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Urban Worm Company - Vermicomposting - The Ultimate Guide for the Beginner and Beyond⚓︎

What is Vermicomposting⚓︎

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Vermicomposting, or worm composting, is the decomposition and humification of organic waste via an ecosystem of microbes and earthworms.

How is Vermicomposting Different Than Composting⚓︎

Composting is a microbe-centric decomposition process. Decomposition begins with mesophilic microbes that thrive in temperate conditions. These microbes then give way to thermophilic microbes that can raise the temperature in compost piles to temperatures well over 150 degrees F.

Vermicomposting bins are fed in thin layers of no more than 1-2 inches which allows for any heat to escape.

As Red Wigglers need 55-90°F in means that vermicomposting is dependent upon surface area, limiting the amount of waste that can be processed in a given space unless creative solutions are found to stack bins atop one another.

Composting operations are difficult without 3 feet of depth to form a hot core to trap heat and invite thermophilic microbes.

Soil Benefits of Vermicompost⚓︎

  • Soil aggregation - The ability for soil particles to bind to one another and form the pore spaces necessary for retention and exchange of water and oxygen, helping in water retention.
  • Carbon-heavy organic matter - The humus in vermicompost is also needed in top soils.
  • Earthworm attraction - Soil rich in organic matter, like that from compost and vermicompost, attracts earthworms which further aerate the soil and enrich the soil with their worm castings.

Earthworm Basics⚓︎

Not all earthworms are good for vermicomposting. Only about 7 species out of the 7000-9000 known species are suitable for vermicomposting in captivity.

Earthworms are divided into 3 classes, depending on their burrowing capacity and the resultant depths at which they operate and consume organic matter:

  • Epigeic - Worms live and eat closest to the surface in loosely-packed environments like manure piles and the detritus on the forest floor. They do not burrow in soil. Vermicomposting worms are in the epigeic category.
  • Red wiggler (eisenia fetida)
  • European Nightcrawer (eisenia hortensis)
  • Indian or Malaysian Blue Worm (perionyx excavates)
  • African Nightcrawler (eudrilus eugeniae)
  • Endogeic - Worms live in the first few inches of the topsoil, create horizontal burrows, and tend to be of lighter color than epigeic worms.
  • Anecic - Worms are the deep burrowing earthworms we typically call nightcrawlers. They come to the surface to forage for organic matter, dragging it down into burrows with can extend 6 feet or more under the surface.

Earthworm Fun Facts⚓︎

  • There are 7000-9000 earthworms species in the world
  • Worms breathe through their skin
  • Worms are hermaphroditic, meaning they possess both male and female reproductive capabilities
  • Earthworms have 5 hearts

Worm Tea vs Leachate⚓︎

Leachate is excess moisture that has leached through your vermicompost. This promotes anaerobic conditions, which are not conducive to healthy vermicompost

Worm tea is a deliberately-produced liquid. Vermicompost is suspended in oxygenated water in order to support additional microbial life before being fed to plants. To keep the mixture of microbes feed additives like kelp meal are often added to the mix.

Choosing Your Worm Bedding⚓︎

Worm bedding is critical for maintaining moisture, a high carbon-to-nitrogen ratio, and an aerobic environment.

Worm bedding includes things like paper and cardboard waste, leaves, leaf mold, coconut coir, peat moss, aged horse manure, and a commercial product called Pitt Moss.

A carbon-to-nitrogen ratio of 50:1 or higher is required for vermicomposting, requiring lots of initial bedding and ongoing additions of it along the way. It’s likely unnecessary to know your carbon-to-nitrogen ratio, just understand that you should never be concerned with having too much bedding, relative to food waste. This is due to bedding also being a food source for the worms, just at a slower rate.

Selecting Your Feedstock and Knowing How Much to Feed Your Worms⚓︎

Careful with moisture levels, meats, and other fatty foods.

  • Summer melons like cantaloupe, honeydew, and watermelon
  • Fall fruits like pumpkins
  • Banana peels
  • Coffee grounds
  • Apple cores
  • Assorted fruit and vegetable waste

How Much Should You Feed Your Worms⚓︎

There is a lot of information stating worms can eat 50-100% of their own weight each day, and it is likely all incorrect.

A very experienced, well-known California-based vermicomposter estimates that his worms eat an estimated 25-33% of their own worm weight daily.

Things that can effect diet:

  • The ecosystem of microbes and worms in your worm bin will ultimately consume everything in your bin. This includes nitrogen-rich food and carbon-rich bedding.
  • Your carbon-rich bedding like paper and cardboard is also a food.
  • A new bin will process organic waste much more slowly than an established bin.

An initial place to start for a new bin is no more than 1/4 the initial worm weight in the first week. Re-assess one week later.

Should You Chop or Freeze Food Waste⚓︎

Chop up food waist as you can to increase the surface area available to microbes.

Freezing can help spread large quantities of food over a few days, and it can rupture cell walls.

Maintaining Conditions in Your Worm Bin⚓︎


Every worm species has its own preferences for temperature, but most do best in 70-80°F bins, with 55°F and 95°F being the extremes that they can tolerate.


Food waste typically has a high (80+%) water content, meaning your bin is likely too wet. You should be trying to keep your bin withing 68% to 75% moisture content.

Leachate is not a good sign, it means you have excess moisture. It can lead to anaerobic microbes, worms going deeper than they need to follow the water, and makes harvesting difficult.

  • Anaerobic Conditions - As excess moisture seeps down into the vermicompost, it displaces air in the pore spaces. The microbes in the vermicompost consume the available oxygen in these pore spaces that are now occupied by the leachate, eventually producing an anaerobic, oxygen-deficient environment. This is bad for both the worms, and the microorganisms which are helping to maintain a healthy bin.
  • Deeper Worms - In normal conditions worms will be near the top of the bin eating the fresher organic waste. However, worms are also attracted to water, and will often follow it to undesirable depths. In a continuous flow or multi layer bin system, worms moving to deeper depths means harvests can often be full of worms, reducing the healthy population.
  • Difficult Harvests - Even without wormy harvests, wet vermicompost is difficult to screen as it will tend to clump and form aggregates that are too large. When harvesting the processed vermicompost you want to keep it with a lower humidity so it does not spoil or clump.


While important, pH will be much easier to manage than temperature and moisture. Vermicompost should be pH neutral to slightly acidic, though slight deviations into the alkaline range may be ok.

If you are careful with what you feed, and have sufficient bedding, pH will likely not be a concern.

Using Your Castings⚓︎

Direct Application⚓︎

One cup of vermicompost, applied near the roots, is sufficient for most plants.

When mixing with a potting or grow media mix a substitution rate of 1 part compost to 10 parts mix.

Worm Tea⚓︎

Worm tea is a deliberately-produced liquid made from worm castings. It is produced by suspending fresh vermicompost in a bottle or bucket that is being oxygenated or agitated. A slow releasing energy source like alfalfa or kelp meal needs to be added to the mixture to keep the biome healthy. Once mixed it needs to set, being aerated, for 24-28 hours and then quickly applied to plants as a root drench or low pressure spray.