Worm composting, or vermicomposting, uses the digestive power of earthworms to recycle kitchen scraps into nutrient-rich compost. Worm composting is a fascinating process that makes a great family project.
Like traditional composting, worm composting works by creating an ideal environment for “compost critters” such as worms, fungi, bacteria, and other insects to break down and recycle organic matter. The resulting compost benefits plants by increasing the availability of nutrients in the soil, improving soil drainage, and offering natural control over plant diseases and pests.
Worms may be purchased for composting through mail order or from local worm farms. Red Wigglers (Eisenia fetida) are ideal for composting; they have short lifespans, reproduce quickly, and tolerate a wide range of environmental conditions, making them easy to care for. Found in nature eating leaves on the forest floor, consuming barn litter, or in piles of garden waste, red worms thrive in a bin environment. Once you establish a healthy environment for your worms, they will begin to multiply. It’s not uncommon to see eggs, immature worms, and adults in worm bins simultaneously.
The size of the bin you choose depends on the amount of food scraps you produce. One pound of worms contains approximately 1,000 worms, which can consume about one half pound of food scraps per day. A typical family of four people produces approximately 1 pound of kitchen scraps per day, or 5 to 7 pounds a week. Based on these estimates, most people will need 2 pounds of worms and a bin with at least 5 square feet of surface area to begin.
Before choosing the type of bin to use consider where it will be located. The ideal placement is a cool, shaded, outdoor spot protected from excessive rain and convenient to the kitchen. Worms thrive in temperatures between 59-77 degrees. There is no need to worry about winter temperatures in the Lowcountry, since the heat generated by the decomposition in the bin will keep the worms warm enough, even on our coldest nights.
There are many types of bins available including several do-it-yourself types. Simple plastic bins are the most basic and consist of plastic storage tubs with drainage holes stacked inside one another. Instructions for this easy-to-set-up, inexpensive bin may be found on at http://whatcom.wsu.edu/ag/compost/easywormbin.htm
Plans for homemade wooden bins are widely available. These bins measure 1 foot deep by 2 feet wide by 3 feet long. They have added drainage holes in the bottom and sides with a hinged lid. Wooden bins have fewer problems with odor and moisture than the plastic bins.
To set up a worm bin, begin with an 8-inch layer of moistened, shredded newspaper or office paper, and finished compost or leaves. Moisten bedding so that it feels like a damp sponge. Pull aside the bedding in one corner of the bin and gently add worms. Bury 1 to 2 pounds of food scraps along with each pound of worms and add a 2-inch layer of new bedding as old bedding is consumed.
Feed worms a plant-based diet such as fruit and vegetable scraps, peels, eggshells, cereal, bread, pasta, and coffee grounds. To avoid attracting flies, mice, rats and other vermin, never put meat, oil, dairy, or pet feces into bins. To avoid fruit fly and odor problems bury food under the bedding.
Three to six months after the bin is set up, harvest compost using one of several methods, such as the “dump and sort” method. Divide contents of the bin into small cone-shaped piles on a tarp in a brightly lit area, wait about 20 minutes, and the worms will move away from the light and into the center of each pile. Brush compost off the top until a ball of worms remain which can be returned to the bin.
For large bins, move contents to one side, and add food and bedding exclusively to the empty side for a few months. The worms will move to the fresh bedding and food, leaving behind finished compost for you to scoop up and use in the garden.
To use your compost, blend it with potting soil to make up 1/3 of the total volume and add it to backfill when planting flowers, vegetables, trees and shrubs. Or you can spread 1 to 2 inches of compost around the base of plants.
To make “compost tea,” steep worm compost in water overnight to solubilize nutrients and use this mixture to fertilize your plants.
For complete instructions, a reading list and resources, including a troubleshooting guide, go to www.clemson.edu/extension/hgic/plants/other/compost_mulch/hgic1607.html
Amy L. Dabbs is the urban horticulture extension agent and Tri-County Master Gardener coordinator for the Clemson University Cooperative Extension. Send questions to firstname.lastname@example.org.