Worm composting, or vermicomposting, is an important part of a sustainable home. Composting reduces the amount of organic waste that makes it to a landfill, which often doesn’t decompose*, and turns your fruit and vegetable scraps into a nutrient-rich fertilizer by passing through the digestive tract of worms and other beneficial microorganisms. Their excretion, called worm castings, or vermicast, is nitrogen-rich and full of moisture, and can be used as a fertilizer for your house plants, and your garden. Worms can take your coffee grinds, lettuce scraps, and apple cores, and turn them into fertile castings, which you can then in turn feed your little plants with.
The most common worm species for worm composting is the Red Wiggler (Eisenia fetida), though European nightcrawlers (Eisenia hortensis) may also be used. Red Wigglers are the most common variety because they are surface dwellers that live in rich organic soil, feed on decomposing plant matter, and eat up to half their size in food per day.
Your worm buddies can be used indoor or outdoor, but if you live in a climate with wild temperature swings, you might be better off with an indoor bin, since colder temperatures (below 10C) can kill your worms. I know a few people here in town who keep and maintain a worm bin year-round, but then move a few handfuls of worms into their outdoor compost bin in the summer, fully knowing that those worms will die come autumn frosts. The ideal temperature for your worms is between 15-25C, with temperatures below 10C and above 30C liable to kill them off.
*most landfills, due to their depth, create anaerobic environments, meaning that at depth, there is a lack of oxygen. Without that oxygen, or aeration, organic waste will not decompose, and can sit there for decades.
How to Build a Worm Bin
The easiest way to build a worm bin is to use a bucket, or a Rubbermaid bin between one to two feet in depth. Shallower than a foot, and you won’t have very much room for your worms to grow. More than two feet or so in depth, and your worms won’t be very effective at decomposing the organic matter at the bottom of the bucket. Some people prefer to use wooden boxes, because they are porous and will naturally breathe better and absorb extra moisture (which can kill your worm buddies), but they will decompose over time. If you do choose to use wooden boxes, make sure the wood isn’t chemically treated, which could kill your worms. Worm bins are also available commercially, for example, this bin sold here at vermiculture.ca.
1. Your bin needs to be highly ventilated. Drill a bunch of ventilation holes 1/8″ (3mm) along the sides of the bucket and in the lid. If you have a second bucket to sit the compost bin in, you can also drill 1/4″ (6mm) aeration holes in the bottom, and catch the ‘fertilizer juice’ in the bottom bin. If you are using a second bin, drill holes in the sides to aerate the ‘juices’. If you are sitting your bin outside, you definitely need the lid to prevent excess water from entering the system, but if the bin is inside only, you just need something to cover the top of the compost to keep pets out, and prevent flies from forming.
2. Now that your bin is full of holes, we have to make it habitable for your wormy buddies. Lay down a layer of ‘bedding’. Bedding is meant to replicate the natural habitat of the worms, and gives them a place to live and hide. It also assists in keeping the food scraps aerated and oxygen rich, and to absorb extra moisture. Too much moisture can kill your wormies by creating an anaerobic environment (the bad part about organic waste in landfills!)
Suitable bedding materials include:
- shredded newspaper
- shredded cardboard
- chopped up straw and dead plants
- peat moss
- sawdust from untreated wood
The bedding should be wet, but not sopping. Think “damp sponge”. Fluff it up a bit. Whichever bedding you choose will eventually breakdown and become part of the organic matter in the castings.
3. Throw a few handfuls of soil in to give your worms some ‘grit’ to help them digest the food waste and to introduce beneficial microbes into the environment. This step isn’t necessary, but it will speed up the growth of your worm bin.
4. Feed your worms. Start slowly, and as your bin grows, you can increase your food waste input. Bury it in a different place each time. Remember, red wigglers eat half their body size in food. So if you produce 1lb of waste each week, you need to have 2lbs of worms to fully compost it all. If you can purée or chop your scraps finely before putting them in the bin, they will break down faster.
Do’s and Don’ts of worm feeding:
- fruit and veggie scraps
- grains, cornmeal, and breads
- coffee grounds, filters, and tea bags (take the staples out of the tea bag!)
- dried, crushed eggshells (for pH balance in the soil)
- small amounts of citrus fruit (for pH balance in the soil)
- foods with oil, salt, or vinegar
- garlic, onions, chives, or shallots
- pet food, meat, fish, or dairy (these putrefy before they decompose)
- hard root veggies such as potatoes (hard for the worms to digest)
- high amounts of citrus fruit
*Greens (nitrogen rich): veggies and fruits, coffee grounds, tea bags, green grass clippings (without insecticides on them!), green garden waste, flowers
*Browns (carbon rich): dried leaves and brown grass clippings, pine and spruce needles, paper, cardboard, and newspaper, house plants, prunings and cuttings, sawdust (untreated wood), straw
*Other: (add minerals): egg shells (add calcium carbonate), wood and wood pellet ash (use sparingly for pH balance)
5. Finally, put another layer of dry bedding on top. This prevents fruit flies from forming. Put the lid on, or a well-fitted piece of cardboard, or even a piece of plywood, if it is left slightly askew for ventilation.
As your worm bin grows, don’t forget to maintain moisture, and stir everything up every few weeks to aerate the soil and assist with decomposition!
If you’ve taken care of your worm bin, within 3-6 months, your bin will be ready for harvesting (aka, your apple cores will have been turned into soil. By magic.)
Open your bin, and move any bedding and uncomposted vegetative material out of the way. Using gloves (or your bare hands, if you aren’t squeamish), scoop up sections of the moist worm castings and worms, and spread it out onto newspaper laid out on the floor in a ‘pyramid’ shape. Worms dislike light or sunlight, so once you’ve gathered all your finished worm castings into the pile, shine a bright light, or leave out in the sunlight for 5 minutes. The worms will wriggle their way down into the bottom of the pile.
Scoop the castings up and remove them from the pile. Wait another 5 minutes for the worms to hide again, and repeat until you have no more castings left, and then return the worms to the bin.
Go fertilize your plants!
Wormy Issues and How to Fix Them
Instead of rewriting all the problems you can or could have with your worms, you should check out this very informative article here @ urbancomposting.org *
*really, you should check out their entire website. It’s far more informative than this one post could possibly hope to obtain.
Indoor Composting in Yellowknife, a pamphlet produced by the City of Yellowknife
A Little Piece of Earth: How to Grow your Own Food in Small Spaces, by Maria Finn
Image from: http://queenbeecoupons.com/create-a-diy-worm-compost-bin/