How to Make the Ultimate DIY Worm Composter

How to Make the Ultimate DIY Worm Composter

How to Make the Ultimate DIY Indoor Worm Composter

Here’s the problem.

You’re looking to buy a worm composting bin on Amazon that's small enough to fit under your sink. There are a bunch of options, but they all have a massive, gaping flaw.

Literally. They have gaps!

Why build your own worm compost bin?

Now, I don’t know if you know this or not, but worm compost has way more than just worms in it. There's an entire ecosystem of microscopic little bugs living in there. It's such an interesting and diverse microscopic ecosystem that is led us to build the Micro Safari. Learn more about the Micro Safari Ecosystem Kit here, and keep reading below to learn how to build the best DIY worm composter. 

What You'll Need:

  • Waterproof, transparent storage container with gasketed seal & multiple closing clamps
  • Breathable, synthetic fabric
  • Sharp scissors (or flush cutters)
  • Packing tape
  • Cardboard scraps
  • Optional: Vaseline
  • Your first worms 
  • Organic material

What to look for in a compost bin

Back to the topic at hand, all these composters have gaps where the little bugs can crawl out and roam around your house. I don’t know about you but I don't want a bunch of bugs running around my home. Now look, these little critters won't hurt you, they are totally benign and found in soils all over the world, but still. Kinda gross. So not only can little critters get out, but stuff can crawl in there. Like a pregnant mama cockroach. Its a great place to lay the little roach babies. Or fruit flies let's say?

DIY Cheap Compost Bin

Lucky for us, it's really easy to make a do-it-yourself worm composter that won't have these problems, but is also functionally superior, to the ones you can buy but also WAY cheaper, I’m talking $30 bucks vs $90 for the off-the-shelf ones.

And here it is.


Now I know it doesn’t look super pretty, but what does it matter? It will be living under your sink out of sight, out of mind anyway right? And it's super easy to make. All you need is one of these clear “waterproof” storage containers from Walmart or wherever, some breathable fabric, packing tape, and some cardboard scraps.
And since it is transparent, you can see inside and check on the condition of the compost without opening the box. Also, you’ll notice that when the worms are hungry or bored, they will start getting a little adventurous and crawl up the sides of the box. So you’ll know when to feed them more. You can also monitor the moisture levels by seeing how much condensation is on the sides of the wall. BUT WAIT THERE'S MORE. All this extra headspace helps to regulate the moisture levels, because it will evaporate out of the box when theres too much water, but not so much that it will get the compost too dry like if you had the lid off of this.

You’ll know you got the right kind of box if you look at the lid and can see rubber gasket material. This is what actually seals against the box and makes this “waterproof”. If water can’t get in, the little bugs can’t get out. I got this one at Walmart. Try to find one that has more clamping points since those seal a little bit better.

How to Allow Your Worm Compost Bin to Breathe 

We will need to make sure that the compost can breathe. That’s why the compost bins you buy online have those big gaps. But we can do one better. By using breathable fabric, we are making sure that air can get in but buggies can not get out. I like to use this specific kind of thin breathable fabric called melt-blown fabric.

You can identify it by looking for these little dimples in it. The reason they put the dimples in it is because in the manufacturing process they have the tiny strands oriented in all these different ways and then they melt little dots together to keep it from fraying. This type of fabric is actually made of plastic, which is perfect for our use because the bugs and worms can’t eat through it, its super thin, super strong, and durable. You can find this kind of fabric in some types of reusable grocery bags, some kinds of face masks, or even if you are buying worms online, the bag that they come in, will be made of this material. In a pinch you can take an old synthetic shirt and cut that up. Just make sure that it's made of synthetic fibers like polyester and not cotton.

Start by taking the lid and cutting a circular hole in it. I dunno, about 6 inches round. The exact size doesn’t really matter. I like to take a circular object and trace my hole with a sharpie. After that, just stab the center of your hole so you can get scissors in there and cut it out.

Next take your breathable fabric and cut a square that is one inch bigger than the circle on all sides.

Use some packing tape to tape the breathable fabric over the top of the hole. Press the tape down firmly to make sure it is sticking well.

For extra credit, you can take some vaseline and smear it on the gasket for an extra good seal. I've found that on some boxes, the gasket gets an imprint of this ridge and doesn’t seal as well anymore. The vaseline is an extra barrier to critters escaping.

And that’s basically it! Now you’ll just want to put in some flat cardboard scraps on the bottom to give some breathing room at the bottom and lift the compost substrate off of the floor so that excess water can pool down there.

One flaw of this design is that there aren't any drain holes or any way to get water out of here other than evaporation. Just make sure that you aren’t adding excess water to the compost and you’ll be good. Since this is worm compost, you usually don't need to add extra water like you would with a hot pile compost.

Above the cardboard, you’ll want to add some “browns” as they say, which is really just material that is rich in cellulose. Which is basically like dietary fiber to humans. My favorite to add is coconut coir, but you can also use paper, egg cartons, leaves, mulch, partially decomposed soil, etc.

Once you are ready to put your worms in, add enough water to your browns so that it is damp but not soaked. A good test is to squeeze the browns and see how much water comes out. You are ideally looking for just a little bit of water to squeeze out. If you accidentally put too much water in just add more dry material. Bonus points for using any type of water other than tap water. So that could be filtered water, rainwater, or even tap water that you’ve let sit out on the counter. You just want to make sure that all the chlorine in the water has evaporated out.

Go ahead and dump your new worms in. For a box this size, you’ll probably want 500 worms or so. Give them a tasty treat like some watermelon and let them settle into their new home.

And that’s it! You’re done. If you found this article helpful go ahead and share it with your composting friends, and be sure to connect with us online: 

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