Jennifer Schultz Nelson
Extension Educator, Horticulture
If you are a connoisseur of compost, you are probably familiar with vermicomposting, or composting using worms. Vermicomposting, like "regular" composting, can be as simple or as complex as you want it to be. No matter what degree of complexity you prefer, every system has one common goal: to convert food wastes into usable compost for the garden.
A man named Marcus Cato, who was a Roman Statesman, recorded the first use of vermicomposting more than 2,000 years ago. More than one hundred years ago, Charles Darwin found that redworms consume their own weight in organic matter in one day.
There are a few features that every vermicomposting system needs to be successful. The choice of worms is critical no matter what system chosen. There are over 4000 species of worms and all species are not created equal.
There are worms that primarily live deep below the soil surface, such as nightcrawlers, that rely on extensive tunnel systems for survival. Some live as much as three meters (approximately 9-10 feet) below the surface. Their tunneling improves soil structure by aeration, or creating air spaces, which helps loosen tightly compacted soil. These are not the right worms to use for vermicomposting. A vermicomposting system will become far too warm for them, and they cannot make the deep tunnels they prefer within the confines of a typical vermicomposting system.
There are worms that prefer the warm surface organic layers of soil, and are referred to as litter dwellers. The species most recommended for vermicomposting is Eisenia fetida, commonly known as the Red Wiggler. They are also known as the Tiger Worm, Manure Worm, or Compost Worm. They love organic wastes such as kitchen scraps, and the vermicomposting system is the perfect environment for them, mimicking their warm home in the first few inches of soil.
Another feature that all vermicompost bins need is darkness. Red Wigglers prefer the dark. Many materials are suitable to construct such a bin. Wood, opaque plastic, Styrofoam, and metal may all be suitable. The choice of material and design is where the main differences in vermicomposting systems arise.
The bin must be big enough to house bedding material such as newspaper or leaves, plus the anticipated kitchen wastes. Many plans for home-built bins are available in print and online, plus numerous ready-made systems are available. All have advantages, depending on where and how the system will be used. I was very impressed with my friend's system, which she housed in her basement. It took up very little space, and did not smell bad. I opened it and got up close, and it smelled like freshly tilled garden soil.
The wastes the Red Wigglers produce are commonly called worm castings. They are very beneficial for improving garden soil because they are high in organic matter, which will help loosen clay soil, and improve water retention in sandy soil. With a typical kitchen waste diet, castings are relatively low in nitrogen, so there is little risk of burning plants by applying worm castings.
You may not think that this type of system would have much of an effect on reducing wastes shipped to landfills. Think again. The U.S. Census Bureau estimated Decatur's population at 79,285 residing in 34,086 households in 2003. The Environmental Protection Agency (EPA) estimates each person generates 7.2 ounces of food waste each day. That is 35,678 pounds (17.8 tons) of food waste produced each day, and 6,511 tons each year in Decatur!
An average size worm bin containing two pounds of red wigglers can consume about one pound of food waste per day. Based on 34,086 households, if just 5% of them had one of these average worm bins, they could prevent 1,704 pounds (0.85 tons) of food waste from entering the landfill each day, and 622,609 pounds (311 tons) from entering the landfill each year.
You may think vermicomposting is only suitable for home settings-- the IKEA store in Schaumberg, Illinois is proving it can be done in a commercial setting. They recently received state funds to hire New Horizon Organics to construct two mobile vermicomposting units to assess their effectiveness on a large scale. Each unit contains two worm beds, each 3 feet by 20-22 feet. Food scraps from the store cafeteria are fed to the worms daily. The goal is to increase the store's overall recycling rate from 70% to 90% of all waste with the addition of the vermicomposting units.
For more fun worm facts and directions for building your own vermicomposting bin, check out U of I Extension's "Adventures of Herman" the worm at http://www.urbanext.uiuc.edu/worms/ .