What Is Composting with Worms?
Composting with worms, commonly known as vermicomposting, typically involves the use of the common red wiggler worm (Eisenia fetida). This worm’s specialized digestive system converts food waste and other organic materials into nutrient-rich compost called vermicast or worm castings. It thrives in an aerobic (air-containing) environment, efficiently processing large amounts of food waste while reproducing rapidly in a confined space.
Difference Between Conventional Composting and Vermicomposting
Conventional or “hot” composting relies on the heat generated by a variety of microorganisms, primarily bacteria, to convert organic waste into compost. Factors such as the carbon-to-nitrogen ratio of the composting materials, moisture levels, and air circulation contribute to producing heat, which promotes composting and kills weed seeds. When performed correctly, this process takes about six to eight weeks under optimal conditions.
Vermicomposting, on the other hand, is a “cold” composting process. This method does not generate noticeable heat through bacterial activity during decomposition. Vermicomposting materials, which include food scraps and bedding, typically have a lower carbon-to-nitrogen ratio compared to hot compost. Instead of relying on heat, this process depends on various micro- and macroorganisms, including worms. The process can take up to six months to yield finished worm compost and does not destroy weed seeds. However, it can provide up to 4% more nitrogen in the final compost than conventional hot compost. Vermicomposting can also be done inexpensively, in a small space, with minimal effort.
Why Should I Vermicompost?
In the United States, most food waste ends up in landfills, constituting 20% (by weight) of all landfill materials. When this food decomposes in a landfill, it generates methane gas, a potent greenhouse gas that traps heat in the atmosphere. Methane is about 20 times more effective than carbon dioxide regarding its warming potential.
By recycling organic waste through vermicomposting, we can divert waste from landfills. This process proves easier than conventional composting, which requires regular turning and managing complex ratios of materials. Vermicomposting suits individuals without space for a regular compost bin, such as apartment dwellers. Additionally, vermicast enriches the soil with beneficial microorganisms and nutrients, including beneficial bacteria, fungi, and protozoa, as well as nitrogen, phosphorus, potassium, calcium, and magnesium.
Materials Needed for Vermicomposting
To ensure a successful vermicomposting setup, gather the following materials:
- A ventilated container with drainage (worm bin)
- Red worms
- Biodegradable bedding
- Some form of grit
- A food source, such as kitchen scraps
- Water
Choosing a Location for the Worm Bin
Indoors
A well-tended worm bin remains odorless. You can keep it in a pantry, utility room, or under the kitchen sink. A garage, basement, or carport also serves as a potential site. Avoid placing the bin in areas with heavy foot traffic or near washers and dryers, as vibrations may encourage the worms to escape.
Outdoors
Worms thrive in temperatures between 55°F and 77°F. If you keep your bin outside, protect it from extreme temperatures. The north side of a structure (such as a house, shed, or garage) is preferred because it maintains more stable temperatures. Additionally, provide protection from rain and wind by placing it under the eaves, a deck, or building a cover that repels rain while allowing good air circulation. An outdoor bin must also be secured against rodents, raccoons, and other animals.
Depending on your local climate, you may place your worm bin outside during warmer months and bring it under cover during cooler months. Choose a location that you visit often!
Determining Worm Bin Size
To figure out the bin size you need, first determine how much food waste your family generates in one week. Your worm bin must contain 1 cubic foot of space for each pound of kitchen waste. This does not mean that the bin will always be full, but rather that it provides ample space for worms to thrive while maintaining the right moisture and oxygen levels.
You’ll need approximately 1 cubic foot of bin space and 1 pound of food waste for each pound of worms you maintain (about 1,000 worms per pound). Following this rule prevents an overloaded or undernourished system. Excess food may lead to overfeeding and harmful anaerobic conditions for the worms. Insufficient food slows the worms’ growth and reproduction and can lead to their demise.
