How Vermicomposting Works

Worm Compost Food and Established Bins

Worms love to munch through your leftover organic waste. Just remember to watch out for the foods that can harm them.
Lisa Fletcher/iStockphoto

Now comes the fun part of having a worm bin -- feeding the little guys. You can bury just about anything that originally came out of the ground in the bin. Coffee grounds and filters, tea leaves and bags, fruit and veggie peels and cores, paper, rice, grits, and natural fabrics are all things that can go in the bin. Eggshells that have been washed out and ground up are also an excellent source of calcium for the worms.

The following items make good worm food:


  • Leafy greens
  • Potatoes
  • Non-acidic fruits and vegetables (tomatoes, green peppers)
  • Low-acidity citrus
  • Coffee & tea grounds
  • Rice
  • Grits
  • Paper
  • Cotton
  • Eggshells

There are also several items that will harm the worms. For one, don't feed them anything fatty or oily. Worms can't digest meat proteins or lactose, so no dairy products either, like milk or cheese. While worms do like egg shells, the egg cannot go in the bin. Citrus and salt can actually harm the skin of the worms. We mentioned earlier that worms breathe through their skin, so just imagine if your lungs were on the outside of your body and someone decided to rub salt and lemon on them -- you probably wouldn't appreciate it either.

These items will harm your worms. Never give them:

  • Butter
  • Oil
  • Salad containing salad dressing
  • Eggs
  • Meat
  • Highly acidic fruits and vegetables (lemons, limes, oranges)
  • Hot peppers
  • Salt
  • Animal waste
  • Plastic
  • Synthetic materials
  • Insecticides

Once you've had your worms for a while, you'll get a feel for what they like to eat and what they don't. You'll also know how much to feed them and when. If your bin starts to smell bad, you're either feeding them so much that they can't keep up, or you're not burying the food well enough under the bedding.

Established bins that are healthy begin to reproduce worms and attract other decomposers. If you see other insects crawling around in there, don't be worried. It's OK unless there are a lot of flies hanging around. If you have a lid on your worm bin and bury your food well, you should not have to worry about flies or maggots. These other insects are helping the process, making sure that you can compost even more of your organic waste. After a while, you may also see tiny white sacks that may appear to be maggots. These are actually worm egg sacks -- or possibly even baby worms.

Your worm population should double in size every three months or so. When this happens, you can build new worm bins and transfer some worms over if they get to be too much for one area. If you feel that you can't keep up with the feeding schedule, you have a few different options. Teach your neighbors how to compost and donate some worms to them, set your worms free -- although this is a waste of really good worms -- or go fishing. They make great bait.

We've saved the best for last. Did you know that your worms can provide you with black gold? Read the next page to find out just how valuable it can be.