Worm composting turns kitchen scraps into the best fertilizer on earth. Worm castings contain more nutrients than regular compost. They improve soil structure. They help plants resist disease. And you can do it indoors in a small bin.
I started a worm bin under my kitchen sink three years ago. My houseplants have never looked better. Here is everything you need to know about vermicomposting.
What Is Worm Composting (Vermicomposting)?
Worm composting uses special composting worms to break down organic waste. The worms eat your kitchen scraps. They produce castings (worm poop) that is supercharged plant food. The process is clean, odorless, and faster than outdoor composting.
Regular earthworms from your garden will not work. You need red wigglers (Eisenia fetida). Red wigglers eat half their body weight in food scraps every day. They reproduce fast. And they thrive in the confined space of a worm bin.
Find red wiggler composting worms on Amazon.
How to Set Up a Worm Bin
Step 1: Get a bin. A plastic storage tote works great. 10 to 15 gallons is a good size. Drill 10 to 12 small holes in the lid for air. Drill a few holes in the bottom for drainage. Place a tray underneath to catch any liquid.
Step 2: Add bedding. Shredded newspaper, cardboard, or coconut coir. Soak the bedding in water. Wring it out until it feels like a damp sponge. Fill the bin about three-quarters full with bedding.
Step 3: Add worms. Start with one pound of red wigglers. That is about 1,000 worms. Spread them on top of the bedding. They will burrow down on their own.
Step 4: Feed them. Bury a small amount of food scraps under the bedding. Start with half a cup per day. Increase as the worms multiply. Cover the food with bedding to prevent flies and odor.
Step 5: Keep them comfortable. Worms like temperatures between 55 and 77 degrees. Keep the bin indoors in a closet, under the sink, or in the basement. The bin should have no smell at all. If it smells, something is wrong.
What to Feed Your Worms
Good worm food: Fruit and vegetable scraps. Coffee grounds and filters. Tea bags. Crushed eggshells. Bread and pasta (small amounts).
Bad worm food: Meat, dairy, oily foods. Citrus and onions (too acidic). Spicy foods. Processed foods with preservatives.
Chop food into small pieces. The smaller the pieces, the faster the worms process them. Bury food under the bedding. Never leave food on the surface. Surface food attracts fruit flies.
How to Harvest Worm Castings
After three to six months, the bedding will be mostly worm castings. It is time to harvest. Here are two methods.
Method 1: Light method. Dump the bin contents onto a tarp under a bright light. Worms hate light. They burrow down. Scrape off the top layer of castings. Wait a few minutes. Scrape again. Repeat until only worms remain. Put the worms in fresh bedding.
Method 2: Migration method. Push all the bin contents to one side. Add fresh bedding and food to the empty side. Over a few weeks, the worms will migrate to the fresh side. Harvest the castings from the old side.
Using Worm Castings
Worm castings are powerful. Use them sparingly.
Potting mix: Mix 10 to 20% worm castings into potting soil.
Top-dressing: Sprinkle a thin layer around plants. A tablespoon per small pot. A quarter cup per large plant.
Compost tea: Steep one cup of castings in a gallon of water for 24 hours. Use the liquid to water plants.
A little goes a long way. Worm castings are five to ten times more concentrated than regular compost.
Frequently Asked Questions
Do worm bins smell?
A healthy worm bin has no smell. If it stinks, you are overfeeding or the bin is too wet. Add dry bedding. Stop feeding for a week. The smell should disappear. A properly managed worm bin smells like fresh forest soil.
How many worms do I need to start?
Start with one pound of red wigglers. That is about 1,000 worms. They will double in population every three to six months. One pound of worms can process about half a pound of food scraps per day.
Can I use regular earthworms for composting?
No. Regular earthworms (nightcrawlers) need deep soil and cool temperatures. They die in worm bins. Red wigglers (Eisenia fetida) are the only worms suitable for bin composting.
What is the liquid that drains from the worm bin?
That liquid is leachate, not worm tea. It is the water that drains through the bin. It may contain harmful bacteria. Do not use it directly on edible plants. Dilute it heavily or pour it on ornamental plants only.
