Learn how to make worm compost bins

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Master gardener Bonnie White demonstrates how to use worms to turn kitchen scraps into compost. Photo by: Judy Scott
Last Updated: 
August 12, 2009

ALBANY, Ore. – Worm composting is becoming more popular as people learn that their everyday table scraps can turn into rich, black compost within a few months with the help of small "red wigglers," also called composting worms.

Unlike night crawlers, which live in the ground and eat decomposing plants, composting worms live in their food, formerly your food, and their castings are full of microorganisms that enrich the soil.

"Red worms are smaller than earthworms and prefer to eat waste like rotting leaves, straw and fruit on the ground," according to Bonnie White, a master gardener with the Oregon State University Extension Service in Linn County. Red worms are best for composting fruit and vegetable scraps, and even coffee filters and other paper products, she said.

White teaches how to make worm or "vermicompost" bins from plastic (not clear) 10–14 gallon containers with lids to create a habitat for the worms that is damp and dark. Drill about 20 holes in both the bottom and top of the bin for aeration and drainage. Fill the bin half to three-quarters full with a combination of bedding materials such as shredded newspaper, office paper or cardboard; brown and dry leaves, straw, dryer lint, peat moss and/or sawdust.

Moisten the bedding so that it is as wet as a wrung-out sponge. Add a handful of dirt to provide grit that the worms need for digestion. Dry eggshells also work; run them through a blender and throw the resulting dust into the mix.

Then it's time to add red worms. Local or mail-order suppliers can be found on the Internet. Most suppliers sell composting worms by the pound. Sometimes you can find red worms for sale at farmers' markets, or check with friends and neighbors who garden and might be willing to share.

To feed the worms, White recommends pulling aside some of the bedding and "burying" the following: vegetable scraps, fruit peels and pulp (but not citrus, which can be too acidic), coffee grounds and filters, tea bags and foods such as old bread or crackers. Do not add meat, dairy products, greasy or oily foods; they can create odors and pest problems. Never add dog or cat wastes, which can carry disease.

Over time, more bedding will be needed as the worms consume it, White said. "Keep covering food you add to the bin with new moist bedding."

Place the bin on bricks or blocks for air circulation. Place the bin in an area that will not freeze in the winter and will not get hotter than 85 degrees in the summer. The bin can be kept outdoors in the shade, in the basement, cool shed or garage or under the kitchen counter in a dark cupboard. Place a tray underneath to catch moisture. Covering the bin provides darkness and prevents moisture loss.

After about six months, beautiful black vermicompost will be in a layer on the bottom of the bin. To remove compost without removing the worms, feed the worms on only one side of the bin a few weeks before removing the compost. The worms will move toward the food, vacating one side. Remove the compost from the empty side and add new moist bedding to the empty side.

White also recommends the "dump and sort method." Remove excess bedding and save. Then, dump composted matter from the bin on a tarp and shape it into small piles. In 10 to 15 minutes, the worms will burrow away from the light. You can lightly brush away the compost and separate it from the worms, which can be shared with others or used to start another bin. "Eight worms can produce about 1.5 pounds of worms every six months," White said.

Vermicompost, full of nutrients and beneficial microorganisms, can be used on houseplants, seedlings and in the garden. A small amount goes a long way.

Author: Judy Scott
Source: Bonnie White