Starting a worm compost is gross, easy, and great for the Earth

[Illustration by Lorenza Centi for Mic]
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Humans tend to waste a lot of food. It's a problem that has led innovators to come up with all kinds of ideas — for how we could change grocery shopping to how we could change cooking to how we could change restaurants. The issue is that food waste takes over landfills, piling up faster than it can decompose and releasing harmful gases when it does. But while we still wait for the solution to humans' destructive tendencies, the other side of the solution is finding a better way to deal with our food waste. Enter: Worm composting.

Food left to decompose in a landfill releases methane, a greenhouse gas that is 28 times more potent than carbon dioxide and becomes acidic enough to release potentially harmful chemicals from plastics, metals, and other trash that is 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.

Of course, 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, and can be done 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.

The difference between composting and vermicomposting

Lots of people confuse composting and vermicomposting as being one and the same, but they're quite different.

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

By contrast, vermicomposting makes use of earthworms to do the decomposing, along with mesophilic microbes that function at moderate temperatures, usually between 68 to 104 degrees Fahrenheit. This has earned worm composting the nickname "cold composting." The lower temperature requirement also makes worm composting a bit more versatile: "Because odors and hot vapors are not a byproduct of vermicomposting like they are with composting, it can be done indoors," Churchill says.

[Illustration by Lorenza Centi for Mic]

This difference is quite important to keep in mind because many people make the mistake of thinking that hot composting is worm-compatible. Sometimes, people will make the mistake of adding worms to a hot compost bin. It's a bit of a gruesome oversight.

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

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 will cost somewhere between $10 to $30 depending on the quality. The worms themselves will cost, at minimum, $35, according to Sherman.

You can cut down significantly on the up-front investment with a little do-it-yourself ingenuity, though. Here's how.

  • 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.

Once you've scored your bin, you'll need to take 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.

  • 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.

Adding the worms

No matter if you go the DIY route or decide to shell out some extra money for your bin and bedding, you're going to have to buy some worms. There are lots of different types of earthworms, but there are only a handful that are ideal for vermicomposting. Those are epigeic earthworms. "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.

Sherman recommends getting 1 pound of worms, which will give you about 1,000 worms to start your bin.

Once you have the bin ready and filled with bedding, take your worms and gently empty them 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 will start to head under the bedding to get away from it. Give them a day or two to get adjusted.

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 that the worms are going to swarm to the food. "They picture dogs; you shake the food and they come running. Worms are more chill," she says. For this reason, it's important to make sure you don't overfeed them. "Give them a small amount of food, let them consume it, and then give them some more," Sherman says.

[Illustration by Lorenza Centi for Mic]

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

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.

  • Light separation

On a sunny day, or under bright indoor lights, lay down a tarp and dump out your worm bin so what was on the bottom is now on top. What you'll see is vermicompost, which looks and smells like soil.

While you're harvesting that, the worms will move away from the light and head toward the bottom of the pile. Reset your bin with bedding and put the worms back in. Sherman says the whole process usually takes her an hour to 90 minutes to do by herself.

  • Sideways harvesting

If you'd rather not interact with the worms, sideways harvesting the best option.

To do this, start feeding the worms only on one side of the bin. This attracts the worms to that side. Over the course of a couple of weeks, the worms will fully migrate over to that side of the bin. This will allow you to harvest the side that they have abandoned.

Once you've collected the vermicompost, add bedding to the harvested side and allow the worms to return. They'll slowly make their way back and you can run the same process, drawing the worms to the fresher side so you can harvest again.

  • Vertical harvesting

To do vertical harvesting, create a second bin identical to your first and fill it with bedding. Fill your original bin to the brim with bedding. and set your second bin on top of it. Start putting food waste in the top bin. Over time, the worms will make their way through the holes and into the top bin. This will leave just the vermicompost in the lower bin for you to harvest.

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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