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Worm Composting

Worm composting (Vermicomposting) is a clean and odourless way to transform food waste into a rich fertilizer.

All you have to do is put some red wiggler worms (not local earth worms) into a bin with some moist bedding (see below). Then add your food scraps (like apple cores and vegetable peelings). The worms will eat the scraps and produce great compost for your house plants, garden or flowerbeds.

Do it indoors or out; it's perfect for apartment and house dwellers or at the office.

The worms work quickly at temperatures ranging from 15 to 25 degrees Celsius, consuming up to half their body weight in food each day.  They won't survive freezing temperatures, so they'll have to stay indoors during winter.

During the warmer months of the year, a working worm composter is on display at the John Janzen Composting Education Centre, located beside Fort Edmonton Park. There is an attendant at the centre to answer any questions you might have.

The Bin

Opaque plastic bins are ideal. They have lids, are moisture-proof, inexpensive and come in several sizes. Your container should be no more than 30 to 45 cm deep (12 - 18 inches) and have lots of air holes. Packing crates and foam plastic chests also work well.

The size of your bin depends on how much food you'll be adding. A bin should have about one square foot of surface area for each ½ kilogram (1 pound) of food added each week.

Worm Bin Plans

The Bedding

Proper bedding is important to maintain your worms' health. Shredded newspaper, potting soil (without chemicals), straw, fall leaves or a combination of these will be fine.

Fill your bin almost to the top with loose bedding then sprinkle water on it until it's as wet as a wrung out sponge. It should form a  mud ball when a handful is squeezed.

Feeding the Worms

Bury your scraps into a different part of the bedding each week to evenly distribute the food for the worms and to discourage flies. The smaller you cut the scraps, the faster they will disappear. The worms especially like lettuce, melons and apples, but you can feed them any vegetable scraps. Try to give them a variety and only a few citrus fruits to maintain the pH balance.

The chart below shows what works well, and what doesn't:

 Yum!  Yuck!
 Vegetable scraps  Meat
 Grains  Fish
 Fruit rinds and peels  Cheese
 Breads  Oily food
 Tea bags  Butter
 Coffee grounds  Animal products

Harvesting Worm Compost

After 3 to 6 months, the worms will have digested not just your food, but their bedding as well. What is left over is called vermicompost and it is an excellent additive to your house plants or flower beds.

There are several ways to harvest worm compost:

The Side-to-Side Method

1. Move finished compost to one side of the bin and fill the empty side with fresh bedding.

2. For the next six weeks or so bury food waste only in the newly bedded side of the bin.

3. The worms will eventually seek out the fresh food and migrate over to the new bedding and fresh food. When they have done so, you can scoop out the castings.

The Bright Light and Scoop Method

1. Shine a bright light on the worms. They will avoid the light and burrow down through the vermicompost.

2. Scoop off the top layer of vermicompost until you see the worms again.

3. Repeat the process. Eventually the worms will be concentrated at the bottom of the bin. These can be put into fresh bedding.

The Sun Dried Method

This is a fairly fast, easy way of harvesting the worms but it requires a second bin and some plastic mesh.

1. Put fresh moistened bedding in a second bin and cover the fresh bedding with 1/4" plastic mesh.

2. Dump the castings and worms from the first bin on top of the plastic mesh and put the new bin out in the sun.

3. The sun will dry the castings and the worms will move through the mesh into the moist bedding below.

4. The worm compost on top of the mesh is now ready for use.

Using Worm Compost

  • As potting soil - use 1 part worm compost to 5 parts potting soil.
  • As top dressing - sprinkle 1/4 inch of castings on houseplants, every 6 to 8 weeks.
  • As starter mix - sprinkle castings along bottom of seed row, or into the hole when you are transplanting.


Fruit Flies

One of the most common problems with bins are fruit flies.  Fortunately, they don't bite and they're easy to deal with.
  • Keep scraps covered with a few inches of bedding or castings.
  • Freeze scraps overnight before adding them to the bin.

Fungus Gnats

The other small flying insect which can invade your bin is more bothersome because it can also survive in your house plants.   An added challenge is that whatever you do to kill these pests may kill many of your beneficial decomposers.  Isolate your bin and harvest.

Other Creatures

Many other small creatures may share your bin with the worms. Most of them are helpful and rarely cause problems. Only centipedes, which will eat your worms, pose any threat to your bin.


If your bin smells bad, it probably has too much food, water, or the wrong types of food inside. To eliminate odours, remove excess or inappropriate food and add fresh bedding. You might also leave the lid off to allow for evaporation.

Where can I buy worms?

Dirt Willy Ecology & Bait Farm Ltd
53116 Range Road 210
Ardrossan AB  T8G 2E4
Phone: 780-983-4112

Earth's General Store
9605 - 82nd Avenue
Edmonton, AB T6C 0Z9
Phone: 780-439-8725

Red Wigglers Edmonton
Edmonton AB 
Phone: 780-668-6581

Vermiculture Canada
Site 8 Box 23 RR 2
Tofield AB  T0B 4J0
Phone: 780-662-3309
Toll free 1-866-225-5036

Get Help with your Compost Pile

Our staff and volunteers are ready to answer your questions or even visit your yard to help you compost better.

Title The Compost Doctors


Email compost@edmonton.ca
Facebook http://www.facebook.com/groups/96481566101/