Vermicompost is composting with the use of special earthworms. Red wigglers and white worms are the more common worms used, although European night crawlers can be used as well. Red wigglers can be found living in manure piles and in rotting vegetation and adapt the best in covered worm bins. Common earthworms burrow deeply and are not recommended for use in compost bins. Blue worms are commonly used in the tropics.

Worms are used to decompose vegetable and food waste along with bedding materials into a usable byproduct known as vermicast or worm castings. Vermicast is a dark organic material with a high concentration of nutrients along with water-soluble nutrients and lower levels of contaminants which is used as fertilizer. The act of making Vermicompost is known as Vermicomposting.


Fertilizer – Vermicompost is sown directly into the soil or used to make worm tea. Worm tea is where vermicompost is mixed with water and then oxygen is added with a small aquarium air pump. This tea will need to steep for several hours or days. The tea is then diluted to a 50/50 mix and sprayed on or around the plants as fertilizer.

Worm composting systems that capture the dark brown liquid that drains from the bottom of the bins should be applied back into the bin when extra moisture is needed. This dark brown liquid may be toxic to plants because of the organic acids that are produced.

The nutrients present in the compost depend on the type of waste that was fed to the worms. If the pH needs to be raised, limestone or calcium carbonate may be added.

Soil – Vermicompost improves soil aeration, enriches the soil with micro-organisms such as phosphate and cellulose as well as aiding the soil in water retention. Worm castings have 10 to 20 times higher the microbial activity than in the soil that the worms ingest. Vermicompost will attract other earthworms that are already in the soil to become more active.

Plant growth – Germination will be enhanced as well as plant growth and an increase in crop yield by improving the root growth. Vermicompost adds micro-organisms to enrich the soil.

Economic – Vermicomposting reduces the amount of waste going into landfills.

Environmental – The act of making vermicompost reduces the amount of greenhouse gases being emitted into the air as compared to landfills and incinerators.

Commercial Vermicomposting

Large scale operations of Vermicomposting are practiced in Canada, Italy, Japan, Malaysia, the Philippines, and the United States. Some of the commercial operations produce worms to sell to the home Vermicomposting market. Two systems are used for the large scale vermiculture, one is the windrow system and the other is the raised bed or flow through system. Windrow consists of large bins, usually with concrete bottoms to prevent predators from accessing the worms.

Organic material that has bedding material is added to the bin for the worms to live in while adding plant matter will feed them. These large scale systems will use large quantities of the following:

* Dairy cow or pig manure

* Sewage sludge. Cornell Waste Management has shown that land that had sewer sludge (bio-solids) applied was devoid of worms.

* Agricultural waste

* Food processing and grocery waste

* Cafeteria waste

* Grass clippings and wood chips

Raised bed or flow-through system is used with the red wigglers and is the preferred method for Vermiculture in colder climates. The red worms moves upwards to the new food source which makes the separation of worm from worm castings easier. The castings are harvested by using a breaker bar to pull across the large mesh screen on the bottom of the bed. These castings are then packaged and sold to consumers.

Home Vermicomposting

Vermicomposting can be accomplished on a smaller scale for the homeowner who wishes to reduce the amount of kitchen waste (free of meat and dairy products) that goes to the landfill into usable fertilizer. The preferred containers are made from plastic, wood, or Styrofoam. Metal containers will conduct too much heat, are susceptible to rusting, and harmful heavy metals may be released into the compost; therefore, not recommended for use. Wood containers made from Western Red Cedar are said to have “longevity” in composting. Some woods may contain resinous oils that can harm the worms, however.

List of kitchen waste matter than can be used in the feeding of the worms include:

* All fruits and vegetables (including citrus and other “high acid” foods)

* Vegetable and fruit peels and ends

* Coffee grounds and filters

* Tea bags (even those with high tannin levels)

* Grains such as bread, cracker and cereal (including moldy and stale)

* Eggshells (rinsed off)

* Leaves and grass clippings (not sprayed with pesticides)

Worm bins need aeration as well as drainage; therefore the bin should have holes in the bottom for the excess liquid to drain out. Wooden bins will need to be replaced eventually due to rotting over time.

Climate and temperature

The redworm will feed at temperatures between 59-77 degrees Fahrenheit. The bins will need to be placed in an area that does not drop below 50 degrees Fahrenheit and not over 86 degrees as this will harm them. Adding too much waste can heat up the worm bins during the decaying process and will kill the worms.


Harvesting worm castings is easier the smaller the operation. The worms will have to be sorted from the vermicompost once the bin has built up an abundance of compost. Sorting can be done by hand by dumping the bin and sorting by hand. Another method is to let the worms do the work for you by dividing them into smaller containers and letting them come to the top of the vermicompost to be taken off and put into another bin to start the process over again. It is time to harvest when the bin has accumulated an abundance of vermicompost and there are no food scraps or bedding left to be decomposed.

Worms produce a small, oval shaped yellowish egg/cocoon in which these should be returned to the bin to allow for worm reproduction.

Vermicompost is richer in nutrients than other compost made by different methods, although adjustments will be needed for magnesium and pH balance. Vermicompost is also rich in microbial life which turns nutrients left in the soil into a plant soluble food. Worm castings will keep the nutrients from washing away by adhering to the worm mucus that is present in the vermicompost.

The two most common problems with new vermicomposters is the fear of the worms escaping and odors. When new worms are added to a bin, a few may try to escape but will quickly adapt and remain in the bin with the addition of food scraps. Placing the bin in a lit area will also keep the worms contained. A properly maintained worm composting system is odorless. In order to avoid bad smells, air holes should be added to the cover of the bin as well as stirring the contents occasionally.

The removal of some of the compost may be required if it becomes too deep or too wet; an unbalanced bin will have the smell of ammonia and will need to be amended. If the compost is too wet, add dry, shredded newspapers or dry bedding and reduce the amount of food scrapes that are high in moisture. Fruit and vinegar flies are common during warm weather. To avoid these pests, keep the top of the compost covered in a layer of bedding material.

Image Caption: Healthy population of Reds in a disturbed worm bin. Credit: Red58Bill/Wikipedia (CC BY 3.0)