Worm Composting Basics

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Worm composting has become a normal part of my weekly routine as I’ve sought to live more sustainably. Although I haven’t achieved the level of affection my granddaughter shows for the worms, she wants to name them, I am grateful for the work they do to cut down on my food waste.

Why Compost?

While we may think that food will decompose naturally in a landfill, that is not the case. Unlike a compost pile in your yard, food trapped in a landfill cannot decompose naturally and releases methane, a greenhouse gas that is at least 28 times more potent than carbon dioxide.

When we compost our food scraps we not only save our atmosphere from more methane, we create a soil enhancing fertilizer that improves the health and productivity of our gardens. Composting is a simple step we can all take to reduce our waste and improve our planets health.

Here is a quick video about my system.

Why Worm Composting?

  • Small spaces are no problem. Your worm bin can be whatever size makes sense for you.
  • Lack of outdoor space is not a problem. Worm bins can be kept indoors with no odor or mess. Many place their bin under a sink or tucked in a closet.
  • It costs nothing to set up. Most of us have a container lurking around our space that can be converted into a worm bin. It may not be cute, but it will be functional. Then all you need is bedding and food. Even if you don’t have a stack of cardboard boxes (hello Amazon deliveries) to dispose of, you likely have egg cartons, and if not friends and family will likely be willing to contribute to your cause.
  • Takes little time. I estimate I spend 10 minutes every two weeks on my worms.

What About The Worms?

Composting worms are generally not the same as the earthworms in your garden. Red Wigglers are the recommended worm as they are not fussy and do well in ‘bin’ conditions.

I got my worms from my neighbor who already had a bin going and was happy to get me started. If you know someone who already vermicompost you might be able to get a donation.

If not there are several places online you can order composting worms from. If I were ordering online I would buy Uncle Jim’s Worm Farm worms. 250 worms are about $30. I’d guess I started out with about that many worms, although you can order thousands from Uncle Jim’s website if you are starting BIG. The worms will reproduce in the bin and basically adjust their populations to the space available.

The BinWorm Composting

There are lots of different kinds of bins for worm composting available online and if you purchase one you won’t have to worry about requirements.

If you are looking to invest in a worm bin that looks more like a piece of furniture you can check out the handmade composters on etsy. This is the one I have my eye on.

However, if you are making your own there are a few things you’ll want to keep in mind.

  • Worms are photo-phobic, meaning they do not like light. Your bin needs to be made out of a dark material that will block light.
  • Every pound of worms needs about a square foot of space to be healthy. Make sure your bin size is large enough for your worm population. That said, nature is pretty intelligent and your worms will generally reproduce to fill the available space and then the population will stop growing and maintain the correct level from then on.
  • Your worms need air. Drill holes around the top of the worm farm and on the bottom of the container to allow sufficient ventilation. Set your bin on bricks or blocks of wood rather than on the ground so that the air can come in from the bottom.
    • The holes will also allow excess moisture to flow out of the bin. If you have the bin indoors set it in a tray of some kind that will catch any liquid.
    • If the holes on the bottom of your container are large enough that you are worried about the worms falling out (they don’t really, they tend to go up to where the food is) you can place a bit of screening across the bottom of the container.

Bedding for Worm Composting

Key to good bedding is remembering that your worms will actually eat the bedding, as well as the food you supply. If you think of the bedding as additional food for the worms you’ll understand why there are a few guidelines you’ll want to follow.

Bedding should be soaked and then the excess water squeezed out before adding to the bin. Worms need to stay in a moist environment to thrive. We want the bedding wet, but not sopping wet, more like a damp sponge.

Don’t pack the bedding down. Worms need air and places to crawl and move around, so the bedding should be loose and airy.

Bedding should be shredded. Cut up cardboard and shred paper. I soak my egg cartons just as they are and the worms don’t seem to mind, but egg cartons are not going to compact the way a clump of paper will. If you consider the worms desire to move around you’ll know what to do.

DON’T Use These Materials For Bedding

  • Paper or cardboard that is colorful. The inks can be toxic to worms.
  • Paper or cardboard that contains plastic like packing tape, labels, or the window in an envelope. Remove all plastic before adding it to your bin.
  • Paper receipts. Most receipts are thermal and are coated with BPA, a known carcinogen and hormone disrupter. Receipts can create problems for worms.