A 14-gallon worm bin measuring 1 foot deep by 1 foot wide by 2 feet long (1′ x 1′ x 2′) provides 2 cubic feet of volume, allowing for 2 to 2½ pounds of worms. A system of this size can process 2 pounds of kitchen waste per week, approximately what an average family of two or three produces. A family of four to six would need a larger bin 6 cubic feet (1′ deep x 2′ wide x 3′ long) and more worms (up to 6 pounds) to process about 6 pounds of kitchen waste per week.
Notice that in both cases, the container depth remains the same. Since red wiggler worms dwell near the soil surface in nature, their survival in a worm bin requires the bin space to be no more than 1 foot deep. This depth ensures healthy aerobic conditions in the worm bin habitat.
Prepare the bin before your worms arrive. Don’t worry if your measurements or methods aren’t exact. The worms will thrive!
Materials for Building a Worm Bin
You can use various materials to build a worm bin. Popular options include plastic totes, wooden bins, and commercial, stackable worm towers. You can also repurpose shipping crates or food storage barrels. Just ensure that the wood has not been treated with chemicals and that other toxic materials haven’t been stored in the containers (food-grade is best).
Characteristics of Wood and Plastic Bins
Wood Bin
- Natural material
- Can be cut to any size
- Breathes, allowing for evaporation during hot weather
- May dry out in extreme heat
- Eventually degrades
- Not easily movable
Plastic Bin
- Durable
- Space efficient
- Needs to drain well
- Retains moisture well
- May become too wet
- Clean and neat
Choosing a Plastic Tote
Most worm bins are made from plastic totes. Worms are sensitive to light, so be sure the container is opaque and has a lid. The lid should fit snugly on the bin to prevent worms from escaping and unwanted pests from getting in. There are many different designs available. You can purchase a premade tote or build your own. The two-plastic-tote bin system is relatively low-cost and easy to make.
To build this system, choose two sturdy, opaque plastic totes (with tops) of the same size (14 gallons is a good size to start with). The first tote is the vermicomposting bin (or worm bin). It nests inside the second tote, which collects any leachate (liquid residue) from the composting process. Note the spacer at the bottom of the second bin. They keep the top bin from sticking and make it easy to lift out. Use plastic for spacers. Wood and bricks are hard to clean.
Drill up to 20 ¼-inch holes in the bottom of the first tote. These holes allow for drainage. If you have commercial vents for air circulation, drill four (or more) 1-inch holes for them along the top edge of the first bin. Otherwise, drill up to 10 ¼-inch holes on the sides, 2 to 3 inches below the lip of the tote, for ventilation. You can drill up to five 1-inch holes fitted with vents on the lid of the vermicomposting bin to aid in air circulation. If you do this, be sure that the bin is not left out in the rain. If you wish, you can install a drain plug on the second bin to make it easier to drain the leachate.
Stacking Tray System
Stacking tray systems are commercially available and operate on the fact that worms follow food. Put bedding and worms in the bottom tray along with food scraps. Once the food scraps are converted to compost, the worms look for a new source of food. Stack a new tray of fresh bedding and food scraps on top of the first tray. The worms wriggle their way through small holes in the bottom of the top tray to get to the food above. You harvest the compost in the first tray and keep stacking new trays on top. Most have a drainage tray at the bottom to collect leachate.
Other Homemade Bins
Probably the most well-known type of worm bin is a wooden box (1 foot deep x 2 feet wide x 3 feet long) with drainage holes drilled in the bottom and a hinged lid for access. Wooden bins breathe and have few odor or excess moisture problems. The main drawback is their weight. Installing wheels on the bottom of wooden bins makes them easier to move.
Suitable construction materials include exterior-grade plywood or construction-grade lumber. Note: The choice of wood is important. Do not use pressure-treated wood for worm bins. The chemicals are toxic to the worms. Wood that contains a natural pest deterrent such as cedar, redwood, or cypress may be toxic to worms.
If you paint the outside of the bin, use a non-toxic sealant. Inside, line the bottom with cardboard, a plastic liner, or a burlap sack to hold in moisture while allowing drainage. You may need to cover the bin with plastic in very hot weather, but make sure that the lid remains ventilated.
