Home Composting


Worm Composting on the Rise at Home

Copyright by Jim Jensen, YELM Earthworm & Castings Farm, 1998, yelmworms@aol.com. Permission granted to copy or post with complete attribution in whole, without addition, deletion, or substitution.

A worm bin should have about one square foot of surface area for each pound of food wastes added per week. For example, a two-foot by four-foot box is large enough for eight pounds of kitchen scraps a week—the amount produced by two or three adults. Generation of food scraps varies widely between households, so you may want to weigh your scraps for a week or two before deciding what size or how many bins you want to build.

Fill the worm bin with moist "bedding," which provides the worms with balance in their diet and a damp place to live. Composting food scraps without bedding can produce bad odors and a slimy mess. Common bedding materials include fall leaves, shredded newspaper or corrugated cardboard, old straw, coarse sawdust, and aged dairy or horse manure. Rabbit manure also works well. Moisten dry bedding materials by immersing them in water for several minutes before adding them to the worm bin. When the bedding is thoroughly wet, remove it from the water and wring out or drain excess water. Moist bedding should feel damp like a wrung out sponge.

Fill the bin to the top with loose bedding. This gives the worms maximum room to grow their population. Pull apart any compacted paper strips before adding them to the bin. If brown leaves or sawdust are used they may need to soak longer to become saturated.

Feed worms by burying vegetative food scraps in holes dug into the bedding. Bury scraps in a different spot each time to provide the worms with a balanced diet. Always cover food wastes with a few inches of bedding or worm compost (called castings) to discourage flies and odors. For best results, think of worms as strict vegetarians. Give them scraps of fruits and vegetables, grains, old bread, coffee grounds, used tea bags, and egg shells. But leave out oily foods, meat, seafood, or dairy products.

Every 3 to 6 months push the old bedding and decomposing scraps to one side of the bin, rebed the empty side, and start burying food wastes in the fresh bedding. Allow the older scraps to finish composting for another month or so before harvesting.

Harvesting Worm Castings or Worms

One of the real benefits of worm composting is producing worm excreta (known as castings) for use in your garden. After a few months, worm castings from a worm bin will look dark and rich, quite black. To harvest castings for garden use, simply move nearly finished compost to one side of the bin and fill the empty side with fresh bedding (composting reduces the volume of the wastes by over one half). For the next six weeks bury food wastes only in the newly bedded side of the bin. The worms will migrate over to the fresh food in the newly bedded side as the food on the other side finishes decomposing. When the old bedding and food scraps are completely composted, the castings can be harvested and replaced with fresh bedding. It takes from three to six months for fresh bedding to decompose. Thus a worm bin can complete two to four cycles each year.

Harvesting worms for fishing is easy. Just open the bin and pick a handfull out of the bedding. To harvest more worms, take a few shovelfulls of castings out of the bin and make small piles on a piece of plastic out in the sun or under a bright light. Let the piles sit for ten minutes, then pull away the surface layer of castings until you see worms. Repeat the procedure until the worms are concentrated at the bottom of the piles and are easy to harvest.

Preventing Trouble

Worm composting bins are relatively trouble free. The most common problem with worm bins is fruit flies in summer. Fruit flies can be kept to a minimum by always covering fresh food wastes with a few inches of bedding or castings, and by covering the bedding with a sheet of plastic or newspapers tucked in around the edges. If the worm bin smells bad, it probably has too much food waste in it, is too wet, or there is cheese or other animal products present. To eliminate bad odors remove excess or inappropriate wastes and add fresh bedding.

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