(Compiled by George Bushell based on City of Toronto information)
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
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
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.
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.
- 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.
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.
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.
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.
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.