Build a compost worm bin

Enrich soil and recycle waste

By Judy Scott

Table scraps plus wiggly worms equal vermicompost. Photo by Michael Noack and Sally Noack

Although compost worm bins and their "red wiggly" worms are known for their ability to turn worm castings into rich compost, in the process they also recycle food waste otherwise destined for the landfill.

A new 13-page booklet by the Oregon State University Extension Service gives detailed instructions on how to compost with worms in a process called "vermicomposting." Written by Sam Angima, an OSU Extension agriculture faculty member, and OSU Master Gardeners Michael and Sally Noack, the guide also tells how to make a vermicompost bin.

Composting with Worms, EM 9034, is online and is free of charge.

"Food waste makes up about 20 percent (by weight) of landfill materials," Angima said. "When the food decomposes, it makes methane, a greenhouse gas about 20 times more potent than carbon monoxide as a gas that warms the atmosphere."

Vermicomposting is an easy process compared to conventional composting methods, which need complex ratios of materials and to be turned frequently, Angima said. "Worm compost bins are ideal for people who don't have a place for a regular compost bin, and the bins keep well indoors without odor if well-tended."

What do you feed a "wiggly worm?" These worms have amazing powers of digestion and will consume just about any organic matter such as fruit and vegetable scraps, pulverized eggshells and coffee grounds, Angima said.

"Earthworms, however, will not survive in the environment of an indoor worm bin," Angima said.

After three to six months, the mixture of worm castings and decomposed organic matter looks like crumbly chocolate cake and smells earthy and fresh, Angima said. You can use it blended with potting or garden soil or as fertilizer and soil amendment for house plants. Vermicompost adds beneficial bacteria, fungi and protozoa to the soil, as well as nitrogen, phosphorus, potassium, calcium and magnesium.

The OSU booklet illustrates how to build a bin and add bedding and where to buy worms. Most homemade worm bins are refurbished plastic totes, but wooden bins and commercial stackable towers also are popular.

"Worms are very sensitive to light; be sure if you use a plastic container that it's opaque, has a lid and is well-vented, as worms need oxygen to survive," Angima said.