My Flow-Through Worm Composting Bin

Nearly a year ago I became enamored with the notion of employing an army of worms to do my dirty work. I was already collecting table scraps, but apartment living made composting those scraps difficult. So, believe it or not, vermicomposting saved the day.

I researched both industrial and hobby sized worm bins. Nothing was exactly what I was looking for. So, I borrowed from various designs and began to sketch my own.

The result was a bin based on the continuous flow-through model which, in theory, allows one to harvest castings from the bottom while worms work their way up through a lasagna of food scraps and wet cardboard. We’ll see how that goes.

The entire bin is elevated, and that’s for a couple reasons. It’s easier on everyone if you can put a collection bin below it for harvesting. Air can also get at the soil a bit easier. And because this was going to live inside our home it needed to look nice. Real nice.

To create these tapers I simply cut the first one out then used it as a master template for the other three.

Speaking of nice, I added fancy tapered legs. I’m handy with a jigsaw… it was the only powered cutting tool I owned for years. The legs flare from 2” to 3” towards the base. It’s a small thing, but it helps to make the entire piece feel like it belongs.

Dowel holes drilled and ready to rock. It takes some upfront prep, but assembly goes fast after this.

This was also my first project using dowel joinery. I’ve never felt the magnetic pull towards a Kreg Jig despite their seeming popularity. At some point I came across the Dowelmax Jr. for $99. Hands down this is the way to go. It’s intuitive, extremely accurate, and a breeze to use with trigger clamps. I’m not a wood working ‘purist’. Though I enjoy the fact that i’m inching closer to pieces that are solid wood.

A drill press made quick work of the conduit rests. Assembly was another story. The real trick is to deepen the conduit rest holes just enough so the metal conduit has lateral play. This allows you to work your way up the ladder and prevent the conduit from falling out.

A flow-through bin is designed to support the soil while also allowing a small amount to be removed every few weeks. I used galvanized steel conduit spaced 1 3/4" apart for the bottom. This is the type of material electricians typically use to shield lengths of AC wire.

At this point i’ve completed two sides. To join them together I needed to assemble and glue the conduit support structure. This needed to happen fast.

Getting to this stage is the reward. I was also impressed by how smooth the assembly went and how ridged the final piece was. Dowel joinery for the win!

Someone at work mentioned that clamps are important when wood working. And I agree — especially when using dowel joinery. At this stage the glue needed to set. I brought the box into square and used whatever I could find to ‘clamp’ the piece together.

I’m not sure if there is a right or wrong way to install hinges. These were cheap and seemed to do the job.

Shopping for hinges is far more complicated than it used to be. I seriously doubt my ability to fully comprehend the articulation of fancy cabinet hinges. These hinges are very simple, and I routed a groove so they would sit flush.

This next step may include the one project decision I eventually regret. I added 1" thick insulation to four sides. I thought this would help keep the worms at an elevated 75–80 degrees. The downside? As food breaks down I may end up cooking the worms. My backup plan is to inundate those chemical and microbial processes with lots of cardboard and other browns.

There are a dozen ways to prepare worm bedding. In my case I placed one piece of cardboard on-top the conduit bottom. This will eventually break down. For now it serves as a temporary floor while the bin fills up. I bought 5 lbs of red wigglers and dumped them on top of 4" of wetted cardboard.

I expect 2–3 months to go by before I can harvest any castings. In the mean time i’m paying attention to bin’s temperature and relative moisture. You want it to stay between 65 and 85 degrees.

Here she is, all done! This guy didn’t waste any time moving in…

I added a few finishing touches. The cedar boards along the sides are lightly sanded but left unfinished. I trimmed the lower front edge so it was swept ever so slightly. And nob on the top makes opening that much easier.