seen at

tarting off

When beginning a vermicomposting bin, moist bedding is put into the bin and the worms are added. In hot climates, the bin is placed away from direct sunlight. Appropriate waste can be added daily or weekly. At first, the worms are fed at most half their body weight per day. After they have established themselves, they can be fed up to their entire body weight. It is best not to add new food on top of old food until the old food has been processed by the worms. However, new food can be added in a different location in the bin.


Bedding is the living medium and also a food source for the worms. It is material high in carbon and made to mimic decaying dried leaves on the forest floor, the worms' natural habitat. The bedding should be moist (often similar to the consistency of a wrung-out sponge) and loose to enable the worms to breathe and to facilitate aerobic decomposition of the food that is buried in it.

A wide variety of bedding materials can be used, including shredded newspaper, sawdust, hay, cardboard, coir, burlap coffee sacks, peat moss, pre-composted (aged) manure, and dried leaves. Cat litter, and pet and human waste should not be used.

Most vermicomposters avoid using glossy paper from newspapers and magazines, junk mail, and shredded paper from offices, because they may contain toxins which may disrupt the system. Also, coated cardboard that contains wax or plastic, such as milk boxes, cannot be used. Newspaper and phone books printed on regular, non-glossy paper with non-toxic soy ink are safe for use, and decompose relatively quickly. Some bedding is easier to use and add food scraps to than others.

Climate and Temperature

Worms used in composting systems prefer temperatures of 55 to 70 degrees Fahrenheit (12-21 degrees Celsius). The temperature of the bedding should not drop below freezing or above 89.6 °F (32 °C). This temperature range means that indoor vermicomposting is suitable for homes in all but tropical climates.

The [ map of vermicomposters location data] plots geographic data which shows which climates are suitable for worm composting.


Worms and other composting organisms have a preferred ratio of carbon to nitrogen (C:N), approximately 30:1. As some waste is richer in carbon and others in nitrogen, waste must be mixed to approximate the ideal ratio. "Brown matter", or wood products such as shredded papers, is rich in carbon. "Green matter", such as food scraps, has more nitrogen, which is related to the amount of protein in the waste. [cite web
title=C/N Ratio
coauthors=Nancy Trautmann
work=Cornell composting: composting in schools
publisher=Cornell university college of agriculture and life sciences
] If the waste is mostly vegetable and fruit scraps, and does not regularly include animal products or high-protein vegetable foods like beans, the resulting vermicompost and waste liquid will be low in nitrogen.


Kitchen waste suitable for worms includes coffee grounds and filters, tea bags and plate scrapings, as well as rotting fruit (including citrus fruit but NOT citrus peel), vegetable peels, leftovers, moldy bread, etc. These materials can be raw or cooked. They do not have to be ground up, as the micro-organisms in the bin will gradually soften them. However, if a large quantity of dry food (e.g., moldy bread) is added and covered with bedding, pour a little purified water over the bedding to moisten the mixture.

If too much kitchen waste is added, the bin mixture putrifies before the worms can process it and becomes harmful to the worms. High-protein foods like beans are particularly susceptible. Check the bin at least once a week, give the materials a stir to oxygenate, and add bedding if the bin appears too moist.

Soft garden wastes such as carrot tops and tomato leaves are suitable foods. An occasional sprinkling of garden soil in the bin gives the worms the grit they need to digest food. It's not harmful to throw in an entire plant, but the worms will not process the woody parts or large roots and these will have to be hand-removed later from the finished vermicompost.

Compostable plates, cups, etc. are also suitable, but in small bins they should be torn first into smaller pieces so as not to block oxygen flow.


High-water-content materials like watermelon rinds provide very little food for the worms while disrupting the moisture level of the system. They should be added sparingly.

Grass clippings and other products sprayed with pesticides should be avoided. Some banana peels are heavily sprayed, and can kill everything if added to a small bin.

Although worms can digest proteins and fats in meat scraps, these materials can attract scavengers. Too much oil or fat can hinder the breathing of the worms, as they breathe through their skin. Worms cannot break down bone and are said to dislike highly spiced foods such as onions, [ [ Fact Sheet: Building a Worm Farm] ABC Gardening Australia. Retrieved 2008-08-24] garlic, and salt.

If possible, sticky food labels, rubber bands, tea bag staples, and other inedibles should be removed before placing the food in the worm bin, as these items will not decompose. Fruit pits need not be removed from decaying fruit before adding, as the worms will eat all the soft matter.

Compostable cutlery takes too long to degrade in vermicompost.

Bin Maintenance

Worms and other composting microorganisms require oxygen, so the bin must "breathe". This can be accomplished by regularly removing the composted material, adding holes to the bin, or using a continuous-flow bin. If insufficient oxygen is available, the decay becomes anaerobic, like that in swamps and bogs, producing a strong odor and creating a toxic environment for the worms.

The moisture level and oxygen flow in a home worm bin should be checked at least once a week.

