Horticulture/Vermicomposting/transwiki

This is the [wikipedia article] as copied on March 2, 2006.

Vermicompost (or Worm Compost) is the name for the castings produced from the breakdown of organic matter by special varieties of earthworms. Compared to ordinary soil, the earthworm castings (the material produced from the digestive tracts of worms) contain five times more nitrogen, seven times more phosphorus and 11 times more potassium. They are rich in humic acids and improve the structure of the soil.

The earthworm most often to be found in the compost heap is Brandling Worms (Eisenia foetida), or Redworms (Lumbricus rubellus). This species is only rarely found in soil and is adapted to the special conditions in rotting vegetation, compost and manure piles. Earthworms are available from mail-order suppliers, or from angling shops where they are sold as bait. Small scale vermicomposting is well suited to turn kitchen wastes into high quality soil where space is limited.

In addition to worms, a healthy vermicomposting system hosts many other organisms such as insects, molds, and bacteria. Though these all play a role in the composting process, the earthworm is the major catalyst for the composting process.

Bins

Vermicomposting bins vary drastically depending on the system an individual composter wishes to create.

Small scale

Small scale systems offer a wide variety of bins. Often, small-scale composters build their own bins. Companies also offer commercial models for sale. Commonly, bins are built out 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. Metal containers often conduct heat too readily, are prone to rusting, and may release heavy metals into compost.

The design of small bins usually depends on where an individual wishes to store the bin and how they wish to feed the worms. All bins in general have holes for airflow in the sides and some form of drainage, either holes in the bottom to drain on to a collection tray or an actual spout that can be opened or closed to allow drainage. Plastic bins in general require more drainage than wooden because they are non absorbent. Regardless of the material used to build the bin, most small bins can be grouped into three categories:

Non-Continuous – A non-continuous bin is an undivided container. A layer of bedding materials is placed in the bin lining the bottom and 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. These type of bins are often used because they are small in size and easy to build. They are relatively difficult to harvest because all the materials and worms must be emptied out when harvesting.
Continuous Vertical Flow – Continuous flow bins are 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. The idea is that the worms will finish composting the bottom tray and then migrate to the one above. When a sufficient number of worms have migrated 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 continuous horizontal flow bin is another a bin that relies on the earthworms habits of 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 twice as long (horizontally). The bin is divided in half, usually by a large gauge screen of chicken wire. Only one side is used initially. When that half becomes full, the other half is filled with bedding and organic matter. In time, the worms will migrate to the side with the food and the compost can be collected. These bins are larger than a non-continuous system but are still small enough to be used indoors, with the added bonus of being easier to harvest.

Large scale

Most large scale vermicomposting or vermiculturing systems do not incorporate an actual physical bin at all, because it is simply too impracticable. A large system will usually use a windrow. The windrow simply consists of bedding materials for the earthworms to live in (see bedding below) and acts as a large worm bin; organic material is added to the windrow and the worms perform the composting. 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 times windrows are used on a concrete surface to prevent predators from killing off worm populations.

Starting Off

When beginning a vermicomposting bin, add as many composting worms as available. They should be added to moist bedding. Quantities of kitchen waste appropriate for the worm population can be added to the bin daily or weekly. At first, feed the worms approximately 1/2 their body weight in kitchen scraps a day, maximum. After they have established themselves, you can feed them up to their entire body weight.

Bedding

Bedding in a worm bin is the living medium for the worms but is also used as a food source, it is material that is high in carbon and is made to mimic dried leaves on the forest floor, which is the worms' natural habitat. The bedding needs to be moist (often related to the consistency of a wrung-out sponge) and loose to enable the earthworms to breath and to facilitate aerobic decomposition. A wide variety of bedding materials can be used including newspaper, sawdust, hay, cardboard, peat moss, aged manure (meaning the manure has to be pre-composted before use), and dried leaves. Most vermicomposters avoid using any glossy papers from newspapers and magazines, junk mail and shredded paper from offices, because they may contain toxins which will severely affect the system. Also some cardboard cannot be used if it contains wax or plastic, such as cereal boxes, and other boxes designed to hold food items. Newspapers and phone books printed on regular, non-glossy pages are heavily regulated by the FDA and use non-toxic soy and Canola based inks (see Soy ink).

Temperature

The worms that are used in composting systems prefer temperatures between 55 and 70 degrees Fahrenheit (c. 12-21 degrees Celsius), and temperature of the bedding should not get below freezing or above 85 degrees Fahrenheit (29 degrees Celsius).

