Worm Composting
Let Worms Eat Your Kitchen Waste
Another method of composting, separate from the backyard bin or compost pile method, is known as vermicomposting, a.k.a., worm composting. This is the practice of using worms to do your composting. Worms are macroorganisms that feed on your fruit and vegetable trimmings, and decompose them for you. The goal of vermicomposting is to create the ideal environment for worms to thrive so they can efficiently decompose the material you feed them. Worm composting is simple. You need a box, bedding, fruit and vegetable trimmings, and worms.
The Box
You can either buy a worm box or make your own. A plastic storage box purchased from a local retailer can serve as a great worm bin. A homemade worm box should be a sturdy wooden box with a tight-fitting lid. It can be made from scrap wood or constructed with plywood and two-by-fours. A tight-fitting lid keeps pests out and protects the worms. (The worms will not escape from their box. They are not attracted to light; hence, they migrate toward the center of their box.) It is best to drill ¼-inch holes in the bottom of the box to allow for drainage.
The box should be sized to provide one square foot of surface area for each person in the household. For example, a 2' x 2' x 2' box will handle the food waste of a four-person household.
The Bedding
Common bedding materials include shredded newspaper, corrugated cardboard, coarse peat moss, and partially decomposed leaves. Worm boxes should be filled with bedding to provide the worms with a balanced diet as well as a damp, aerated place to live.
Tear newspaper or cardboard into one-to-two-inch strips before using as bedding. Bedding material should be thoroughly moistened by soaking it in water for several minutes. Squeeze out the excess water before adding bedding material to the worm box.
Always cover food waste with a few inches of bedding to prevent flies from becoming a problem. Rotate the location where food is buried in order to provide the worms with a balanced diet of kitchen scraps and bedding.
The Worms
Red worms,< known as red wigglers or manure worms, are the best for vermicomposting. They thrive on organic material such as fruit and vegetable trimmings. Red worms are not the same as earthworms or night crawlers, which need mineral soil to survive.
One to two pounds of worms are needed to start a worm box. Worms regulate their own population based on how much food is available. In other words, if they have a lot to eat, they increase their population. If food is scarce, their population decreases until the food supply increases. Worms reproduce very quickly. It is estimated that eight worms can multiply to 1,500 worms in six months. Once your system is established, there will be plenty of worms to help your friends get worm bins started.
Red wigglers are available through UC Davis Project Compost (754-8227).
Feeding the worms
Worms will eat fruit and vegetable peelings, coffee grounds, tea bags, crushed eggshells, rice, and leftovers. Most people prefer to raise “vegetarian” worms to avoid odors from decaying meat scraps. Be sure to bury your food scraps in the bedding to discourage molds and fruit flies. Bury the food in a different corner of the box at each feeding. The next time you look, it should be gone. If not, try feeding your worms a little less for a while.
| DO feed the worms | Do NOT feed the worms |
| fruits and vegetables bread, rice, pasta coffee grounds and filters small bits of plant material tea leaves with bags crushed eggshells |
meat, dairy, bones, fish greasy foods peanut butter pet/animal litter/feces salad dressing vegetable oil |
The Harvest
Harvesting worm compost is very easy. Simply feed one end of the box for a week or more. The majority of the worms will migrate to that side of the box. Scoop out two-thirds of the worm castings from the opposite end and put fresh bedding in its place. Start burying food waste in the new bedding, and the worms will migrate back.
Trouble Shooting Guide for Worm Composting
| Symptoms | Problems | Solution |
| Worm Bin smells bad | • Too much food | • Feed less |
| • Too Wet | • Check drainage holes/add dry bedding. | |
| Fruit Flies | • Food isn’t buried | • Bury food • Cover surface of bedding w/carpet or a sheet of newspaper |
| Worms aren’t eating | • Too much food | • Feed less |
| • Too acidic | • Stop feeding citrus peelings • Sprinkle w/crushed oyster shells |
More Information
More information about worm composting can be found on the California Integrated Waste Management Board (CIWMB) web site www.ciwmb.ca.gov/Organics/Worms.
Copies of Mary Appelhof's book Worms Eat My Garbage (1982) are available for loan at the Davis branch of the Yolo County Public Library, 315 East 14th Street, 757-5591.
Worms and worm composting classes are available through UC Davis Project Compost (754-8227).