Over the long term, care should be taken to maintain optimum moisture levels. In a non-continuous-flow vermicomposting bin, excess liquid can be drained via a tap and used as plant food. A continuous flow bin does not retain excess liquid and, depending on the foods used, may require sprinklings of water to keep the bedding moist.

The pH should be slightly alkaline. Alkalinity can be increased by occasionally adding a handful of calcium carbonate, sold as "garden lime." Do not confuse calcium carbonate with regular lime (Calcium oxide), which is far too alkaline and will kill worms. Adding many citrus peels can hinder the worms, but probably due not to acidity but to d-limonene, a fragrant chemical present in the rind of citrus fruits. [In her book, [ "Worms Eat My Garbage"] , (Kalamazoo, MI: Flower Press, 1997), p. 64, pioneering vermicomposter Mary Appelhof says that another science teacher's ninth-grade student did a science project that identified limonene as the toxin. Appelhof was skeptical but realized that the student probably had a parent who worked at a nearby Dupont Chemical Company research facility with the ability to do the tests.] Coffee grounds have sometimes been blamed for acidity, but analysis shows they are only mildly acidic, with a pH of 6.2. [cite web
title=The Starbucks coffee compost test
author=Soil and Plant Laboratory Inc., Bellevue, WA.
work=Sunset magazine


There are two methods of adding matter to the bin.
*Top feeding — organic matter is placed directly on top of the existing layer of bedding in a bin and then covered with another layer of bedding. This is repeated every time the bin is fed.
*Pocket feeding — a top layer of bedding is maintained and food is buried beneath. The location of the food is changed each time, rotating around the bin to give the worms time to decompose the food in the previously fed pockets. The top layer of bedding is replenished as necessary.

Vermicomposters often use a combination of both methods. Sometimes unburied food can attract fruit flies, so food should be buried under at least one inch of bedding material.


Vermicompost is ready for harvest when it contains few to no scraps of uneaten food or bedding. Even a properly composted mixture will contain large items that should be discarded, such as peach or date pits, glassine-like sheets from melon skins, and twigs. Small seeds from composted food such as tomatoes and apples cannot be removed from the vermicompost and may sprout later in the seed-starting pots or garden.

There are several methods of harvesting, 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.

Vermicompost properties

Vermicompost, also known as worm castings and vermicast, is richer in many nutrients than compost produced by other composting methods. It is also rich in microbial life which helps break down nutrients already present in the soil into plant-available forms. Unlike other compost, worm castings also contain worm mucus which keeps nutrients from washing away with the first watering and holds moisture better than plain soil. For this reason,some fruit and seed pits are reported to germinate in vermicompost easily. Vermicompost made from ordinary kitchen scraps will contain small seeds, especially those of tomatoes, peppers, and eggplants, that may sprout weeks later.

Vermicompost benefits soil by
*improving its physical structure;
*enriching soil in micro-organisms, adding plant hormones such as auxins and gibberellic acid, and adding enzymes such as phosphatase and cellulase;
*attracting deep-burrowing earthworms already present in the soil;
*improving water holding capacity;
*enhancing germination, plant growth, and crop yield; and
*improving root growth and structure.

Vermicompost can be used to make compost tea (worm tea), by mixing some vermicompost in water and steeping for a number of hours or days. The resulting liquid is used as a fertilizer.

The dark brown waste liquid that drains into the bottom of some vermicomposting systems, as water-rich foods break down, is also excellent as fertilizer. However, the pH and nutrient contents of these liquids (as well as vermicompost) varies, depending on the food fed to the worms and whether or not lime has been added to the system. pH and nitrogen, phosphorus, and potassium (NPK) measurements should be taken periodically to determine the fertilizer composition before use. Home kits for testing are sold in hardware stores and nurseries.


Odor, usually due to overabundance of "greens" (wet waste) in the bin, results from too much nitrogen combining with hydrogen to form ammonia. To neutralize the odors, add a fair amount of shredded newspaper or other "browns" to the mix to absorb excess moisture, remove the smelly waste, and stop adding food to the bin until a substantial portion of the uneaten food has been turned into compost. The carbon will balance the nitrogen and form a compound that is not smelly. The higher level of carbon means that decomposition will be slower. Also, always add new material deep in the bin to disallow access to would-be pests. Consistently doing so will greatly reduce any nuisance from odor and undesirable organisms.

Pests such as rodents and flies may be attracted by certain materials and odors, especially lots of kitchen waste and especially meat. This problem is largely avoided if a sealed bin is used where the pests cannot access the material, although many proponents recommend having ample access to air. This promotes natural decomposition, as worms and beneficial bacteria require oxygen. Fruit flies are common in warm weather if the food is not thoroughly covered with bedding.

Commercially available vermicomposting systems

Home vermicompost systems or worm bins are available from many retailers. Clive Roberts BSc invented the very first 'Wormery' in the late 1980s and in 1991 patented his design for The Original Wormery, in the UK.

In the United States, state Cooperative Extension Services and local governments may provide assistance and training in home vermicomposting.

ee also



External links

* [ with map] by Steven Chow.

Wikimedia Foundation. 2010.

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