Monday, October 15, 2012

How to Convert a 240L Trash Bin into a Worm Bin: Large-scale Vermicomposting

A lot of the worm bins that you can buy ready-made deal with very, very small capacity (1kg, 2.2lb of food waste/week max.) In our case, that would have meant that we would still throw away much of our food waste. I'd made a large farm with two very large plastic totes, but the worms were still being overfed. I knew we ultimately wanted to stop trash pickup but was a little hesitant to use our large bin until I was absolutely sure that we had almost no trash. 

Anyway, we were recently able to convert our city bin into a worm farm. I noticed there weren't yet any tutorials on how to do this, so I thought I'd go into a little detail here.

240L seems perfect for our needs, as we eat a lot of fruits and vegetables and only have a tiny concrete space (so no space for regular composting). We're a family of 4, and Eli will just be starting solids properly in the next few months. A few of these might be perfect for a block of flats.

What you need:
  • 240L Bin
  • Tap (we got ours from a beer supply store, nurseries are also likely to have them.)
  • Something to create a false bottom (see what we used below!)
  • Something to filter castings so the bottom mainly has liquid
  • A hatch where you can retrieve the fully processed castings (so you need something to reattach the piece of plastic so that it can open and close. If you look below this will make more sense)
  • Ventilation for the worms. (biggish holes are fine; happy worms don't flee)
  • Red wriggler worms. You can start with whatever portion your bait shop/nursery supplies, and gradually help them to reproduce to scale up the farm. We  started our farm with roughly 1000, now we likely have several thousand.
  • Jigsaw and drill

Worm basics:
  • Worms can stand a fair bit of cold (for example, a unheated indoor space is usually fine, even if places like Boston), but dry out quickly if there's direct sunlight on the bin.
  • Worms like some shredded, wetted, newspaper on the bottom of the bin to help mediate moisture and provide bedding while they're getting settled. A bunch of shredded dry newspaper on top of the food waste will help mediate moisture and keep fruit flies and other bugs away.
  • If you have worms leaving your farm, it's a sign that somethings not comfortable for them (too hot, too wet, too dry, too much onions/orange peels/other.)
  • Once the farm has a fair amount of food waste and worm castings, I've found small amounts of undesired foods (meat, onion peels, orange peels) are fine. 
  • Worm castings are the perfect compost. Really, it's awesome. 

Step 1: Move the bin into a spot where you can work on several sides.
Here's the bin! Eli was observing.
Steps 2 and 3 (We forgot to take a picture after step 2):

  • Install the tap as close to the bottom of the bin as will still work for collecting liquid. It's not hard to install the tap- you can drill a few holes with the largest bit you have, or use a jigsaw to smooth it into a round hole. basically start small and gradually make bigger until the tap squeezes through. 
  • The unfortunate step is that you actually need to climb inside the bin to get the washer/nut fitted from the inside. We'd left the bin to clean and dry for several weeks before doing this, so it wasn't too gross. Wait a second.... if you cut the trapdoor first.... whoa. So you DON'T need to get inside the bin after all!
  • Using the drill and a jigsaw, cut a trapdoor that's big enough for you to get your hand in with a small spade, to retrieve finished worm castings. This is THE major advantage of this system. The worms move upwards towards new food, leaving worm castings relatively worm free, so you're not losing worms when you fertilize your plants. 

The piece of plastic is removed. We used a hinge we had lying around to reattach it.
Step 4: Make some kind of false bottom, so any extra liquid has a way to drain away from the worms.

  • This is where we have to get creative, as I'm not going to suggest buying something and making a shelf in the bin. I happened to find the lid of a laundry hamper lying on the street, and it turned out to be a good fit. The indentation for the wheels holds it up from the floor of the bin. 
  •  The holes on the laundry hamper lid were quite big, and I wanted to find something that wouldn't let too many castings (or worms) through, and that the worms wouldn't eat. I thought these orange bags would be perfect- very strong with relatively small holes.

Step 5: Drill holes in the top third of the bin
  • The number of holes depends on the size of the bit, but for now I'm going with 5 holes on each side, 1cm diameter each. I'll edit if it seems like there's not enough air in the bin. For now it seems great, with the bin about 2/3 full.

Step 6: Add Bedding and Worms!
  • If you're adding worms for the first time, add wet newspaper, followed by the worms with a tiny bit of food (some apple peels or something) followed by dry newspaper.

The worms in their new home. 
There you have it! Let me know if you have questions.

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