Kitchen waste

Greens - If too much kitchen waste is added for the worms to process, the waste will putrify. A balance between "green matter" such as kitchen scraps and "brown matter" such as shredded newspaper for bedding must be maintained in order for the worms to do their work. This balance should be approximately one part "green matter" for every two parts of "brown matter". Covering the kitchen scraps with a layer of "brown matter" also has the added benefit of reducing odor and insect problems. Avoid grass clippings or other plant products that have been sprayed with pesticides. In a small bin, this includes banana peels which can kill everything in the bin, if heavily sprayed.

Meats - Although proteins such as fats and meat scraps can be processed by a vermicompost bin, doing so tends to attract scavengers and should be avoided if this is a risk. Worms are unable to break down bone or synthetic material.

Fecal Matter - Fecal material of omnivores and carnivores is unsuitable for composting due to the dangerous microorganisms it contains, though thermophilic composting or other applied heat can mitigate this problem. People have reported successfully using cow, rabbit, or goat manure to help start up the bin. If done, this should be used in small quantities. If you are vermicomposting inside your home, you may want to avoid including manure or dairy products in your compost because they may have an unpleasant odor.

Over the long term, care should be taken to maintain optimum moisture levels and pH balance. In a non-continuous-flow vermicomposting bin, excess liquid can be drained via a tap and used as plant food. A continuous flow bin will not retain excess liquid and it requires extra water to be added to keep the bedding moist. Too many citrus peels in the material to be composted can cause excessive acidity, but this can be mitigated by adding an occasional handful of lime.

Worms as well as other microorganisms in the composting process require oxygen, so the bin must "breathe". This can be accomplished by regularly removing the composted material, adding holes to a composting bin, or using a continuous-flow bin. If insufficient oxygen is available, the compost will become anaerobic. This will provide a host environment for a different type of decay process which produces a strong odor offensive to most people. This type of decay is found in swamps and bogs and is responsible for the stench sometimes found in these environments.

Feeding methods

There are basically two methods of adding more matter to the bin.

The first method, known as top feeding, is when organic matter placed directly on top of the existing layer bedding in a bin and then covered with another layer of bedding. This is repeated every time the bin is fed.
The other method of feeding is known as pocket feeding. In this method a top layer of bedding is maintained and food is buried beneath. The location of the food is changed each time and often the bin is fed in more than one location. As bedding runs low more is added. Vermicomposters often use a combination of both methods. Sometimes by not burying the food it can attract w:fruit flies.

Problems

Odors - When this occurs it is usually due to the overabundance of "greens" in the bin, which is actually too much nitrogen combining with hydrogen and forms the ammonia. To neutralize the odors you want to add a fair amount of carbon to the mix. The carbon will instead absorb the nitrogen and form a compound that is not smelly. Paper and dried leaves are good sources of carbon. Take note; too much carbon added slows the decomposition process considerably.

Pests - certain types of material, as well as odours from these, can attract pests such as rodents and flies. This is especially true if the loading contains lots of kitchen waste, especially meat. This problem is largely negated if a sealed bin is used where the pests cannot access the material. Most domestic vermicomposters are advised by local authorities to avoid the problem of pests by avoiding using materials that attract them rather than relying on special containers.

Note: Red Wiggler worms are not native to North America. They are an invasive species and have become naturalized in most of the globe. Do not dump worm-containing compost in natural areas as they can have the effect of displacing the native worms.

Vermicompost properties

Worm compost is usually too rich for use as a seed compost, but is useful as a top layer of soil or an addition to potting composts. Some types of pitted seeds are reportedly easier to germinate when placed in vermicompost for several months.

Vermicompost is beneficial for soil in three ways:

It improves the physical structure of the soil.
It improves the biological properties of the soil (enrichment of micro-organisms, addition of growth hormones such as auxins and gibberellic acid, and addition of enzymes, such as phosphates, cellulase, etc.).
It attracts deep-burrowing earthworms already present in the soil.

External links

Worm Digest - includes articles on vermicomposting, links to suppliers and a discussion board
Worms Eat My Garbage (ISBN 0942256107), by Mary Appelhof. A "how-to" book on starting and maintaining a vermicomposting bin.
TheGardenForums.org: composting and vermicomposting community and forums
GardenWeb: vermicomposting forum - For discussions of vermicomposting and vermiculture
Klickitat County Site - Contains plans for Continuous Vertical Flow Worm Bin - See OSCR JR. links on this page