Vermicomposting, or worm composting, is the decomposing of organic waste with red worms. It is a very convenient way of composting for apartment dwellers, school staff and students, persons with disabilities, office workers, elderly persons and anyone else who would have difficulty maintaining an outdoor compost pile. Vermicomposting creates a fine black granular compost called “castings”. Worm castings are an excellent source of slow-release soil nutrients for your plants or lawn. They also act as an excellent soil additive that prevents the caking of soil in potted plants.
Creating a Home for Your Worms
Bedding – Red worms can live in bins made from plastic or wood. These containers are partially filled with bedding material, most commonly peat moss, shredded newspaper, shredded cardboard, straw or a combination of these materials.
Moisture – The worm bedding should be kept as moist as a well-wrung sponge. Occasionally, the bedding can become too wet and needs to be gently loosened with a hand cultivator or small garden fork.
Acidity – Redworms prefer a bedding that it slightly acidic. However, if the bedding is all peat moss, or the materials added are very acidic, add crushed and dried egg shells to reduce the acidity.
Light – Red worms are very sensitive to light and need an opaque bin that has a lid or a dark plastic bag placed over the bedding to keep out the light.
Ventilation – Most bins also have some means of ventilation, either through holes drilled in the bin itself or a system of air tubing that runs through the bin from one side to another. Additional dry bedding material can also be added to help keep air in the bedding.
Drainage – Worm bins with holes in the bottom for drainage should be placed on one by two inch blocks on a plastic tray. The tray will collect any liquid which may drain from the bin. A piece of sheer fabric should be laid over the drainage holes to prevent the worms from falling through.
Choosing the Size of Your Bin
You should keep in mind that red worms eat their own weight in food every day. In other words, if you produce two pounds of food waste everyday, then you should have two pounds of worms in your bin. If you find that your red worms are being overfed, simply get another bin and a few more worms.
Finding Your Worms
Redworms are available for purchase from commercial growers, but can also be found for free in your own backyard! They are small, under four inches in length, and red, with alternating dark and light brown stripes. Redworms live in organic matter which is in contact with the ground. You will find them in decomposing leaves and decaying plant waste, manure, and the cooler decomposed parts of a compost pile. They generally live within the top four inches of soil, thus they are called the “surface feeders” of the earthworm family.
Note: Redworms are not the worms that appear on roads and sidewalks after a rainfall.
Feeding Your Worms
Red worms, a.k.a. red wrigglers, trout worms, manure worms or tiger worms, eat almost everything that humans eat. Worms should be fed at least every few days. Simply bury the food scraps a minimum of one inch below the surface of the bedding and leave for the worms to eat. Fresh food waste decomposes in about a week or two.
Harvesting the Bin
Every three to six months the red worms will have converted the food wastes and their bedding into a mass of rich dark castings. When the volume of the bedding has decreased, becomes noticeably darker, and you begin to see individual castings, it is then time to change or “harvest” the bedding. Worms do not survive in their own waste and must have it removed.
Methods of Harvesting
Layering: Expose the contents of the bin to light. This will cause the worms to work their way down towards the bottom of the bin, as they will try to avoid the light. As they move downward, remove one layer of compost at a time. The last layer will be mostly worms. Add new bedding and the vermicomposting process will start again.
Sorting: Prepare half the original quantity of fresh bedding. Pull the contents of the bin to one side and add the new bedding to the cleared side. Bury the food waste in the new bedding and let the worms find their way to it. After one to two weeks, check to make sure most of the worms have moved to the new bedding. Pick out any remaining worms. Then remove the old bedding. Repeat this process, when necessary, alternating each half of the bin for new bedding.
Removal for Gardening: Remove about two-thirds of the contents of the bin, and use the compost, complete with worms, directly on your garden during the gardening season. Fresh bedding can then be placed in the bin, as there should be enough worms and cocoons to populate the new bedding. Make sure that you do not overfeed the worms at this time.
Pile and Sort: Dump the contents of the bin onto a large plastic sheet and separate into small cone-shaped piles. Place a bright light above the sheet. The worms will move down away from the light and you can then remove the compost from the top of each pile. A small pile of worms will remain, which can then be weighed. Add fresh bedding and replace the correct amount of worms. The remainder can be used to start another bin for you or someone else.