Vermicomposting Puts Worms to Work

What is Composting with Earthworms?

Instead of traditional outdoor composting using microorganisms, like bacteria and fungi, this method uses red wiggler earthworms (Eisenia fetida, formerly E. foetida) to convert food waste and other organic materials to compost. Also called vermicomposting, the final product is called worm castings or vermicompost. Worm castings enhance soil by reducing erosion and increasing porosity and water-holding capacity. It may contain 4% more nitrogen than traditional compost and, thus, increase crop yields. It may also decrease plant diseases and attacks by pests.

What Materials are Needed?

You'll need a bin and indoor space to keep it. Lots of shredded paper bedding moistened with water, fruit, and vegetable kitchen scraps, and a specific species of earthworm to do the work for you. You can purchase a vermicomposting bin or make your own.

Worm Bins

Earthworms avoid light, so select a dark-colored, opaque bin with a lid. Deep, narrow containers, like five-gallon buckets or garbage cans, do not work well because composting earthworms are surface-dwellers. I suggest starting with an inexpensive, shallow plastic tote, about 14 gallons in size. Use a one-quarter-inch drill bit to make ten drainage holes in the bottom and another ten holes in the sides near the top rim for ventilation. Place a tray or another bin under the worm bin to protect the area. Use deli containers or lids to lift the bin above the tray. These spacers will allow any leachate to drain out. Dilute the leachate with water (10:1, water to leachate) and use this nutrient-rich liquid to fertilize your plants. Wooden boxes or drawers may be used as worm bins, too. Eventually, they will decay from the moisture. Avoid pressure-treated wood, cedar, cypress, or redwood, as these are toxic to earthworm workers. Placement of the worm bin is essential. Red wigglers enjoy the same indoor temperatures that we do, 60° to 75°F. Avoid placing the bin near heat or cold extremes. Avoid the laundry room, as washing machine or dryer vibrations may drive the worms from their bins.

Earthworms

Not all earthworms are good at living in worm bins at household temperatures. Anglers store their nightcrawlers (Lumbricus terrestris) in a refrigerator. Nightcrawlers live deeply in the cooler areas of the soil. Red wigglers live near the soil surface and among the leaf litter in warmer conditions. This trait makes red wigglers good indoor companions for us.

In Pennsylvania, most of our earthworms are non-native. Our native earthworms were driven out about 15,000 years ago by the cold temperatures of the last glacial period. Most non-native earthworms from Europe have not negatively impacted our habitats. You may have heard of jumping worms (Amynthas spp. and Metaphire spp.), which were accidentally introduced a few years ago from Asia. These newly arrived non-native earthworms are considered invasive and have a different appearance and behavior than our nightcrawler and red wiggler earthworms. Read Penn State Extension's "Look Out for Jumping Earthworms" to learn more.

If you have questions about earthworms' benefits, types, and biology, Penn State Extension's article "Earthworms" answers them.

You can purchase red wigglers online or from a local bait dealer. Don't purchase a few dozen worms in a little bait cup! Instead, ask local dealers when they are placing their next order. Request that they include about one pound or 1,000 Eisenia fetida with their next order for you. Be sure that they understand this specific species is what you need. A pound of red wigglers in an established worm bin will consume about a half-pound to one pound of scraps each week!

Bedding

Narrow newspaper strips make excellent bedding for red wigglers in a worm bin. Tear or cut sheets of newspaper into strips less than one inch wide. If the paper does not tear straight, turn the sheet 90° and try again. Avoid using paper shredders that cross-cut for worm bedding. These paper bits are too small and will pack down. Used printer and schoolwork papers make great bedding. You can say, "The worms ate my homework!" Remember to remove the plastic windows from mailing envelopes before shredding them for the worm bins.

Publishers have used non-toxic soy-based inks for over twenty years. Avoid using glossy magazines and catalog pages. Never use paper with shiny metallic designs.

Add some crushed autumn leaves, bits of chopped straw, and perhaps some small pieces of cardboard. Add sawdust very sparingly, as it tends to compact. These materials decompose slowly but will help regulate moisture and aeration.

You'll need about six inches of bedding on the bottom of the bin. Use a spray bottle to moisten the bedding with water. Mix it until it is damp, but not wet, throughout.

Food

Our hard-working red wiggler earthworms are vegetarians. They love salad scraps but without dressings! Trimmings from fruits and vegetables are their favorites. Potato peelings in moderation are okay. Coffee grounds, filters, and tea bags are delicious to a red wiggler, but please remove the staples or plastic strings. Cereal, bread, and pasta in small amounts are okay, but no sauce or butter. From time to time, add a very finely pulverized eggshell. Never add meats, eggs, fats, oils, dairy products, or citrus peels.

Smaller pieces decompose faster. I keep a container for scraps in my freezer until the twice-weekly feedings. The freezing helps break the cell walls of the plant material so it decomposes more quickly in the worm bin. It also prevents icky, rotting scraps on my countertop. If the freezer container fills before the worms are fed, the rest goes to my outdoor compost pile or the "green bin" for municipal composting.

To add food to the worm bin, dig a small hole in the bedding, add the food, and then cover it with bedding.

Harvesting Vermicompost

After a few months, push all the worms and bedding to one side of the bin. Add moistened fresh bedding and a small amount of food to the other half of the bin. The hungry worms will slowly migrate from the old, processed vermicompost to the new area in the next few weeks.

If you are in a hurry for the vermicompost, dump the worms and bedding onto the lid. Use a desk lamp to shine a bright light onto the pile. The worms will go deeply into the pile. Scrape off the vermicompost every hour or so, forcing the worms ever more deeply into the pile. Soon, there will be a pile of vermicompost for your plants and a separate pile of worms ready to return to work in fresh bedding.

If you are concerned about introducing red wigglers into your garden, freeze the vermicompost for one to four weeks to kill any earthworm capsules (egg cases) and tiny thread-like earthworms. In most parts of Pennsylvania, red wigglers do not survive our winters.

Problems

My biggest vermicomposting problem was "brassica overload." Adding too much cabbage, broccoli, cauliflower, and kale scraps (family Brassicaceae) to the worm bin created a very unpleasant odor. The worms didn't mind, but the family did! We became careful to limit those veggies.

The earthworms will naturally reproduce, and you will have red wigglers to share with others, or you can create another bin for yourself. To produce worms, read about Worm Production by Penn State Extension.