Vermicomposting utilizes the impressive appetites of earthworms to produce compost in confined spaces. Red wiggler earthworms (Eisenia fetida) can eat their weight in garbage every day, and their digestive systems act as miniature composting units, converting that garbage into castings rich in nutrients and organic matter. Furthermore, because vermicomposting requires very little space, apartment dwellers and homeowners without room for an outdoor compost pile can use worms as a low-odor, low-mess means to produce compost. (See References 1)
Monitor your household's daily production of organic wastes in order to determine the number of worms you need. Worms consume food scraps, paper and plant-based materials like houseplant clippings. Weigh your household's daily output of these materials during a normal week. You need 1 lb. of worms for every 1/2 lb. of compostable garbage your household produces in a day. (See References 2)
Choose a container to act as a worm bin. Wooden and plastic containers both work but should have holes drilled in the sides and bottom for aeration and drainage (see References 3). Worms are sensitive to light, so your container should have a cover (see References 4). Provide 1 square foot of container for every pound of garbage produced by your household in one week (see References 3).
Fill the bin three-quarters full with bedding. Bedding can include shredded newspapers, fall leaves, straw, aged manure and garden soil. Worms eat the bedding, so providing them with a variety results in healthier compost. Moisten the bedding until it reaches a moisture level equivalent to that of a wrung-out sponge. (See References 3)
Add 1 tbsp. of grit, which worms use to digest their food. Grit can include sterilized sand or soil, rock dust or oyster flour. (See References 4)
Add the worms to the worm bin and allow them to bury themselves in the bedding.
Bury food scraps in the bedding. Choose different locations each time you add to the worm bin. Burying scraps reduces problems with odors and pests. Avoid adding meats, dairy, grains, oily foods and acidic foods like citrus to your worm bin.
Separate finished compost from the worm bedding, placing it to one side of the bin and adding new bedding and food scraps on the other side. Worms will migrate into the new bedding, leaving the compost worm-free and ready to use. (See References 3) You can expect your first compost harvest in three to four months (see References 2).
Use finished worm compost as potting soil or cover the soil of existing houseplants with a layer of compost. You can also add worm compost to outdoor garden soil or sprinkle it on your lawn to boost organic matter and nutrients in the soil. (See References 3)
- U.S. Environmental Protection Agency; Backyard Composting: It's Only Natural; October 2009
- U.S. Environmental Protection Agency: Vermicomposting; August 2010
- Canada's Office of Urban Agriculture; Composting With Red Wiggler Worms; February 2011
- CalRecycle: Vermicomposting --- Composting With Worms; December 2010