Vermicomposting: Composting with Worms
Vermicomposting is the process of using worms and micro-organisms to turn kitchen waste into a black, earthy-smelling, nutrient-rich humus.
You Need 5 Basic Ingredients to Start Vermicomposting:
- a container
- bedding (aka shredded manuscript paper)
- nonfatty kitchen scraps.
Worm boxes can be purchased or made out of plastic storage containers.
Plastic storage containers are convenient and come in a variety of sizes. These containers are easily transported and are a nice alternative to heavier wood bins. Depending on the size of the container, drill 8 to 12 holes (1/4 – l/2 inches) in the bottom for aeration and drainage. A plastic bin may need more drainage — if contents get too wet, drill more holes. Raise the bin on bricks or wooden blocks, and place a tray underneath to capture excess liquid which can be used as liquid plant fertilizer.
The bin needs a cover to conserve moisture and provide darkness for the worms. If the bin is indoors, a sheet of dark plastic or burlap sacking placed loosely on top of the bedding is sufficient as a cover. For outdoor bins, a solid lid is preferable, to keep out unwanted scavengers and rain. Like us, worms need air to live, so be sure to have your bin sufficiently ventilated.
I used to have a plastic storage container bin, but this year I broke down and bought a Worm Factory.
Its chief advantage is that it is easier to harvest the compost. See below.
Here is where those old manuscripts come in. It is perfect for worm bedding! It retains both moisture and air while providing a place for the worms to live. Shredded corrugated cardboard is also good, but difficult to find.
The amount of bedding depends on the size of the box. A 2-by-2 foot box will need between 4 and 6 pounds of dry bedding, a 2-by-3 foot box will take 9 to 14 pounds. No matter what the size, the bin should be 2/3 filled with “fluffed” prepared bedding (see below). For smaller bins, experiment–if you prepare excess bedding, it can be dried, stored and used another time.
Prepare the Bedding:
Water is needed to moisten the bedding. Place the dry, shredded bedding in a large container and add water until it covers the bedding. Allow the bedding to absorb as much water as possible before putting it in the worm bin. This could take from two to 24 hours, depending on the bedding used.
Before putting the bedding in your bin, squeeze the water out from the bedding as much as possible. The bedding should feel like a well-wrung washcloth. Place the bedding in the bin and fluff.
Your bedding needs to remain moist. If it is drying out, mist the paper with water from a spray bottle and dampen the bedding again.
The worms used in vermicomposting are called redworms (Eisenia foetida), also know as red wigglers, manure worms, red hybrid or tiger worms.
- You can order them on the internet, e.g. Amazon
- You may be able to find them in a bait store
- If you know someone who has an established supply, they may be willing to sell you some of their worms.
What About Nightcrawlers? Do not try to use nightcrawlers or other native worms to stock your worm bin. These worms depend on cooler temperatures and an extensive tunneling system to survive. They will die in your worm bin
Why Redworms? Redworms prefer temperatures between 55 and 77 degrees Fahrenheit and are suited to living in a worm bin. The temperature of the bedding should not be allowed to get below freezing or above 84 degrees.
How Many Worms Do I Need? The amount of worms needed will depend on the amount of kitchen waste generated per day. One pound of redworms will easily take care of each half-pound of garbage. To add worms to the bin, simply scatter them over the top. The skin on the worm reacts to light and they will immediately work their way down into the bedding to get away from the light.
The kitchen waste fed to worms can come from a variety of sources, including all vegetable and fruit waste (don’t be surprised that some seeds may germinate and potato peels with eyes sprout), pasta leftovers, coffee grounds (with filter) and tea bags. Worms may have a problem with garlic and onion skins. Worms have a gizzard like chickens so fine grit should be added to help the worms digest food. This gritty material includes cornmeal, coffee grounds and/or finely crushed egg shells (dry the shells and then crush). Avoid large amounts of fat, meat scraps or bone. Some sources feel that a small amount of meat and eggs will provide protein to the worms, but be careful you don’t overdo it and know that you may attract rodents.
Adding Kitchen Scraps:
First, and foremost, START SLOWLY. It will take time for bacteria to form and your bin can quickly become very smelly if you add too much food, too fast. In the beginning, add a very small amount of gritty material (see above) and a small amount of vegetable matter. Don’t worry about the worms starving because they will be eating bedding as well. You can gradually increase the amount of food as the bin becomes established.
The easiest method is to spread the scraps in a thin layer on top of the bedding. If the bin is kept in a dark place or covered, the worms will come to the surface to eat. You can also pull back a small amount of bedding in the bin and dump in the scraps. Cover the scraps with an inch of bedding. Start at one corner of the bin and bury garbage in a pattern to fill in all the spaces. By the time you get back to the first burying spot, the worms will have composted most of the waste.
If you notice odors, cut back on the amount of food or try chopping the food up into smaller pieces. Note: citrus does have a strong odor and the peelings seem to last a long time in the bin. Bins seem to be more manageable when there is less fruit and citrus and more of the leafy vegetables.
Harvesting the Compost:
Given the right environment, the worms will go to work to digest the kitchen scraps and bedding faster than any other compost method. The material will pass through the worms’ bodies and become “castings.” In about 3-4 months, the worms will have digested nearly all the garbage and bedding and the bin will be filled with a rich, black natural fertilizer and soil amendment. Compared to ordinary soil, the worm castings contain five times more nitrogen, seven times more phosphorus and 11 times more potassium. They are rich in humic acids and improve the structure of the soil.
To keep your bin going, you will need to remove the castings from time to time and there are several ways to go about it. One way to do this is to shine a bright light into the bin. The worms are sensitive to light and will move to the lower layers of the bin. Remove the top layer of casting by using your hands or a sieve. Each time you remove some bedding, the worms will be exposed to the light and they will keep migrating down to the bottom of the bin. Pick out any wigglers or worm eggs (small, opaque cocoons) and return them to the bin. Refill the bin with fresh layers of moist bedding and food.
Another method of harvesting composts is to push the black, decomposed material to one side of the bin, and fill the other side with new, moist bedding and kitchen scraps. Then wait several days. The worms will migrate to the freshly filled side of the bin and you can just scoop out the finished compost. Make sure you pick out any wigglers or worm eggs and return them to the bin.
If you purchase a Worm Factory like mine, harvesting is easier because of its multi-tray design. Worms begin eating waste in the lowest tray, and then migrate upward as food sources in that tray are exhausted. By allowing worms to migrate upward, the worms separate themselves from the finished compost that is ready for the garden.
Using the Compost:
For potted plants, add a thin layer to the top of the potting soil. You can also add the compost directly into your soil mix when repotting. In the garden, simply add it to your compost pile or work it into the ground around the base of each plant. The compost is very mild and you won’t have to worry about accidental burning or overfertilizing.