Vermicomposting is a way to compost your food scraps with red worms, or Eisenia fetida. This is a great way to compost if your space is limited! A well managed worm bin can be set up in your house, apartment, or office. If your bin is well maintained, happy worms will make you vermicompost to add to your garden!
What You’ll Need
- Worm bin – purchase one or make your own! A 10-gallon bin is a great size to start with.
- Damp bedding – shredded newspaper or office paper. No color ink or glossy paper.
- 2-4 cups of potting soil
- 1/4 cup sand to help worms grind the food
- Food scraps – about 1 gallon. Do not add meat, dairy, citrus, or oily foods.
- Red worms – be sure they are Eisenia fetida. 1lb of worms works well for 1 gallon of food scraps per week.
- Whole sheets of newspaper – no color ink or glossy paper.
How to Vermicompost
- Clean the worm bin with soap and water.
- Set up the worm bin where temperatures will remain between 55 and 77ºF. They will survive temperatures a little beyond, but prefer this range.
- Add the bedding (enough so the bin is about 3/4 full), potting soil, and sand to the bin. Be sure this is as damp as a wrung out sponge. If it is too wet, add dry newspaper. If it is too dry, spray with a water bottle.
- Dig in the food scraps so they are completely covered by the bedding. Keep food covered so it doesn’t attract flies.
- Add the red worms.
- Add more bedding and potting soil if needed.
- Place whole sheets of damp newspaper on top of bedding to keep everything moist.
- Leave the lid off and on a light on for the first night so the worms know to stay in the bin. After the first night, put the lid on but keep it ajar for ventilation.
How to Maintain Your Worm Bin
Feed your worms one gallon of kitchen scraps per week. The food should provide enough moisture, but spray with water if it gets too dry. Add more bedding, potting soil, and sand as needed. Worms don’t need a lot of attention and can be left for up to 2 weeks if you are away.
Liquid will seep from the bottom of your bin because of the moisture inside. Drain the liquid from the bin periodically and discard. Do not use this on plants you will eat. It may contain toxins that have not been processed through the worm’s digestive tract.
How to Harvest Vermicompost
When the worm bin is full, you can harvest vermicompost. If you are using a multi-tray bin, add a new tray to the top and follow steps 3 & 4 listed above. The worms will move to the new tray and food, leaving vermicompost in the tray below.
If you are using a single tray bin, there are two ways to harvest vermicompost:
- Light Method – Remove the lid in a lit area and and the worms will move down in the bin to avoid the light. Scrape off the top layer of vermicompost until you see worms. Wait a few minutes for the worms to move down again, and then scrape off another layer. Continue this process until you’ve harvested as much as you can.
- Side-to-Side Method – Push everything in the tray to one side. Add new food and bedding to the side you cleared. Give the worms a week to move to the new food and leave the vermicompost behind. After one week you can harvest the vermicompost and continue adding food to your bin.
UW-Extension Master Gardener Manual: Foundations in Horticulture