Vermicomposting: A Beginner’s Guide
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Try composting with worms to create a vermicompost superfood for your garden!
Rhonda Sherman, founder and director of North Carolina State University’s two-acre Compost Learning Lab (complete with a dedicated worm barn!) says, “Food waste is the number one segment of the waste stream that’s going in the landfills. Keeping your food waste out of the landfill is so easy to do with composting and vermicomposting.”
What Is Vermicompost?
Vermicompost is the byproduct of a process where earthworms and microorganisms consume and break down organic materials and convert them into a rich soil enhancement and source of plant nutrients. Commonly vermicomposted materials include:
- Vegetable and fruit scraps (but not citrus fruits);
- Tea bags;
- Coffee grounds;
Items that can’t be vermicomposted include animal by-products such as fat, bone, dairy, eggs, meat, fish or pet poop. It may take worms longer to process woody or dry scraps like stems or the outer layer of an onion. The worms will eat paper as long as it’s thin or shredded. But they won’t eat plastic or fabric tea bags, coffee filters or the labels placed on produce by grocery stores.
Vermicomposting vs. Regular Composting
In a traditional compost pile or bin, bacteria, microorganisms and moisture break down kitchen and yard scraps into a light organic material. This type of compost requires heat, generated by the bacteria, and time to cool down and cure, which can take six months or more.
In vermicomposting, a smaller, shallow, dark bin with ventilation contains worms living in cool, moist bedding material. These worms eat the scraps that are added to the bin weekly and generate castings (a sanitized term for poop) within two to three months.
Pros and Cons of Vermicomposting
- Vermicompost contains plant growth hormones, humic and phobic acids. All help seeds germinate faster, develop better roots and strengthen plants.
- These same compounds (or ones yet to be discovered) seem to protect plants from pests and disease.
- In testing the vermicompost effect on turnips, Sherman found that plants grown in 20 percent vermicompost were about the size of baseballs, compared to the ping-pong sized root vegetables grown without vermicompost.
“[Vermicompost] does incredible things for plants,” Sherman explains.
- You can only add about an inch of food scraps, preferably once a week. If you add too many scraps, you risk the bacteria multiplying and the bin heating up like a traditional compost pile. If you have a lot of food waste, it’s wise to have a traditional compost pile as well.
- You don’t want to add onion, garlic or other pungent scraps unless your bins are kept outdoors where the smell won’t be offensive.
- You are working with living creatures and need to take care of them by providing enough moist bedding, air, warmth and food.
How to DIY Vermicompost
Sherman, who has shared her expertise with people from around the world through conferences, workshops and The Worm Farmer’s Handbook, offers these tips for at-home vermicomposting.
DIY Vermicomposting Bin
- Start with a dark plastic storage container with a tight-fitting lid. The box should be at least eight to 14 inches deep.
- Drill small holes for air circulation around the upper inch or two of the bin. Drill groups of three holes (1/2-in. or less) about five inches apart. Or, you can drill a three-inch hole with a hole saw on both short sides of the bin. Plug three-inch holes with soffit vents.
- Drill six 1/4-in. drainage holes in the bottom of the bin.
Affordable Vermicomposting Bins to Buy
These specialty bin systems are created for vermiculture:
- The Worm Factory 360 incorporates stackable plastic worm bins.
- The Maze Worm Farm is another stacked setup.
- The Urban Worm Bag offers a fabric bin, plus accessories and kits.
Vermicompost Bedding Material
Prepare your worm bin by adding four to five inches of bedding material, such as shredded paper, brown leaves, finished traditional compost or rotten manure.
If you use paper or dried fall leaves, make sure you soak them in a bucket of water and gently wring them out. You can also mix in a handful of soil with shredded paper or leaves to make it a little more dense.
If using finished compost or rotted manure, which is dirt-like in texture, Sherman says add enough water so that it’s damp but not soggy or waterlogged. You’ll know it’s not overly soggy if you can fluff up the material with a garden fork or trowel.
Pro tip: When you add kitchen scraps, cover them with at least two inches of bedding, which keeps fruit flies and other critters from finding it.
To svermicompost successfully, think of it as worm farming. You are taking care of living creatures and providing air, food, shelter and comfort. The ideal temperature for worms to create compost is between 59 F and 77 F.
The most likely indoor places to keep your bin(s) are the basement, utility room or attached garage. Outdoors is an option, but you’ll need shade to protect the worms from intense heat.
If you live in a cold climate, insulate your worm bins with blankets, straw or other materials to keep them comfortable. They will survive temperatures as low as 32 F and as high as 95 F, but they’ll need at least four inches of bedding for insulation.
And now for the stars of the show. Only a few specific worms, among hundreds of varieties, can successfully compost your kitchen scraps. Red wigglers (aka Eisenia fetida) rank as the favorite go-to composters. European night crawlers are another option. You’ll need a pound of them, which is about 1,000 red wigglers.
Buy worms from specialty suppliers such as Worm Composting Headquarters or Meme’s Worms. They can be your biggest investment at $45 to $75 per pound. Have your bin ready to go before the worms arrive.
Some ready-made worm composting setups will have a filter to shake out the finely textured worm castings. Or you can use a screen to filter out the castings without losing worms.
If you have a homemade bin and have been composting for six months, you can start putting food scraps on just one side of your bin so you can scoop out worm castings from the other side. A worm comb or a garden fork used gently can help you sift through the castings to remove worms as well.
If you aren’t going to use the vermicompost right away, put it in a plastic bag that has a few holes to allow air in but retain moisture.