Vermicomposting Frequently Asked Questions

Vermicomposting is composting with earthworms. It is becoming a popular alternative or addition to composting and has several benefits for home gardeners. Because the earthworms actually eat vegetable and fruit scraps, the scraps are degraded faster than in typical composting systems. Vermicomposting can also be done indoors throughout the winter, whereas typical composting slows or stops during the winter months. 

Vermicomposting is relatively easy. You add kitchen scraps to the system a few times a week. Mist with water, if needed, to keep the earthworms and materials from drying out. And add shredded paper as needed if the environment is too wet. Bins are kept in a dark location as the worms prefer a dark environment. 

If you are thinking of starting vermicomposting at home, below are a few frequently asked questions and answers. 

A sample of vermicomposting worms
A sample of vermicomposting worms.

What type of container should I use for vermicomposting?

You have several options for containers. Multi-layered vermicomposting systems are available from online retailers, but they tend to be expensive. Less expensive options include plastic bins, old drawers, an empty 2-liter bottle, or an empty plastic gallon ice cream bucket. If the bins are to remain outside, they should include drainage holes in the bottom. If the bins come indoors for the winter, no drainage holes are drilled in the bottom and a layer of gravel is placed in the bottom of the container for excess water. Containers should have loose fitting lids that allow for air exchange but prevent worms from escaping and access by other creatures. Air holes can be added to the lid to allow for air circulation.

The size of the container depends on the amount of scraps and the number of worms present in your bin. For one or two-person households with a couple of handfuls of kitchen scraps every few days, the bin can be relatively small – about the size of a large shoe box or a gallon ice cream bucket. A family might have something a bit larger like a 10 or 20 gallon plastic tub.

How do I set up a vermicomposting container?

Once you have identified a container, place a layer of pea-gravel in the bottom to collect moisture. Generally an inch or less is all that is needed. Add a few inches of shredded paper and an inch of potting soil or garden soil. Mist to moisten the material and add the worms and kitchen scraps. Multiple layers of paper and soil are acceptable. The entire depth of the bin can be less than a foot and still function properly. The shredded paper acts as bedding for the worms and as a topper for the system. If moist paper is kept on top there should be fewer problems with fruit flies.    

What type of worms should I use for vermicomposting?

Red wigglers or redworms (Eisenia foetida) are best for home vermicomposting. Red wigglers are available at some local bait shops or online. Nightcrawlers are not preferred because they depend on cooler temperatures and make extensive tunnels that may make the bins an unsuitable environment for long-term success. One pound of worms generally equals 1000 worms. This is plenty of worms for a family size bin.

What should I feed the worms?  What should I avoid adding to the vermicomposting bin?

I tell my students that worms are vegan and therefore should only be fed scraps from fruit and vegetables. No meat, no dairy, no cheese, no bones, no manure, or any other animal product should be added to the vermicomposting bin. Shredded newspaper, copy paper, or even shredded cardboard is beneficial. Avoid adding plant material that has been sprayed with insecticides or other chemicals. Also avoid adding plastic, metal, or other non-biodegradable products.

How do I maintain the worms in the winter?

Red wigglers prefer temperatures between 55-75 degrees Fahrenheit. Most homes maintain these temperatures during the winter months so it is best to bring vermicomposting bins indoors during the winter. Dark locations like a basement corner or under the kitchen sink are ideal. A well-maintained vermicomposting system has little or no odor. Indoors the worms can be continually fed throughout the winter months as they do not go dormant. Ideally vermicomposting systems are not allowed to freeze, as this will kill the worms.

How do I harvest the compost and worm castings?

The worm casting and compost are beneficial additions to garden beds and soil mixes. Finding a way to harvest this material without taking the worms out of the system can be tricky. This usually means moving the worms to lower areas in the bins and harvesting from the top. One way to move the worms lower is to open the bins and place them in a well-lit location for a few hours. The worms will move to the darker and deeper depths so that the top few inches should be free of worms.

In the summer, you can empty the bin on a tarp and separate the worms from the castings and other bedding materials. This is a great opportunity to clean out the bin and place the worms into restored environment with fresh bedding and new scraps. 

For more information on vermicomposting for home gardeners, check out the videos and publications from North Carolina State University at www.composting.ces.ncsu.edu.

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