Agriculture Reference
In-Depth Information
Worm Composting
Compost made by worms is called vermicompost. The finished product consists of their
manure (castings) and some decayed organic matter. I've been making it for a few years, or
I should say the red wiggler worms in my bin have been making it — I've just supplied
some food, water and bedding. Of course, billions of microbes and hundreds of other small
insects help them out. Vermicompost is a nice way to recycle your food scraps into beauti-
ful compost. The worms dine on the food scraps largely to get the microbes covering the
surface.
Unlike outdoor composting, this method definitely needs a bin to house the worms. I use
a plastic storage container that's approximately 18 inches wide, 24 inches long, and 12
inches high, with a lid. This size easily allows for the four to five pounds of food scraps I
need composted each week, perfect for two people. A wood box would be nice, too. To
make your bin, drill 12 holes approximately ½ inch in diameter in the bottom and at least
as many holes towards the top of the sides. Some people also like to drill holes in the lid.
The holes allow for air and water vapor exchange, with the bottom holes also facilitating
drainage. You'll need something underneath the bin to catch the water that drains out.
Another upside-down lid is often the perfect size for this.
I don't need to go into much detail here on the materials, because they're basically the
same as a regular compost pile. I don't use meat, dairy or oil, and the worms also don't like
too much citrus or salty food. Since your food scraps are your nitrogen materials, you'll
need to supply some other forms of carbon materials as bedding. I use a mixture of shred-
ded newspaper, leaves and straw. A handful of sand (or soil containing sand) is also needed
for the worms to be able to digest food properly. Most resources recommend adding lime to
increase the pH. We've learned how that is incorrect reasoning, but I do believe ⅓ cup of
calcitic lime per cubic foot of compost will probably be helpful for the calcium, just as it is
in an outdoor compost pile. You can also add any of the activators outlined in the other
composting chapters.
Just like a compost pile, your bin needs to have proper air, moisture, temperature and
carbon to nitrogen ratio. The holes bring in air. You may want to raise the bin slightly off
the ground to increase air flow through those bottom holes. While shredding the bedding
materials is nice for the worms, leaving some of them more coarse will help avoid com-
pressed, anaerobic conditions. The bedding should be wetter than a compost pile — at
about 70-90% moisture. Basically, you want it very moist, but not waterlogged because the
worms still need oxygen. It takes about three times as much water as bedding to get it moist
enough. The temperature should be between 60F and 80F, out of direct sunlight. Just like
an outdoor compost, if the bin is smelly or attracting fruit flies, it's time to add some car-
bon and perhaps stop adding food scraps for awhile.
