An absolute beginner’s guide to worm composting

Slightly gross, but great for the planet.

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Humans waste a lot of food.

That food waste piles up in landfills faster than it can decompose, releasing methane, a greenhouse gas that’s 28 times more potent than carbon dioxide and becomes acidic enough to release potentially harmful chemicals from plastics, metals, and other trash that’s piling up alongside it.

If we just disposed of food waste in a more effective manner, it could instead be a good thing, which is the entire principle behind composting. Composted food waste has the potential to be utilized as fertilizer while also not contributing to landfill overflow.

Enter: Worm composting.

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Composting typically requires outdoor space to allow your food waste to decompose — something that not everyone has. That's where vermicomposting, or worm composting, comes in. Vermicomposting can be done indoors or outdoors, in a relatively small bin that can fit in a modest home or apartment. You'll just need some earthworm roommates who will take care of the waste for you.

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What’s the difference between composting and vermicomposting?

Composting vs Vermicomposting

"Composting is typically a hot process employing thermophilicor heat-loving microbes," explains Steve Churchill, the owner of Urban Worm Company. As the microbes decompose food waste, they can reach temperatures over 150° Fahrenheit, hot enough to kill off potentially harmful pathogens.

Vermicomposting, or “cold composting,” uses earthworms to do the decomposing, along with mesophilic microbes that function at moderate temperatures, usually between 68 to 104° Fahrenheit. The lower temperature requirement makes this process a bit more versatile: "Because odors and hot vapors are not a byproduct of vermicomposting ... it can be done indoors," Churchill says.

This difference is important; some people make the mistake of adding worms to a hot compost bin — a bit of a gruesome oversight.

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There's a rumor going around that if you add worms to a compost bin, then it will decompose more quickly. That's not true. You don't want to combine the two methods. The environment inside a compost bin is very different from a worm bin, and very different from what worms need to keep them alive.

Rhonda Sherman, the director of the Compost Learning Lab at North Carolina State University and author of The Worm Farmer's Handbook.

How to get started

At the most basic, you're going to need the following materials to start vermicomposting:

  • Worm bin
  • Bedding
  • Worms

If you choose to buy specialized material, expect to invest at least $150 in start-up costs. Worm bins designed for vermicomposting typically cost at least $100 and can push well beyond that, while worm bedding is somewhere between $10 to $30 depending on the quality. The worms themselves will cost, at minimum, $35, according to Sherman.

But, you don’t have to go that route.

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Making a bin

While there are fancy worm bins out there, you'll do just fine by going to the hardware store and grabbing a plastic container with a lid to serve as your DIY bin. Sherman recommends a 10 to 18 gallon container, which should cost less than $10.

Then, use a drill with the smallest available drill bit to create holes for ventilation. Sherman says you should drill holes no more than 1 inch below the top rim on the sides of the bin. Then, using a quarter-inch drill bit, she recommends creating about six holes on the bottom of the bin for drainage.

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Making bedding

For bedding, particularly in a small container, all you need is some paper and water. Sherman recommends using newspaper, but says shredded or ripped up office paper or cereal boxes will also work. Take your shredded paper or cardboard and soak it in water for about 10 minutes. And don't just dip it in — really let it sit in the water and soak it up. "If you just dipped it in, then it would the fibers would not absorb the water and hold it, and that's what you want," Sherman explains.

After 10 minutes, squeeze out the water, fluff out your makeshift bedding a bit, and add it to the bin. You'll want to fill your bin about halfway full with this paper bedding.

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Adding the worms

There are lots of different types of earthworms, but only epigeic earthworms are ideal for vermicomposting. "These worms don't live underground, they're not living in the soil, and they're not eating the soil. What they prefer is decomposing organic materials," Sherman explains. Churchill recommends either Red Wigglers or European Nightcrawlers.

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1 lb

The amount of worms Sherman recommends buying, which will give you about 1,000 worms to start your bin. Once the bin is ready, gently empty your worms out on top of the bedding. Then, Sherman says, just stand back and let them do their thing. Worms are sensitive to light, so they'll start to head under the bedding to get away from it. Give them a day or two to get adjusted.

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Adding food and waste

Once your worms are settled, you can start filling the bin with food waste and other organic material. Fruits and vegetables are almost always good — though try to limit the amount of citrus. Coffee grounds and filters, shredded napkins and paper towels, and similar materials can go in, too. Don't bother with animal waste like bones, meat, or dairy products.

Sherman notes that some people make the mistake of thinking the worms will swarm to the food — but it’s important to make sure you don’t overfeed them.

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[People] picture dogs; you shake the food and they come running. Worms are more chill. Give them a small amount of food, let them consume it, and then give them some more.

Rhonda Sherman

Above all, Sherman advises, there is one very important step for adding any food to your worm bin:

Make sure it’s covered.

Chop it up if you need to, and bury it under the bedding. If you don't, it will rot and attract flies, which nobody wants.

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Harvesting vermicompost

Vermicomposting is a slow process. Churchill says it'll be at least two to three months before you'll have to harvest the output: a rich, organic fertilizer that plants love. The material is sometimes called vermicompost or worm castings, though Sherman jokingly calls it "black gold."

All of these are very polite names for what it really is: worm poop. Once the time comes, there are three different approaches for what you can do with your black gold:

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Enjoy your worm poop

Once you've harvested the vermicompost, you can make use of it. House plants love it, and it can help ward off insects, pests, and disease. You can also sell it, as vermicompost is highly sought after. No matter what you decide to do with your fancy worm poop, you can rest assured that you've kept food waste from ending up in a landfill where it would simply contribute to climate change. That, all on its own, makes the process worth it.

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