DO Use These Materials for Worm Compost Bedding

  • Plain brown cardboard like shipping boxes that you have cut up.
  • Shredded newspaper
  • Shredded mail that isn’t full of colorful ink or coated with plastic.
  • Coffee filters if you use unbleached paper filters.

What to Feed Your Compost Wormsworm composting basics

You’ll want to find a container to keep on your counter to collect your food scraps in. Making this process as easy and convenient as possible will be key to your success. World Market, Sur La Tab and other kitchen stores often have cute compost bins. I ordered this one from amazon and have been quite happy with it.  My suggestion is to look for one that has a space for a charcoal filter to insert in the top as this can help with odor. I’d also suggest looking for one with a liner, or interior pail that lifts out. The cute tin bin I used to have rusted out after a few year use and was harder to clean than the one I have now.

DON’T Feed Your Worms

  • Salty Foods
  • Spicy Foods, including hot peppers
  • Oil, or oily food. Asparagus in great for worms, asparagus drenched in olive oil, not so much.
  • Meat
  • Dairy Products
  • Processed foods with preservatives.
  • Citrus
  • Onions and garlic.
  • Yard clippings if there is ANY danger they have been treated with pesticides!
  • Soap
  • Tea bags. Tea is great for worms, but most tea bags contain plastic.

DO Feed Your Worms

  • Vegetable scraps like the tops of carrots, trimmings when making a salad, peels from vegetables etc. Generally these are all the scraps you have as your prepare a meal, before you coat them with oil etc.
  • Fruit scraps. Worms love fruit and aside from citrus they are all great for worm feed.
  • Pasta and grains like rice and quinoa. This would be the rice that has gone bad in the fridge, oatmeal if it was cooked in water ( not milk, no dairy) Pasta that has some tomato sauce is fine, but macaroni and cheese wouldn’t work.
  • Bread that has gone stale or molded.
  • Eggshells. Actually adding a couple of crushed eggshells every few weeks will keep your worms healthy. Their digestive system does well with some grit, which is why many people add a bit of soil to their beds.
  • Tea and Coffee. I’ve found too much coffee can be a problem, so I spread the grounds around my garden (or neighborhood) and the worms just get the coffee that is left in the paper filters. Tea should be either dumped from the tea bags or be loose tea.
  • Pesticide free leaves and grass clippings are great. I add leaves from my houseplants when I trim them. Unlike a traditional compost heap which needs lots of yard waste worms prefer food scraps, but a bit here and there is a fine addition.
  • Cut flowers that have wilted. (In limited amounts.)

Additional Tips and Trouble Shooting When Worm Composting

Worms are quite adaptable and can survive in temperatures ranging from 41 degrees to 86 degrees. Actually, our summers here in Southern California can get hotter than that and my worms have been fine in a shaded location. However, you should be aware of the weather and move your bins if you are expecting a hard freeze to somewhere protected. I’ve found in heat waves as long as I check that the bedding hasn’t dried out and the bin is in a shaded area the worms are fine.

Your worm composting bin shouldn’t attract any wildlife as there is basically no odor and a lid on the bin. I live in an area where I regularly see raccoons, squirrels, and stray cats. None of them have bothered my outdoor worm bins.

If you do notice any odor coming from your bins you are feeding too frequently and the worms cannot keep up with the incoming food. Stop feeding for a few weeks and everything should normalize.

Invaders do happen occasionally. We’ve had a bit of an ant problem where we live and at one point I had ants get into my bin. We cleaned up around the bin and I laid down diatomaceous earth on the ground. The diatomaceous earth (a powdered rock) cuts the outer skeletons of insects and kills them. I’d be cautious with chemical ant killers as any cross contamination can kill your worms. The diatomaceous earth won’t bother the worms, I’ve even sprinkled a small amount inside my bin, and I mean a small amount. Too much isn’t good for the worms.

This article from the Washington Post covers some other interesting aspects of food waste.

If you are curious about what sustainability is all about I suggest you check out this article, and if you want more information about going plastic free you can start here.

Would you consider worm composting?




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