Vermicomposting, or composting with worms, is a fantastic way to quickly turn your kitchen scraps into a nutrient-rich soil amendment. It's cheap and easy, and when managed properly, can even be done inside your house.
Red wigglers, Eisenia foetida, are the best worms for vermicomposting. They are relatively hardy, reproduce quickly, and consume their own weight in organic matter each day. Unlike the common earth worm, red wigglers live near the surface of the soil, so can be fed and managed quite easily inside a bin.
There are a variety of options for your worm bin, but you'll at least need something eight to twelve inches deep with a lid. This could be a five gallon plastic bucket, a Rubbermaid container, or a wooden crate. Whatever you use, make sure you keep the lid closed but not shut tight, as this restricts air flow. Red wigglers like the dark, but they also like oxygen. Plastic containers are better for inside the house, but require a few drainage holes at the bottom to avoid high humidity and over saturation. Place a tray or extra lid underneath to catch the liquid that drips out - worm compost tea is a great fertilizer! Untreated wood, while not as long-lasting, readily absorbs moisture and has adequate drainage. You can drill a few holes in the bottom to collect the compost tea, but make sure they're at least six inches apart. Prop the corners up on blocks, find a tarp or tray to collect the drippings, and you're all set!
When starting your worm bin, you'll need six to nine inches of fluffed bedding. Shredded newspaper mixed equally with peat moss or potting soil works great. Moisten little by little, allowing the bedding to soak up water to the point where it feels like a damp sponge. Then add your worms! A small container like a five gallon bucket only needs a handful, while a large crate could use a whole pound. We got our worms from the Wonder Worman, but you can usually find red wrigglers at a bait shop as well. Keep your bin in a warm, dark location that stays between 40-80 degrees Fahrenheit - in the garage, under the sink, or in a shady area of the yard - and don't feed for a week. The worms will survive off their bedding. Then start small with a sprinkling of leafy greens, gradually building to a half a pound of food scraps per day for each one pound of worms.
Feed your wigglers fruits, vegetables, coffee grounds and filters, tea bags, crushed egg shells, and shredded junk mail at any time; and bread, pasta, onions, and garlic sparingly. You may also want to add some sort of grit (sand, sterile soil, oyster flour) to your bin to help worms chew through the tougher food. Stay away from citrus, dairy products, meat, fresh manure, and oily or processed food. These will attract rodents and make your worm bin smell. Not adding these foods and your bin still smells? Check the moisture level and drainage. You may need to add some dry newspaper or drill more bottom holes. Or you may be feeding your worms faster than they can break it down, resulting in spoiled produce. Bury the food that's already there and cut down on amount or frequency of feedings. As your worms reproduce, they'll be able to take on more scraps.
After three to four months, you'll most likely have some worm castings - aka worm poop - to harvest. One way to do this is to shove the castings to one side and fill the other with fresh bedding and kitchen scraps. In a week, most of the worms will have migrated over to the food, and you can harvest the castings all at once, picking out remaining worms and cocoons as you go. You can also just expose the inside of the container to sunlight and let the worms burrow down, harvesting layer by layer until you reach the bottom. Put worms and cocoons aside and place in fresh bedding once you're finished. Use the worm castings as a soil amendment, mixing some in around the base of each plant. It is rich in both macro and micro nutrients, as well as beneficial micro-organisms, making it the perfect organic compost for your garden or house plants! It's so easy, and a great project for kids!
Lisa Sanco, WGC Horticulturist & Program Manager
Grant Tandy, Hopservatory Manager, NASA JPL Solar System Ambassador