Worm bins are designed for composting food wastes using red worms. Vegetable and fruit scraps from the kitchen are added on a regular basis; the worms eat the scraps and turn it into compost.
Build a worm bin
Worm bins make the most out of kitchen scraps.
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To set up a worm bin, you'll need:
- red worms
- a wide and shallow container
- fruit and vegetable scraps from your kitchen.
Fill the container three-quarters full with moistened bedding. Add the worms. Pull aside some of the bedding and put in some food scraps about once a week, and cover them up with bedding each time. In two to three months, the worms and microorganisms eat the original food waste and bedding and produce rich compost.
Red worms are recommended because they efficiently process food waste into compost. These worms will probably not survive in your garden.
You can purchase red worms from local or mail order suppliers or get some from a friend’s worm bin. Ask Metro for a list of retail suppliers.
The container should be between 8 and 16 inches deep, with holes drilled in the bottom and sides for aeration and drainage. You can build a wooden worm bin, or use a plastic tub with a lid.
Worm bins can handle about one pound (or one quart) of food scraps per week per square foot of bin surface area. This means a bin with a 1 by 2 foot floor will take about 2 quarts of food per week.
Worm bins need to help keep worms moist, dark and not too hot or cold. When temperatures drop below freezing, bins should be moved indoors or be well-insulated. They may be located outdoors, or in the basement, shed, garage, balcony or under the kitchen counter.
Building a worm bin?
Suitable bedding materials include:
- shredded newspaper or cardboard (not magazine pages)
- brown leaves
- coir (coconut fiber)
- untreated soft-wood sawdust or wood shavings
Setting up and maintaining
- Fill the bin three-quarters full with bedding that has been moistened so it is as wet as a wrung-out sponge.
- Add a handful of dirt, crushed eggshells or sand to provide necessary grit for the worms' digestion.
- During the course of several months, the worms will eat the bedding. Add more moistened bedding as necessary to maintain the bin at three-quarters full. There should always be about 4 inches of bedding over the worms and compost.
- When adding food waste to the bin, pull aside some of the bedding and bury the food. Bury successive loads in different locations in the bin.
Do feed your worms
- fruit and vegetable scraps (including citrus peels)
- coffee grounds and filters
- tea bags
Do not feed your worms
- meat, fish or dairy products
- greasy or oily foods
- breads, grains or dry beans
- pet waste (unless it is from a rabbit or chicken)
Harvest your worm compost
Harvest worm compost (AKA worm castings, vermicompost) from the bottom of the bin after several months or when it looks like soil. For small amounts, look for areas in the bin with soil-like compost and few worms and just grab handfuls. For larger quantities, you can push the contents of your bin to one side and fill the empty half with new bedding food and some of the active worm compost. Add all new food scraps to this new side for a few months. The worms should migrate over there, leaving pure compost on the side with the older material. Use the compost on your house plants, seedlings or for general garden use.