How to vermicompost
Vermicomposting is similar to regular composting, except that it uses worms to break down organic waste. The worms digest the organic matter then expel “worm castings” or “worm manure”, which is rich in nutrients. The nutrient level found in worm compost is often much higher in concentration than in garden compost. It makes a great top dressing for gardens and potted plants, and can be mixed with potting soil. It also makes a great seed starter, but it should be combined with other soils because it is too rich for the young seedlings.
Why vermicomposting instead of a regular compost pile?
Vermicomposting is great for apartments and those who live in the city with small yards. Where there is no room for a large compost pile, composting with worms is the next best thing. It doesn’t take up a lot of space. A worm compost bin can be indoors or out. It can easily be brought indoors during the winter, so you don’t have to go outside to get rid of your food waste. Another advantage is that the soil doesn’t need to be turned regularly to provide oxygen; the worms do it for you! And the resulting organic matter is even richer in nutrients than a regular compost pile.
The only disadvantage to vermiculture is that the worms can only work so fast. You cannot put large amounts of food waste into the worm bin because they cannot eat it quickly enough. It will start smelling and may attract flies and pests. It is best to slowly add food scraps every few days. If you have a lot of yard and food wastes, it would be best to begin a compost pile in the backyard. (Read how to at How do you compost?).
What kinds of worms are in a vermicompost?
There are two kinds of worms that are used for vermiculture; the brandling worm (Eisenia foetida), and red wigglers or redworms (Lumbricus rubellus). These kinds of worms are not typically found in garden soils, but are well adapted to manure and compost piles. Your typical earthworm (Lumbricus terrestris) should not be used because they thrive in ordinary soils.
You can purchase the brandling worm and red wigglers at Compost Mania.
Where should the worm compost bin be located?
Your worm compost can be indoors or out, but be sure that that temperature stays between 40-80ͦ F (Optimally between 55-77ͦ F). You don’t want your worms to freeze or bake. If it gets cold in the winter, you can bring your worms in the garage and place them by a hot water heater. If your bin is outdoors, make sure it is not in direct sunlight or it will dry out quickly. You also may want to put a lid on it to keep moisture in and animals and bugs out.
How do I set up the vermicompost bin?
You bin can be made out of wood or plastic, but wood is the best option because it can absorb some of the moisture. If you use plastic, you may want to drill some drainage holes around the sides so the compost doesn’t get too soggy, and to aerate it. Do not use metal, Styrofoam or any other container that has held chemicals or can leach toxins out into the compost.
The dimensions of the bin are also important. Make sure that the bin is no deeper than 12 inches. You don’t want food wastes to get packed down; this would result in anaerobic conditions and would kill the worms. It would also begin to smell. The width and length of the bin depends on how much food wastes you intend on putting in. I’ve read that for each pound of waste there should be one square foot of surface area.
So, let’s begin the composting! On the bottom of the container, place a layer of moistened bedding material. This can consist of dead leaves, shredded newspapers, scrap paper, saw dust or straw. Anything that has a lot of cellulose and carbon (brown stuff) will work well as a bedding material. It should not be soaked, but damp. The worms will eat this as well as the food. Fill your bin about ½-3/4 of the way full of this material. Fluff it up a bit so the worms have air to breathe; this will also control any rotting smells.
Next, add the worms. According to some studies, redworms can eat their weight in bedding and food wastes in 24 hours. So it is estimated that it takes about two pounds of worms to digest one pound of food in one day. So depending on how much you plan on composting, purchase the amount of worms you think you will need. These worms will also breed and increase in number if conditions are right.
After you add the worms, they will quickly disappear into the bedding because they do not like light. You can now add the food scraps. Push back some of the bedding and bury the waste. The worms prefer this and it will not smell or attract flies. You can add similar organic wastes that you do for a compost pile; fruit and vegetable scraps, coffee grounds, yard clippings, corn stalks, tea bags, etc. Don’t add dairy products or any meat.
Finally, you should cover the pile with a moist burlap or straw. Worms like it dark, and this will facilitate their decomposing activities.
Harvest the compost and worms:
Once the bin is full, it is time separate the worms from the fresh compost and move them to another bin. There are few ways to do this. One fun way is to separate them all by hand but this can take a while; especially if you have two pounds of worms.
An easier way is to push the finished compost and worms to one side of the container, then add new bedding and food wastes to the other side. The worms will gravitate to the other side where there is food, and you can remove the finished organic matter.
Another way is to build a sifter. Make a wooden frame from 2 x 4s and place a 3/16 inch mesh inside. Put some of the compost on top then sift the soil through, leaving the worms on top.
There are also some specialized types of vermicomposting bins that make harvesting easy. The continuous vertical flow design has bins or ‘trays’ stacked on top of each other. Each tray has a chicken wire bottom so the worms can move from tray to tray. The bottom tray is filled like the above description, but when it is full, it is not emptied. Instead, another layer of bedding and food waste is added to the above tray. So when the worms are finished feeding on the bottom bin, they migrate up through the chicken wire to feed on the new food. When most of the worms are in the top tray, the bottom can be harvested. For continuous vertical composting bins, check out worm composting bins at Compost Mania.
Another type of vermicompost bin is the continuous horizontal flow design. This is similar to the vertical flow trays, but the worms migrate horizontally instead of vertically. Chicken wire separates a larger bin in half. When one side is almost finished, fill the other side with bedding and food scraps. Like before, the worms will migrate through the chicken wire to the other side, and you can harvest the finished compost.
I ran into this article at www.thedarkgreenerside.wordpress.com, and was impressed by what worm compost can do:
In the above picture, the plants to the left had no worm compost added, the plants in the middle had 11% worm composting added, and the plants to the right had 21% worm composted added. You can see the results!
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Dickerson, G. (2004), “Vermicomposting”. Cooperative Extension Services, Collage of Agriculture and Home Economics. http://aces.nmsu.edu/pubs/_h/h-164.pdf
Dunn, C. (2007), “Vermicomposting and Vermiculture: Worms, Bins and How To Get Started” http://www.treehugger.com/green-food/vermicomposting-and-vermiculture-worms-bins-and-how-to-get-started.html