Vermiculture: Composting with Worms

Why send organic waste to landfills when you can compost? This is a sensible solution, but maybe you aren't able to compost outdoors or you live in an apartment. Try composting with worms indoors, which is known as vermiculture.

"Vermicomposting has many advantages," said Susan Harrison, Master Gardener at Penn State Cooperative Extension-Bucks County. "You can compost all year—the decomposition process is non-stop and it's not dependent on the weather since it's done indoors. Your food scraps help create worm manure full of rich nutrients that can enrich your soil. You can eliminate the need for chemical fertilizers and reap the benefits of healthier plants and better tasting vegetables."

For vermicomposting success you must use the correct type of worms, create the proper environment for the worms to thrive, feed the worms properly, and maintain the worm bin.

Composting with Worms

 Worms are the key ingredient. Estimate one pound of worms for every square foot of surface area. One pound of worms will decompose half a pound of food scraps (an average amount for a household of 2-3 people). Use redworms (Eisenia fetida) or red earthworms (Lumbricus rubellus). These worms live indoors in a bin at temperatures between 50 to 80 degrees, not outdoors in soil.

"You can purchase redworms at a bait shop, only if they can tell you the Latin name," Harrison said. "Better yet, get them from a friend who vermicomposts." Harrison also suggests visiting the FindWorms.com website. Redworms breath through their skin and need moisture, a dark location, and a variety of fruits and vegetables to eat. Earthworms such as night crawlers cannot survive in a worm bin.

Potential food sources include fruit and vegetable scraps, pulverized eggshells, coffee grounds, tea bags, and items such as stale bread in moderation. Avoid meat, dairy products, and greasy foods. Use little or no citrus peels because they can be toxic to the worms.

Worm Bin Construction & Maintenance 

"You don't need to buy a fancy container for worm composting," Harrison said. "I like to use plastic totes I have around the house."

Harrison advises using an inexpensive 10- or 18-gallon opaque plastic bin with a lid. The bins require good air circulation and drainage.

How to create a bin:

1. Drill drainage holes on the bottom and air holes on the sides around the top of the bin (1/8" is good—about 15-20 holes total).

2. Put wood strips on the bottom to elevate the bin for drainage. Put a drip tray on the bottom (your plants will enjoy this "compost tea"). As an alternative, you can sit your plastic bin on bricks or wood blocks.

3. Create bedding: Fill the bin one-third of the way with shredded newspaper or cardboard that is moist. Use black and white newspaper printed with soy-based ink—no glossy or colored papers. The bin needs good air circulation so do not compress the newspaper—keep them fluffed up. The bedding should be evenly moist but not dripping. "You want the moisture in the paper to feel like a wrung out sponge," Harrison said.  

4. Add a handful of fine sand for grit for the worms' digestion process and mix in.

5. When you add food waste, bury it under the newspaper. Let sit for about a week or so. You are growing microbes for the worms to eat.

6. Add worms and cover the bin. Worms require a dark location to survive.

7. Feed the bin but don't add to much food. Make sure to bury the food in the bedding. Watch to see what breaks down and how long. If the bin develops an odor, you probably have too much food in the bin or too much moisture and not enough air, or the wrong kind of food. Over time you will need to add more bedding as it decomposes.

8. Harvest the worm castings three or four times per year. Push the finished compost to one side of the bin and start adding fresh food scraps and bedding to the other side. The worms will migrate over and you can lift out the finished side.

Use your finished compost as a soil conditioner for houseplants, gardens or lawns. Harrison recommends, Worms Eat My Garbage, by Mary Appelhof as an excellent resource.

Enjoy vermicomposting and let us know about your own composting experiences in the comments.