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Digging Deeper

Vermicompost: Compost for an Urban Farmer

We compost

Authored by Stephanie Price, 2011 Education and Outreach Intern

Compost is a great fertilizer and soil amendment. As a fertilizer it provides additional nutrients for developing plants, and as a soil amendment it improves soil qualities such as water retention and aeration to enhance plant growth. Composting is a complex process at the microscopic level where organic matter from plants and animals is decomposed by organisms such as worms and fungi, and converted to nutrients by aerobic bacteria.  The good news is that it doesn’t take much on our end to reap the benefits of composting. Successful composting takes little effort; it essentially involves compiling wastes and letting the microorganisms get to work!  Composting is a great way to get rid of wastes in an eco-friendly manner.

One draw back to regular composting is that it can require a backyard or other large space.  A great alternative that requires little space is called vermicompost.  Vermicomposting, like regular composting, is a way to convert wastes to nutrients for fertilizing soil. The only difference is that vermicomposting uses certain worm species, in addition to microbes and bacteria, to create this compost. Basically, worms convert your scraps to compost by simply consuming it, letting it travel through their digestive system, and eliminating it as worm castings.

Vermicomposting is easy! To get started, all you need is a bin, bedding, and worms and a basic understanding of feeding and harvesting the compost.

The Bin

The bigger the bin, the better your composting system will work. A good size for starting out is about a 1 ftbin that can be purchased at any local hardware store (for example, a common plastic storage tub- drill holes into the bottom for air circulation). Once you get the hang of composting, you can upgrade to a bin with a larger surface area.

The Bedding

After you have a bin, create bedding for your worms. Bedding should consist of soil in addition to carbon sources. Common materials used include paper products, shredded leaves, peat, and coir. Avoid newspaper, as this contains clay and will become very soggy. Bedding should be kept moist, but not too wet. A good rule is to have bedding that is 60-85% moisture. If needed, occasionally spray the bedding with a water bottle to maintain moisture.

The Worms

There are specific species of worms that work for composting that can be purchased from a variety of retailers. The most common varieties used are the red wiggler (Eisenia foetida) or red earthworms (Lumbricus rubellus).

Feeding the Worms

After putting the worms into the home you created, start slowly feeding the worms by burying your kitchen scraps in addition to dead plants, lawn trimmings, and paper in the bedding. Acceptable food scraps include coffee grounds and filters, tea and tea bags, bread and other grains, ground up egg shells, fruit rind and cores, and small amounts of citrus to maintain a neutral pH. Don’t feed worms any meat, fish, dairy, grease and oils, or pet and human waste. Also be careful to avoid overfeeding worm as this can kill worms and also cause an unpleasant odor. A good rule of thumb is to start slow and only add food when previously added food becomes unrecognizable. It is important to note that worms won’t starve; in fact they can survive up to two weeks without additional food. Besides occasional food, worms require little more attention. Just store them at room temperature in a dark place such as a basement or garage, keep the bedding moist, and aerate the bedding weekly by gently fluffing the soil.

Harvesting the Compost

After following these simple steps, your worms will be ready to work with bacteria and enzymes in the soil to provide you with nutritious compost for your garden! The only additional requirement from you is to harvest the compost. This is also very easy, and can be done by two common methods. One is the light method, which requires shining a bright light on one end of the compost bin. Worms dislike light and will, in theory, move to the other end of the bin so you can then harvest the worm-free compost. The other method is more passive and requires periodic placement of food in different areas of the bin. After placing food in one end to attract worms to that side, compost can then be harvested from the other end.

Vermicomposting may sound daunting, but it really is a fairly simple and affordable way to improve your garden and benefit the planet by reducing waste. It is a great method for any gardener, but especially the urban farmer who has limited space and access to other sources of fertilizer such as manure. There are many great resources available if you are interested in learning more or are ready to get start your vermicomposting adventure!

  • Worms Eat My Garbage by Mary Appelhof
  • Eat More Dirt by Ellen Sandbeck, local author and organic landscaper from Duluth, Minnesota
  • Green Noise, based in Minneapolis, provides workshops and other resources for worm composting through its website
  • Eureka Recycling’s website provides general composting info
  • Several local businesses carry supplies:  Mother Earth Gardens (Mpls), Amelia Flower and Garden Shoppe (Mpls) and EggPlant Urban Farm Supply (St Paul)
  • Worm castings can be purchased at Mill City Farmers Market from vendor Swede Lake Farms
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