Tips for vermicomposting

Vermicomposting, nature’s ultimate recycling system, utilizes a specific type of worm to process large quantities of organic materials. After digesting the edible components, worms produce nutrient-rich remains in the form of worm castings, or vermicompost, an extremely rich form of compost. 

Why we should consider vermicomposting ?

  • Worm compost (castings) can be added to indoor plants as well as outdoor plants as a rich form of plant food.
  • Vermicomposting reduces the amount of garbage produced and sent to the landfill, because food scraps, dry leaves, and newspaper are used in their bedding.
  • Redworms (Eisenia foetida), the type of worm used in worm bins, reproduce rapidly and can be shared with others for starting their own worm bins.
  • Worm bins, when maintained properly, produce little or no odor.
  • Worm bins are small, compact and perfect for apartment dwellers.
  • It is easy to maintain a worm bin than a compost pile, which needs to be turned weekly.
  • Worm bins are an easy way to introduce children to composting and caring for the earth.
  • Worm bins can be kept indoors during the winter and relocated outdoors during frost-free months, thus extending the composting season to year-round.
  • Worms are great pets – they are quiet and you don’t have to walk them!

Making a worm bin when vermicomposting:

  • A worm bin can be started in a 10-gallon Rubbermaid container in a dark color. Around the sides, the bottom, and the top of the Rubbermaid container, drill small holes about 3” apart. This will allow airflow in the bin. You may provide a tray or additional lid for the bottom, to capture any draining liquids.
  • Collect dried leaves for the bedding.
  • Tear up newspaper into small squares to mix with the leaves. Avoid any shiny pages (usually used in advertisement inserts) since the ink used in their processing could be toxic to the worms. Fill the container almost to the top, using equal amounts by volume of leaves and newspaper for the bedding.
  • Cardboard that is free of wax, herbicides, pesticides and bleach may also be used for bedding. Avoid using paperboard, the material typically used for cracker, cereal, and shoe boxes, as it contains waxes and glues that can harm the worms.
  • Add warm water to the leaves and newspaper until the mixture feels like a wrung out sponge. A worm’s body is more than 90% water so it is important to keep the bin moist.
  • Add well-chopped, non-meat food to the bedding, making sure to bury the food about an inch below the surface of the bedding. See below for more information on feeding your worms.
  • After moist bedding and food are in place, it’s time to introduce red wigglers (also known as manure worms or brandling worms to their new home). Avoid using the larger earthworms known as ‘night crawlers’ as they are unsuitable for indoor composting. Worms should be carefully placed on top of the bedding. They will then migrate downwards to escape the light. Finish by covering the bedding and worms with several damp pieces of newspaper to maintain an even level of moisture in the bin.
  • Place the worm bin on a tray or extra lid to collect any moisture that drains through the holes on the bottom on the bin.
  • Collect leaves and newspaper to renew the bedding as it decomposes.

While vermicomposting Maintaining the worm bin:

  • Worms should be fed once a week. Aerate the bedding each week, feed in a different part of box each time, and make sure worms have eaten most of food before feeding again. Do not overfeed the worms.  If you do, you will attract flies and the bin will start to smell. If the worm bin is too wet, add newspaper and leaves. If too dry, add a little bit of water at a time.
  • Worms eat their weight in organic matter each day. One pound of redworms will process one pound of organic matter daily.
  • Keep the worm bin in a cool, dark, dry place as worms do not like light.

Food that is suitable to add to a worm bin while  vermicomposting includes:

  • Vegetable and fruit trimmings as well as the peel
  • Stale bread 
  • Used tea bags and tea leaves
  • Toilet paper or paper towel tubes (make sure there is no glue on the roll) 
  • Newspapers cut into small pieces
  • Vacuum cleaner dust
  • Coffee grounds and filters 
  • Crushed eggshells (helps with worm digestion)
  • Cardboard, plain and corrugated (no shiny cardboard or paperboard)
  • Avocados (worms love avocados)
  • Dried leaves 

 Food unsuitable for worm bins include:

  • Citrus fruits 
  • Meat, including chicken or fish
  • Bones
  • Glossy paper (like magazines and shiny newspaper inserts)  
  • Salt
  • Spicy vegetables (onions, hot peppers)
  • Sawdust 
  • Dairy products
  • Garden weeds 
  • Potato peels and sweet potato peels (could sprout in the worm bin)
  • Fruit seeds
  • Junk food (chips, candy, etc.) 

Harvesting the castings:

Vermicompost is usually produced in two to three months. Worm castings look and feel like dark, moist, forest-scented soil. When the worm bin is entirely filled with dark, moist compost, it is time to remove the vermicompost from the bin and set up new bedding for the worms to start over. Remove the worms either by hand or sift out into another container.

This resource was prepared by Yvonne Greenbaum and Carol Murphy, Denver Urban Gardens Master Composters.

Also see:

Where to Find Worms
Composting Basics
Free Public Composting Classes
Master Composter Training Program