How to Compost with Worms (Vermicomposting)

Now that the summer is over and the winter season is approaching, Green Guerrilla would like to share how you can start composting over the winter months indoors… and with worms! So, let’s get started…

What is vermicomposting?

  • “Vermi” is the latin worm for worm
  • Vermicomposting is the process of composting food scraps using worms
  • Red wiggler worms are most commonly used
  • They can eat and expel close to their own weight every day
  • They work in partnership with fungi and microbes such as bacteria that help the breakdown process

Reg Wiggler Worms

What is vermicompost?

  • Vermicompost is mostly worm castings or worm “poop”
  • If done correctly it will not smell bad… it should have a faint earthy smell
  • It is ready for harvest when it is dark, crumbly and moist
  • A new bin can make compost in as little as three months!


Worm castings or "poop"

Worm castings or “poop”


How to Build & Operate a Basic Worm Bin

1. The Worm Bin

  • Choose a shallow bin: 20 to 30 cm (8 – 12”)
  • It can be a wooden boxes, galvanized metal wash tub or a plastic utility tub
    • Drill several 5 mm (¼”) holes in the lid for air circulation

The Basic Worm Bin

 2. The Bedding

  • Bedding provides the worms with a balanced diet, as well as a damp, aerated home. Bedding should be light and fluffy to allow for air flow
  • Common bedding materials include a combination of of the following:
    • Shredded newspaper or corrugated cardboard, garden soil, coarse sawdust, peat moss, dry leaves
    • My favorite combination is equal parts dry leaves (or shredded paper), soil and peat moss
  • Add 1 cup of water at a time to the bedding until it is moist like a wrung-out sponge.
The Bedding

The Bedding

 3. The Food

  • Keep a container under your sink or on your counter for kitchen food scraps.
  • Recommended foods:
    • Vegetable and fruit peels, coffee grounds/filters, tea bags, egg shells (crushed and in small amounts), pizza crust, spaghetti, corn flakes, beans, etc.
  • Foods to be avoided:
    • Meat, fish, cheese, butter, oily foods (like peanut butter or salad dressing), animal products or citrus peels in large amounts.
The Food

The Food


Acceptable & Unacceptable

 4. Feeding the Worms

  • Once your kitchen container is full empty the contents into the worm bin (about once per week)
    • Dig a hole and bury your food waste in the bin
    • A nine-spot system works well. If you bury your foods scraps about once a week, you won’t have to dig into a region that has food for nine weeks. By then, most of the food in that spot is composted.
    • Cover the partially rotten food with at least 3 cm (1”) of bedding materials.

      The 9-spot system

      The 9-spot system

Worms migrating towards food scraps

Worms migrating towards food scraps






 5. Temperature

  • Ideal temperature is between 16 to 27°C (60-80°F).
  • If your worms are outdoors, be sure to bring them in if the temperature drops below 5°C (40°F).

 6. Harvesting Compost

  • Worms will have consumed most of the bedding in 3 to 6 months and the vermicompost (worm castings) will need to be harvested.
  • There are two ways to harvest castings:
    • Move the compost to one side of the bin and add fresh bedding to the other side. Then only bury food on the new side. In 6 weeks the worms will have moved to the new side and you can harvest the finished compost.
    • Or, you can put the contents of the bin onto a newspaper or plastic sheet under lights or bright sun. Make small piles and let them stand for 10 minutes. The worms hate the light and will migrate to the bottom of the pile. Remove the finished compost from the surface of the piles until you see the worms. Repeat until there are worms mixed with only a little compost. Return the worms to the bin with fresh bedding.


How to Build & Operate a TIERED Worm Bin

A tiered worm bin is not much different than a basic worm bin. The only difference is that you can stack several tiers or levels on top of the base. This means you can add more food scraps, separate your worms and compost easier and collect liquid or “leachate” at the bottom.

 1. The Worm Bin

  • Choose a base and tiers for the worm bin.
    • You will need one bin for the base and 3-5 bins for the tiers
    • Choose shallow bins for the base and tiers: 20 to 30 cm (8 – 12″)
    • The tiers should be able to stack on top of the base and fit inside one another.
  • The base
    • Do not drill any holes in the base.
  • The tiers
    • Drill a patterns of 6 mm (1/4 inch) holes across the entire base of each tier. The holes should be regularly spaced at approx. 50 mm (two inches) apart in all directions. This is the minimum number of holes… I always like to drill more.
    • The holes will allow for drainage and the upward migration of worms to the next tier.
    • Also drill a row of 6 mm holes 50 mm apart in a continuous line aroud the walls of each tier about 10 cm under the rim of the bin.
    • You do not need to drill holes in the lid.
  • Set your first tier inside the base bin and line with a layer of newspaper. Newspaper only needs to be placed in the first tier. When you add the second and third tiers, they should be placed directly on top of the bedding material of the tier underneath it.
  • The base bin will collect any liquid or “leachate” produced by your worm bin, which will help keep it from getting too wet.
The Base Bin

The Base Bin

A tier with worm holes

A tier with worm holes

The first tier with a layer of newspaper

The first tier with a layer of newspaper


2. The Bedding

  • Mix the bedding the same as in Step 2 above, but add it to the first tier (not the base).
The first tier with bedding

The first tier with bedding

The bedding material

The bedding material


3. The Food & Feeding the Worms

  • Collect food scraps and feed the worms that same way as in Steps 3 & 4 above.

4. Add a Stacking Bin

  • When your first tier is filled with food scraps, it is time to add a second tier.
  • Put the second tier on top of the first tier making sure the holes of the second tier are touching the bedding materials in the first tier.
  • Add enough new bedding materials to fill your bin 1/3 – 1/2 of the way
    • Mix equal parts soil, shredded leaves or paper, and coconut coir or peat moss
    • Add water and mix. It should feel moist like a wring out sponge
  • Continue to feed your worms as outlined above. When your worms have eaten all of the food in the first tier they will move up through the holes in the second tier.
A completed worm bin: The base bin, three tiers and the lid.

A completed worm bin: The base bin, three tiers and the lid.

5. Liquid Collection

  • Check the base bin every month for liquid or “leachate”
  • If the leachate smells bad, do not use it. It could contain microbes that are harmful to plants. Empty the liquid into a container and flush it.
  • If the leachate smells earthy, you can dilute it with 10 parts water to one part leachate (10:1) and water your non-edible plants.
Base bin with leachate collection & first tier

Base bin with leachate collection & first tier

6. Harvesting Compost

  • It will take 3-4 months (after a tier has been filled) for the worms to eat everything in a tier. And another couple of months for the worms to move into the next bin.
  • After approx. 6 months you will be able to harvest the compost in a tier.
  • Remove the finished tier and empty it into your garden, sprinkle it on the grass or add a layer of approx. 6 mm to houseplants.

Before & After


My lilac bush before & after adding a full tier of worm compost

My lilac bush before & after adding a full tier of worm compost


Composting with worms is pretty easy once you get going. If you have any questions, please feel free to contact Green Guerrilla. Thank you for reading!


Brie Bennett
Green Guerrilla Sustainability


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