Worm Composting
Each year in NC, we landfill over 420,000 tons of food waste. This wasteful practice is costly to both
taxpayers and the environment. Instead of discarding food scraps, recycle them with the help of worms.
Worm composting transforms kitchen wastes and newspaper into a soil amendment that enhances soil
structure and drainage. Worm compost also helps boost the nutrients available to plants, which creates
bigger blooms and produce.
Using worms to decompose food waste:
• Reduces household garbage disposal costs
• Produces less odor and attracts fewer pests than putting food wastes into a garbage container
• Keeps hard-to-process organic waste out of the landfill, reducing cost to taxpayers
• Saves the water and electricity that kitchen sink garbage disposal units consume
• Produces a free, high-quality soil amendment for the garden
• Requires little space, labor, or maintenance
• Provides worms for fishing and pet food
• Is a lot of fun, and puts you in control of turning waste into valuable resources right at home
Equipment and Supplies
The materials needed to start worm composting are simple and inexpensive. All you need is a worm bin,
worms, water, bedding (like newspaper) and your food scraps.
Worm Bin
You can make an inexpensive bin from a 16-gallon plastic tote. This is a low cost and proven way to get
started in worm raising. For two people (producing approximately 3 1/2 pounds of food scrap per week),
a single tote bin is adequate, although some households prefer to have two ormore. Red worms (the type
used for worm composting) thrive in moist bedding in a bin with air holes on all sides. Keep a lid on the
bin, as worms like to work in the dark. Keep the worm bin where the temperature ranges between 55 and
77F. Worms can’t handle freezing or the direct summer sun. The garage is ideal, or out on a shady patio or
porch in the warm months.
More about the worms
Worm composting uses a special “composting’” worm, the red worm or “red wiggler” ( Eisenia fetida).
Beginning worm farmers get their starterworms from friends, bait shops, nurseries, or by mail from
commercial worm growers. Commercial growers are the most reliable and economical source of good
healthy worms. Check the yellow pages or the internet for vendors. These worms will keep reproducing
– fast! There are about 1000 worms in a pound, and soon you’ll have more than 2000. Take a look under
“Harvesting” section for suggestions on how to manage your expanding herd.
Bedding
The worms need bedding material in which to burrow, to bury the garbage, and to hold moisture.
Bedding should be a non-toxic, fluffy material that holds moisture and allows air to circulate.Suitable
materials include shredded paper (such as black-and-white newspapers, paper bags, computer paper,
or cardboard); composted animal manure (cow, horse, or rabbit); shredded, decaying leaves; peat moss
(which increases moisture retention); or any combination of these. Do not use glossy paper or magazines.
Worms will eat the bedding, so you will need to add more within a few months. The worms need bedding
material in which to burrow, to bury the garbage, and to hold moisture. Bedding should be a non-toxic,
fluffy material that holds moisture and allows air to circulate.Suitable materials include shredded paper
(such as black-and-white newspapers, paper bags, computer paper, or cardboard); composted animal
manure (cow, horse, or rabbit); shredded, decaying leaves; peat moss (which increases moisture
retention); or any combination of these. Do not use glossy paper or magazines. Worms will eat the
bedding, so you will need to add more within a few months.
Food Scraps
Feed your worms any non-meat organic waste such as vegetables, fruits, eggshells, tea bags, coffee
grounds, paper, coffee filters, and shredded garden waste. Worms especially like cantaloupe, watermelon,
and pumpkin. Limit the amount of citrus fruits to prevent the bedding from becoming too acidic. Break or
cut food scraps into small pieces. Do not add meat scraps or bones, fish, greasy or oily foods, fat, tobacco,
or pet or human manure.
Be sure to cover the food scraps completely with the bedding to discourage fruit flies and molds. One
pound of worms will eat about three and one half pounds of food scraps a week. If you add more food
than your worms can handle, anaerobic conditions will set in and cause odor. This should dissipate shortly
if you stop adding food for a while.
Practical hints
Before set up, decided where you’ll put your worm bin. Popular indoor spots are the kitchen, pantry,
bathroom, mudroom, laundry room, or basement. If you want to keep your worm bin outside, put it in
theshade during the hot summer. Shelter it from the cold in winter by placing it in a garage or carport, or
by putting hay bales around the bin to allow aircirculation while blocking cold and wind. Always protect
the bin from flooding, because the worms can drown.
Making the bedding: If you want to use newspapers, fold a section in half and tear off long, inch wide
strips (go with the grain of the paper and it will tear neatly and easily). Soak the newspaper in water for
several minutes, one half hour maximum, then wring it out gently. Fluff up the newspaper as you add it
to your worm bin. The bedding should be very damp, but not soaking wet (only two to three drops of
water should come out when you squeeze the bedding material). Spread the bedding evenly until it fills
about three-quarters of the bin. Sprinkle a couple of handfuls of soil (from outdoors or potting soil) into
the bedding to introduce beneficial microorganisms and aid the worms’ digestive process. Some
experienced wormers like to fluff up the bedding about once a week so the worms can get plenty of
air and freedom of movement-others believe in a policy of strict non-interference.
