Vermicomposting at McDevitt Middle School

Wiggling around

Squirmin' around

This past month, Healthy Waltham has teamed up with McDevitt Middle School’s 6th grade science Cluster Challenge teachers and students to begin a project that puts worms to work while reducing waste by recycling kitchen scraps. Vermicomposting, or the use of worms to quicken the decomposition process of plant waste, is an easy, inexpensive, and fun garden activity that can be maintained year round in any climate, as long as you don’t mind sharing some of your indoor space with a sealed bin of worms! To get started, all you need are some basic materials for your bin and bedding, a “starter set” of red wigglers or another type of composting worm, and a handful of kitchen scraps for worm food. For more detailed instructions on building your indoor or outdoor bin, we suggest referring to the New Mexico State University Extension Service’s easy-to-follow instructions available here. Below, we’ve outlined some of the key elements for starting an indoor worm bin at home or in the classroom.

Building Your Bin

While there are specially-made worm composting bins available for purchase, it is much less expensive to build your own using materials that might already in your house or classroom. Bins can be made of wood, plastic, or Styrofoam because such materials will not easily decompose but can be punctured for bin aeration and water drainage, helping to ensure the creation of an optimal worm habitat. Below, we’ve listed some general guidelines for indoor bin construction:

  • A bin should have a depth of 8-12 inches max; anything deeper will likely cause bedding to pack down, which can decrease air flow and kill worms
  • The bin should have a cover to keep light out and bugs in (you might find more than worms in your bin, depending on your starting materials)
  • 1/4 – 1/2 inch holes should be made in the sides and bottom of your bin for aeration and water drainage; a bin can be set atop blocks with a pan or second lid below to collect “compost tea,” the nutrient-dense, liquid portion of compost
  • A general rule of thumb: you will need about 1 square-foot per pound of garbage, and about 2,000 breeders (mature worms; about 2 lbs) are needed to consume 1 pound of garbage per day; with some simple calculations, you can figure out the optimal bin size for your waste needs.

Setting up the bedding

Bedding materials might be even easier to find around the home, classroom, and office. Items such as shredded newspaper (soy-ink only!), computer paper, cardboard, dried leaves, grass clippings, and straw all work very well as worm bin bedding; a combination of these items is even better because it prevents the packing of materials and increases the bedding’s (and therefore compost’s) nutrient content. Bedding must remain moist but not waterlogged; optimally, it should feel like a rung-out sponge: damp but not soaked! Keeping a spray bottle of water near your bin is convenient way to maintain adequate moisture. Some sand or soil must also be added to the bin for the worm’s to properly digest their food since they don’t have teeth to chew. Setting up bedding a week prior to moving the worms into their new home helps ensure the bin will not get too hot as it allows heat-producing bacteria to get the decomposition process started.

Purchasing Worms

Greens are good, but leave out the onions!

For vermicomposting, the best way to get worms is through an online farm, garden or worm supplier, such as those listed here. Feel free to check out your local bait & tackle shop, but they might not sell those worm species best-suited for composting, such as brandling worms (Eisenia fetida) or red wigglers (Lumbricus rubellus).

Maintaining Your Bin

Once started, it relatively easy to maintain your indoor bin. Try to keep your habitat at room temperature, within the range of 55-77 degrees F, for optimal breeding and feeding conditions. As previously mentioned, be sure the bin remains adequately moist; check holes in the bin for blockages. Food scraps, such a fruit and vegetable peels and ends, eggshells, teabags and coffee grinds, and oatmeal are all excellent feeding materials. However, you should avoid adding citrus fruit, garlic, onions, and spicy foods to maintain the proper pH (worms don’t like acidity) and never add meat, dairy, or fats as they not only attract flies and animals but also produce really foul odors!

Finished compost in the worm bin

Within 2-3 months, or when you start to notice bedding disappear, you can begin to harvest the finished compost and perhaps start another bin with your growing worm population!

We’ll continue to follow the results of our McDevitt classroom bins as well as some experimental bins maintained at Brandeis University by Healthy Waltham intern Cece Watkins. For more information on worms and the vermicomposting process, stayed tuned.


Information on vermicomposting provided by The Worm Book by Loren Nancarrow and Janet Hogan Taylor and the New Mexico State University Cooperative Extension Service. Images by Rebekah Carter (2011).

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