Worm Composting (Vermiculture)
How does worm composting differ from traditional composting?
There are three main concerns when starting a vermiculture system - the container, the bedding, and the worms.
There is no textbook description of a container for use in vermiculture. Typically, the containers are construcuted of wood or plastic. Wood offers the advantage of being more absorbent, while plastic containers offer indoor composters the assurance of a self-contained system. See our guide to traditional composting for more information on containers.
The big question when it comes to container is size. How do you know how big of a container is right for you and your waste? As a general rule, your vermiculture bin should allow for approximately one square foot of surface area for every pound of waste to be composted. Containers are typically between 8 to 12 inches in depth.
Next, your container will need ventilation. This is most easily accomplished by drilling 8 to 12 holes in the bottom of the container. The exact number will depend on the type and size of container you use. Plastic containers, in particular, usually require more holes, as they are not porous like wood containers. The key is that your compost should be moist, but not overly damp. And of course, you'll need to place your container above a runoff tray, particularly if working indoors.
Finally, your container will require a lid. For outdoor vermiculture containers, a solid lid is preferred, to keep out animals and the elements. Indoor lids can be constructed of a dark-colored plastic or burlap. The important thing is that your worms have a dark environment with sufficient ventilation. A loosely sealed lid, in combination with the aforementioned drainage holes, should provide plenty of air for your red wigglers.
2. The Bedding
The bedding is the raw material upon with your vermiculture system is based. It provides a "home" for your worms, and a damp environment in which to bury your food waste. A wide variety of bedding materials can be used, including sawdust, cardboard, shredded newspaper, chopped straw, dead plant material, or compost. In general, you should aim to use a variety of materials for bedding, so as to provide a range of nutrients for your worms. A few handfuls of sand or soil are also imperative, to help with essential digestion processes that occur in the worms. In total, your bedding material should fill the container about three-fourths of the way.
As mentioned above, it is important to keep your bedding materials (especially the dry ones) moist. Apply enough water so that the mixture feels like wrung-out sponge to the touch. Then, lift the bedding material carefully to create pockets of air. This helps to control odors and aids in ventilation.
3. The Worms
Last, but certainly not least, are the worms. Two types of earthworms can be used in vermiculture: Eisenia foetida (common name, red wiggler) and Lumbricus rubellus (found in aged manure and compost heaps). So-called dew-worms, the worms commonly found in soil and compost, are not well-suited for vermiculture, and will most likely die.
The more daring composters out there can obtain their worms at the source - in a horse stable or other location where aged manure and compost abound. Otherwise, these worms can be purchased at most bait shops.
The next big question is, how many? Again there are no hard and fast rules, but generally speaking, your worms should have a net weight that doubles the weight of your daily input of food waste. So, for every pound of food waste you put in your container each day, you should provide approximately two pounds of red wigglers. The nice thing about earthworms is that they reproduce quite rapidly. So if you can't get your hands on the weight you need, start with a smaller amount of worms (and a smaller amount of food) and wait for the population to increase.
Feeding Your Red Wigglers
You can include the scraps of most food in your vermiculture bin, including the peels of most fruits and vegetables, coffee grounds, tea bags, and crushed egg shells. Avoid composting meat scraps, oily foods, as well as dairy products and grains, as these tend to attract flies and rodents.
When placing scraps into your bin, be sure to bury them. Scraps left on the surface can attract flies, which can in turn produce odors. Simply lift the top layer of bedding and place your items underneath. It's a good idea to vary the location of burial, as well.
We saved the best part for last. Beyond making sure that you have the proper food-to-worm ratio, very little maintenance is required. After a period of 8 to 10 weeks has passed, you will notice that most of the original bedding material as disappeared. In its place, you will find a rich and earthy layer of worm castings, which comprise the bulk of the compost. A good way to tell when you've reached these point is by looking at the volume of your material. Compost tends to take up much less room than bedding material, so you can expect the overall level of your compost to have decreased significantly.
Using the Compost
When your compost is ready to be removed, be careful not to disturb the red wigglers or their egg-shaped cocoons, which house baby worms. The easiest way to accomplish this is to remove the finished compost one half at a time. Move the worms and their babies to one side of the vermiculture, remove the compost, insert new bedding, and gently replace the worms. Repeat for the other side. It's that simple!
Once you have removed your compost, you're ready to begin using it to enrich the soil of your plants, both housplants and outdoor varieties. It can even be used to lightly coat your lawn. Worm composting is an excellent way to reuse your food wastes, and to promote further plant growth in the process!