Compost Indoors with Worms

Perfect for apartment dwellers, worm composting uses red "wigglers" to recycle food scraps and other organic material into a valuable soil amendment called vermicompost. Worms eat food scraps and become compost once they pass through the worm’s body. Vermicompost is great to use to grow plants!

For step-by-step instructions on how to get started, view this presentation and handout.

Why should I use red "wigglers"?

Red worms or "wigglers (eisenia fetida):

  • Eat fast
  • Tolerate disruption to their burrows
  • Tolerate a wide temperature range from 40-80 degrees
  • Tolerate acidity & moisture – but both must be kept in check
  • Reproduce fast
    • Baby worms are sexually mature in 8-10 weeks
    • 1 breeder can produce about 100 worms in 6 months
    • Worms hatch in 3 weeks – 2-3 worms per egg!

How do I prepare my bin and bedding for my worms?

  • Find a convenient place to store your bin between 40-80 degrees.  Some good places:
    • In the kitchen pantry or under the sink is most accessible
    • In the closet
    • On the balcony (but not in winter and not in direct sun)
    • In the basement or garage (but not if it freezes)
  • Prepare your bin
    • Select an opaque bin with a tight lid (worms are sensitive to light). Plastic bins are well contained, easy to maintain and transport.
    • The container should be 12" deep at most and opaque or covered with a dark cloth, since worms hate light.
    • Drill air holes in the lid and halfway down the sides.
  • Prepare your bedding
    • Tear newspaper into strips, about 1/2" wide.  No glossy or colored pages.  Black ink is carbon based and harmless to worms.
    • Dampen with water with a spritz bottle. It should be as damp as a wrung-out sponge, not dripping wet.
    • Fill bin 3/4 full of damp bedding

Where can I get red worms to start composting?

*Vendors have different types of bins, worm kits and classroom curricula.

In nature, redworms can be found in decaying leaves, manure piles or other organic material, such as compost piles. If you have access to such areas, you can collect your own redworms. A few handfuls are enough to start a bin, but add only small amounts of food scraps until the worm population increases enough to handle more (3-4 months).

What can I feed my worms and how?

Red Worms are Vegetarian!  They can eat:

  • Veggie & Fruit Scraps
  • Bread & Grains
  • Tea Bags, Coffee Grounds & Filters
  • NO meat or dairy
  • NO oily or cooked foods (steamed veggies are OK)
  • LIMIT citrus as it is too acidic and can lead to fruit flies

How to Feed Worms

  • Feed worms every 1-5 weeks
  • Check last feeding location to avoid overfeeding
  • Move bedding to create a hole or trench in a new location
  • Place food in opening
  • Cover up food with bedding, never leave it be exposed
  • Add more bedding if necessary

How can I ensure that my bin does not become too wet?

Since food is at least 50% water, you will generate “compost tea”.  This tea is full of nutrients and great to dilute in a pitcher of water and nourish your houseplants. 

Worms breathe through their skin and there is nowhere for moisture to go in a plastic bin.  When you feed your worms, look for condensation on the underside of the lid.  That is a key sign that it is too wet in your bin and the worms will be crawling the walls of your bin.  Picture the sidewalk on a rainy day, the worms come out of the ground because it is too wet down below!

Lots of moisture?
Push castings over to one side, tip bin up on a sneaker, let the moisture drain to the opposite corner, and use a dedicated turkey baster to draw out the compost tea.

Minimal moisture?
Add dry bedding.  When you close the lid, the dripping lid will "rain" down and be absorbed by the dry bedding.  Or, leave the cover off for awhile to let excess moisture evaporate.

How can I avoid / manage odors and fruit flies?

Remember that with any composting project, if you manage it properly you can avoid problems in the first place. 

Odors will occur if:

  • Too much food in bin.  Slow down on your feeding, especially if you are waiting for starter worms to reproduce. 
  • Too wet, not enough air.  When the contents of your bin are too wet, the material gets heavy and anaerobic conditions create odors.  Turn and pluff your pile. 
  • The wrong foods are added. 
    • Too acidic if lots of citrus.
    • Stinky foods like rotten broccoli.
    • Never add meat, dairy or oily foods. 

How and when do I harvest the worm castings, or "black gold"?

Since about 50% of food is water, the volume of material will shrink, so do not worry about having that much soil.  You can  keep it on hand for when you need it. 

After about three months, the contents of your worm bin will begin to look like soil.  At that point you can either add more bedding and continue to build the pile up as long as there is more room in your bin.   Otherwise...

Let the Worms Do the Sorting

  • Push the finished castings to one side. 
  • Put fresh bedding in the empty side and bury only food in that side. 
  • Within about 4 weeks, your worms will move over in search of food and a cleaner environment. 
  • Then, you can harvest the finished castings. 
  • You may have to pull a few worms out, but most will have moved over. 
Dump and Hand Sort

  • This method will take several hours and is great if you want to get kids involved. 
  • Place a plastic sheet on the floor of a brightly lit room, or outside.   
  • Dump out the contents of your bin on the plastic. 
  • Separate the castings into several cone-shaped piles. 
  • Since worms are sensitive to light, as you remove the top and sides of the piles, the worms will burrow down.
  • Eventually, you will have a bunch of worms at the bottom of the pile.
  • Add the worms back into the bin with fresh bedding and food.
Adding Vermicompost or "Black Gold" to Houseplants or the Garden
  • Casting are usually very moist, so mix in equal parts of organic potting soil. Use to:
    • Top dress houseplants
    • Plant cuttings
    • Prepare new plants and give as gifts

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