Settling in: Gently place your worms on top of the bedding. Leave the bin lid off for a while so the worms
will burrow into the bedding, away from the light. The worms will not try to crawl out of the bin if there
is light overhead. Once the worms have settled into their new home, add food scraps that you have been
collecting in a leak-proof container. Dig a hole in the bedding (or pull the bedding aside), place the food
scraps in the hole, and cover it with at least an inch of bedding. After this first feeding, wait a week
before adding more food. Leave your worms alone duringthis time to allow them to get used to their
new surroundings. Bury food scraps in a different area of the bin each time. Worms are always hungry,
so you can feed them any time, day or night.
Other critters
Do not be surprised to see other creatures inyour worm bin, as they help break down the organic
material. Most of the organisms will be too small to see, but you may spot white worms, springtails,
pill bugs, molds, and mites.
Harvesting the Worms and Compost
After about six weeks, you will begin to see worm castings (soil-like material that has moved through the
worms’ digestive tracts). In three or four months, it will be time to harvest the castings. The mix of castings
and partially decomposed bedding and food scraps, along with the worms themselves, is called
vermicompost. Most home worm farmers harvest and use vermicompost instead of “pure” castings.
Vermicompost is much easier to harvest and gives many if not all of the same benefits in the garden.
There are different ways to handle harvesting:
Simple
You can remove about half of the worm castings and put that on the garden, worms and all. Red worms will
not generally survive long in garden soil, but do no harm (if you have deep organic mulch, some worms may
survive for a considerable period). Add fresh bedding to the remaining vermicompost to refill the bin. The
cocoons and worms in the castings will quickly recolonize the bin.
Recycling the worms
Place food scraps on only one side of your worm bin for several weeks. Most of the worms will migrate to
that side of the bin. Remove the vermicompost from the other side of the bin where you have not been
adding food scraps, and add fresh bedding. Repeat this process on the opposite side of the bin. After you
have harvested both sides, begin adding food scraps to both sides of the bin again. Some commercial
composters, like the “Can’O’Worms,” use a more complex version of this technique.
Sorting worms
This is the best technique if you want to harvest worms for sale, fishing or sharing with friends. Experiments
with worms often require careful sorting and counting as well. Empty the contents of your worm bin onto a
plastic sheet or used shower curtain where there is strong sunlight or artificial light. Wait 20-30 minutes, then
scrape off the top layer of vermicompost. The worms will keep moving away from the light, so you can scrape
more compost off every 20 minutes or so. After several scrapings, you will find worms in clusters; just pick
up the worms and gently return them to the bin in fresh bedding. Be on the lookout for worm eggs; they are
lemon shaped and about the size of a match head, with a shiny appearance, and light-brownish color. The
eggs contain between two and twenty baby worms. Although it is time consuming, you may want to return
the eggs to your bin so they can hatch and thrive.
Using Worm Compost
Use your vermicompost immediately or store it and use it later. Mix it into the top six inches of soil in your
garden and around your trees and yard plants. You can also use it as a top dressing on outdoor plants or
sprinkle it on your lawn as a conditioner. Vermicompost makes a great nutrient-rich mulch. For indoor plants,
mix vermicompost with pottingsoil. For top dressing indoor plants, remove any unsightly decaying bedding
and food scraps from the castings (most of the castings themselves will be black, crumbly and have a faint
pleasantly earthy smell). Remove worms and eggs, which cannot survive in an indoor pot. You can also make
a “compost tea” to feed to your plants. An easy recipe is to add two tablespoons of vermicompost to one
quart of water and allow it to steep for a day, mixing occasionally. Water your plants with this “tea” to give
them a boost.
Large-Scale Vermicomposting
Wherever human activities generate food scraps or organic wastes, vermicomposting can transform ‘garbage’
into a valuable resource. Worm composting bins have a place in classrooms, apartments, offices, and other
commercial locations. Large-scale worm farms exist in many states, including California, New York, Rhode
Island, Washington, and Oregon, as well as right here in the Carolinas. Vermicomposting is even helping
to solve North Carolina’s hog waste problems. Classrooms and outdoor centers are especially appealing
settings for worm composting. Children of all ages enjoy classroom activities involving worms. Several
curricula on worms are available for classroom use, and teachers and parents can use worms in a multitude of disciplines, including science, mathematics, geography, language arts (vocabulary, poetry, and
prose), and
even music.
Sources of Additional Information and Supplies
Worms Eat My Garbage by Mary Appelhof.
North Carolina Cooperative Extension Service Department of Biological & Agricultural Engineering,
North Carolina State University, Box 7625 Raleigh, NC 27695-7625