Composting is a natural process where kitchen and yard wastes decompose into a dark, nutrient-rich, earth-smelling soil conditioner. Perhaps you've considered backyard composting but live in a high-rise or don't relish the thought of tramping through your garden in the middle of a winter blizzard. Or perhaps you want to compost indoors in your school or office. If so, vermicomposting may be just the answer for you.
What is Vermicomposting?
Vermicomposting is simply composting with worms. The best kind of earthworm to use is the redworm (a.k.a. red wiggler). These worms are incredible garbage eaters! They eat and expel their own weight every day, so even a small bin of redworms will yield pounds of rich sweet-smelling compost. Finished compost can be harvested in as little as two to three months.
Redworms are extremely prolific. It takes about three weeks for fertilized eggs to develop in a cocoon from which two or more young worms can hatch. In three months the worms are sexually mature and will start breeding. Within a year you'll be able to give worms away to get a friend started!
What do I need?
• a Bin
• Buy a plastic storage bin (with a lid) from a hardware or department store and convert it into a bin for worm composting. Drill eight to ten holes (approx. 1 cm or 1/4") in the bottom for drainage. Line the bottom with fine nylon mesh to prevent the worms from escaping. Place the bin on blocks with a tray underneath.
• Build one yourself with our Vermicomposting Bin Instructions
• Purchase a commercial one from "Vermicomposting Suppliers".
The container should be shallow (8 - 12" deep), and provide one square foot of surface area for every pound of food waste per week (i.e. six pounds of food waste requires a bin 2' x 3').
|1 or 2
||1' x 1.5' x 2'
|2 or 3
||1' x 2' x 2'
|4 to 6
||2 - 3 lbs.
||1' x 2' x 3.5'
• Check for "Vermicomposting Suppliers" for companies that sell worms.
• Redworms can survive and breed in many kinds of bedding materials. The important thing to remember is that the red wiggler will eat its own bedding. Materials such as hand-shredded newspaper, composted manure, dampened peat moss, or leaves can all be used. Make sure to mix peat moss with other bedding as it is too acidic to use alone. You can also purchase prepared bedding which may be machine-ground paper either alone or mixed with loam.
• Dampen the bedding until the moisture level is like a well-wrung sponge. Fill the bin 3/4 full with bedding. Add the worms. Since worms don't like light, they will quickly crawl down into the bedding.
What and how do I feed them?
• Worms will eat just about any type of kitchen waste including vegetables and fruits, coffee grinds, tea bags and egg shells.
• Avoid putting in meats and fats.
• You can feed your worms every few days, or once a week if you prefer.
• Simply pull aside some of the bedding, bury the food waste, and cover it with bedding. Each time you feed the worms, choose a different location to bury the food.
• Note: egg shells will maintain the bedding at a safe pH level. Without them the bedding may become too acidic. When adding egg shells you should:
• let the shells dry out
• crush them finely with a rolling pin
• sprinkle approximately one tablespoon per pound of worms onto your bedding every week.
Can worms live outside during colder months?
• Worms prefer temperatures between 40 and 80 degrees Fahrenheit. If you live in an apartment building they can live quite happily out on the balcony until temperatures drop to 40 degrees. After that they should be taken indoors.
• If you use an insulated worm bin, however, the bin can remain outdoors year-around. Insulated bins are available commercially or you can make your own.
How can I harvest the finished compost?
• After about three months you'll notice that the volume of materials has dropped substantially and the original bedding is no longer recognizable. This means it's time to harvest the finished compost and add fresh bedding.
• There are several ways to harvest:
1.) Move the contents of the bin to one side. Add fresh bedding to the vacant side. Put food scraps into the fresh bedding only, so the worms will move from the finished compost in search of food. After one or two weeks, remove the finished compost.
2.) Dump the contents of the bin onto a large plastic sheet, and separate into small cone-shaped piles. Place a bright light above the sheet. The worms will move down away from the light. Remove the finished compost from the top of each pile. A small pile of worms will remain at the bottom. Place these into the bin with fresh bedding.
3.) Remove the entire contents of the bin. Put in fresh bedding and food. Place a large piece of burlap over the bin ensuring that the burlap overhangs the edges of the bin. Place the contents of the bin that you have removed back on top of the burlap. With the lid off, shine a light directly over the bin; try a fluorescent or halogen light. Gradually the worms will move down through the burlap into the fresh bedding. You can then remove the finished compost from the top; do this gradually - 1 or 2" a day. This process will take about a week altogether
4.) A variation on this method is to put only one inch of material at a time onto the burlap. The worms will burrow down very quickly and you can then remove the finished compost. Repeat this process until you have harvested all the finished compost.
• Note: For methods 2) and 3), don't feed the worms for one or two weeks prior to harvesting.
How can I use the finished compost?
• Vermicompost will provide nutrients to your plants and will help the soil hold moisture. It can be used in a number of different ways:
• Sprinkle into a seed row when planting.
• When transplanting, add a handful of soil to the hole you have dug for the plant.
• Use as a top dressing, sprinkling the compost around the base of your plants.
• Mix with potting soil (half and half) for house plants.
What can I do about fruit flies in and around my worm bin?
- The best approach is prevention. When you add food scraps, always bury them under the bedding. Be sure they are well covered with about 3" of bedding material. As an extra measure, you can also put a bit of fresh bedding on top.
- Keep a tight lid on the container you use to store food scraps before adding them to the bin. This will prevent flies from laying eggs in the scraps.
- If a lot of fruit flies fly out of the bin when you lift the lid, you can suck them up with a vacuum cleaner.
- Use a trap. Pour a half-cup of beer into a small glass jar. Place a plastic bag over the mouth of the jar with one corner reaching down into the jar. Poke a small hole in the corner of the bag with a pencil. Secure the bag around the rim with a rubber band. Fruit flies will be attracted by the beer, make their way through the hole, and be unable to get out. (From "Worms Eat My Garbage")
Will a worm bin smell?
It is unlikely that your worm bin will have an unpleasant odour. If it does, there are a number of possible causes and steps you can take to remedy the problem:
Problem: You have overloaded the bin with too many food scraps.
Solution: Give the worms a break and don't add any food scraps for a week or so.
Problem: The bedding is too wet and compacted.
Solution: Check the drainage holes to make sure they are not blocked and drill more holes if needed. Gently stir up the entire contents to allow more air in, and add some fresh dry bedding.
Problem: The bin is too acid.
Solution: Add very finely crushed egg shells to neutralize the acidity.
Problem: The contents of the bin have not been harvested in over three months.
Solution: Harvest the bin.
This design sheet was originally produced for the Community Composting Education Program in Seattle, Washington.