Our Friends, The Worms
Before I got into vermicomposting, I was of the opinion that a worm is a worm is a worm…they’re all little slimy legless things that live in the earth, and that’s that. This is sort like thinking that a bird is a bird is a bird is a bird…they all have wings and flap around in the air, right? Of course, anyone who has seen a hummingbird and a penguin and a vulture knows that while they may all be birds, there are significant differences in how they live their lives.
One way to classify earthworms is by the environments they live in, and by the habits associated with these environments.
The worms that do best in compost systems are classified as epigeic, that is, they reside on the surface of the earth (“epi” suggesting “on” or “upon,” and “ge(o)” suggesting “earth”). These types of worms feed on leaf litter in the wild and tend not to burrow deep into the ground. The species that are generally sold as compost worms, including Eisenia fetida, Eisenia andrei, and Eisenia veneta do well in relatively warm temperatures(55°F-85°F), can eat a lot of organic matter (estimates range from 25% to 50% of their body weight daily), and reproduce relatively quickly.
Setting Up a Worm-Friendly Environment
Once you’ve found a container to house your vermicompost system, you’ll need to create an environment your worms will thrive in. Sometimes I hear folks talk about adding soil to a worm bin. Intuitively, this makes sense, since we tend to think of earthworms as living in the earth, but, as I mentioned earlier, the worms you’ll want to use in your system aren’t really soil-dwellers. A bunch of soil in your bin will probably just end up making the bin heavier than it needs to be, so I think that this is an unnecessary addition. That being said, a handful of sand can provide the grit that helps the worms grind food in their gizzards.
The bulk of your bin should be occupied by moist bedding. Bedding serves a similar structural function to the “browns” we talked about in outdoor composting–it regulates moisture within the system, creates air pockets, and when applied in a thick layer on top of the feedstocks, can thwart potential pests. The bedding that is probably most commonly used in home vermicompost systems is shredded paper (not the glossy kind, and, ideally, with a minimum of colored ink), but a variety of high-carbon materials, including cardboard, dried leaves, straw, or wood chips will also work.
When you’re first setting up your bin, it’s a good idea to moisten your bedding with water; you’ll want it to have a wetness similar to that of a wrung-out sponge. This is a good level of moisture to strive for in the system as a whole; I find that once my systems have been operating for awhile, the feedstocks I add tend to create an environment that is a little too wet, so I make sure to add plenty of bedding on top of each food scrap deposit to ensure that things don’t get too soupy and anaerobic. You’ll want to make sure the surface of your system is covered with several inches of bedding at all times to minimize fly and odor problems.
One more thing to consider when setting up a system: you’ll need to pay a little more attention to your feedstocks in the beginning than you will once a stable little ecosystem has established itself. I would start out by adding relatively small amounts of finely chopped food. Worms don’t have teeth, so adding food that has a lot of surface area will ensure that they can access the food more quickly. Also, it’s best to stay away from salty or acidic foods. If you’re starting out with about a pound of worms in your system, try adding a quarter pound of chopped fruit and vegetable peels, wait a couple days, and add more as needed.