MDEQ Composting Program
What is vermi-composting?

Vermi-composting is the process of composting using earthworms. The process functions best when red worms, also known as “red wigglers”, are used to process the waste materials. Night crawlers are not good worms for vermi-composting. Vermi-composting is often faster, more complete, creates a rich organic material and provides for a good supply of worms for fishing.

Where can I get a worm bin?

Go to the Worm Digest website for information on places companies that sell worm bins. Alternatively, build your own worm bin. The rule of thumb for the size of the container is one square foot of surface area per pound of waste food. Purchase a solid or opaque colored plastic container that is rectangular in shape and about 12 to 15 inches in depth. The container needs to have a top. Translucent containers are not recommended since worms do not like light. Drill 1/8″ diameter air holes in the top and sides of the container to ensure oxygen is readily available. These holes should be about three to four inches apart. Holes in the sides of the container should start around four inches from the bottom of the bin. Holes drilled in the bottom of the container can help with drainage. If this is done, a tray under the container will need to be provided to catch the excess moisture. The larger the container that is used, the more waste material will be needed for composting.

A worm bin can also be constructed from wood or can be purchased from a variety of mail order catalogs that sell garden supplies.

How do I prepare the bin for the worms?

Worms thrive in a damp environment but do not like conditions where it is extremely moist or wet and puddling. This will result in odors and worms exiting the box.

Worms need bedding to keep them happy. There are many types of high carbon bedding that can work, but the most often used type is shredded newspaper, napkins, paper bags, fall leaves, or peat moss. Peat moss alone is too acidic and should be mixed with other materials listed above. The bedding should be as damp as a wrung out sponge.

Next, mix in several handfuls of soil with the bedding. The bin should be about three quarters full of bedding and soil.

Finally, add the worms to the bin and start composting.

Where can I get worms?

Go to the Worm Digest website for information on places that sell worms. The easiest and fastest way to get worms is to go to the nearest bait shop and request two to three pounds of red worms or red wigglers. Red wigglers can also be purchased on the Internet from various garden supply companies. The suggested ratio of worms to food should be: one pound per day of food waste to two pounds of worms.

Red wigglers are very prolific. It takes two or three weeks for fertilized eggs to develop in a cocoon from which two or more young worms can hatch. In three months there will be worms sexually mature to start breeding. In less than a year there will be worms available to give to friends to start their on worm bins.

What do I feed the worms?

Red worms can eat over half their weight in food each day so it is important to feed them the correct items. Worms like most organic waste, but will not eat anything inorganic such as plastics. Since redworm do not have teeth and their mouths are small, cut up the food waste so it will be easier to take in. Add soil to the compost bin so the worms can use the grit in the soil to help grind the food in their gizzard.

Food Worms Like
Food Worms Dislike
  • Apples
  • Kiwi Fruit
  • Animal Feed
  • Artichokes
  • Lettuce
  • Dairy Products
  • Bananas
  • Molasses
  • Grass Clippings
  • Beans
  • Oatmeal
  • Manure – Cat, Dog or Horse
  • Beets
  • Onions
  • Meats
  • Bran
  • Pancakes/Waffles
  • Oily Foods
  • Bread
  • Honeydew
  • Potato Chips
  • Broccoli
  • Papaya
  • Salted Peanuts
  • Cabbage
  • Pasta
  • Salted Products in General
  • Cantaloupe
  • Pears
  • Carrots
  • Peas
  • Celery
  • Peaches
  • Cereal
  • Potatoes
  • Citrus Fruit
  • Raisins
  • Coffee Grounds
  • Rice
  • Coffee Filters
  • Spinach
  • Corn Meal
  • Tea Bags
  • Cucumber
  • Tomatoes
  • Eggs
  • Turnips
  • Egg Shells
  • Watermelon
  • Grapes
  • Zucchini
  • Grits

Bury the food items completely under the bedding so they are not visible from the surface. This prevents odors and fruit flies. Do not add more food than the worms can eat in several days. It is very important to understand that worms cannot eat food unless it has already started to decompose. Fresh food waste placed in the bin cannot be readily eaten until several days have gone by. Start slow so the worms are not overwhelmed with food.

Can the worm bin be put outside?

Worms like a warm environment. Temperatures from 45 to 80 degrees Fahrenheit are good. Temperature less than 45 degrees will require for the worms to be brought inside. Basements or garages that don’t freeze and stay reasonably warm are good locations.

What are the common problems and pest issues?

The more common problems associated with a worm bin are unpleasant odors, and fruit flies. The odors can generally be avoided by not overloading the bin with too much food. Start slow and slowly increase the quantities of food that is added to the bin. Lack of oxygen can also lead to odor problems. Simply make sure there are plenty of holes drilled into the bin and from time to time check to make sure they are not blocked. Fruit flies can be kept to a minimum by not overfeeding the worms and keeping the bin covered tightly. In addition, place a solid sheet of newspaper over the bedding and food waste to prevent the fruit flies from getting to the buried food waste. This folded sheet of newspaper can be several layers thick and can be removed each time you bury fresh food waste and then placed back over the material. Worms will also provide warnings that problems exist in the bin. If they begin climbing onto the sides of the bin it is an indicator that the soil conditions are too wet, or the bedding is too acidic. Simply stop placing wet food in the bin for a short time until conditions improve, add more dry bedding or temporarily stop placing acidic citrus fruits in the bin.

How and when do I harvest the finished compost?

Click on City Farmer to view a great method for harvesting worms and finished compost. Red worms create a rich compost known as castings. Finished compost can occur in as little as two or three months. In several months there will be a noticeable difference in the bin. The original bedding should no longer be recognizable and the volume of materials placed in the bin originally should be substantially less.
To harvest the compost, follow these steps. 1) Move the finished compost over to one side of the bin and place fresh bedding and food in the vacant area. In two or three weeks the worms will gradually move from the finished side to the new bedding area in search of new food. 2) The finished compost which the worms have not vacated can then be scooped out and used in the yard or garden. Also, look for the tiny lemon-shaped worm cocoons which contain baby worms! These cocoons can be placed into the new bedding so that there will be more worms to eat the food waste or place them in the garden to begin populating the garden with more earthworms to enrich the soil.