In-Ground Concrete Worm Bins

At Good Cheer we do a good job of following the three R’s: reduce, reuse, and recycle. Thanks to our worm bins, we are now a zero-food waste Food Bank! We feed our red wigglers overage supermarket rescue and food scraps from the kitchen. The worms turn this food, which used to go into the dumpster, into a beautiful, dark, nutrient rich soil amendment. In fact, we consistently get the Merit Award Blue Ribbon at the Whidbey Island/Island County Fair!

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We love to compost! For our roughly .4 acres of garden space, we have 11 cold compost bins, and 8 in-ground worm bins. Our worms bins are hands down the busiest form of compost in the garden–the worms are fed twice a week during the summer, and produce many cubic yards of worm castings for us.

For the first few years, Good Cheer utilized in-ground wood worm bins. This year, we have expanded our capacity by installing four in-ground concrete worm bins. We love our new worms bins so much, that we thought we could share some instructions and lessons learned with the home gardeners who read our blog! Our materials lists and instructions apply to 4 concrete bins that are roughly three cubic feet. These instructions can be adapted and changed for the home gardener though.

Materials list:

– Cinder blocks (we used 4″, but recommend 6″ or 8″)
– 4′ rebar
– Wooden shipping pallets
– Metal roofing
– Concrete mix
– J-bolts
– Decking wood
– Shovel
– Pick-ax
– Level
– Construction triangle
– Door or window hinges
– Screws
– String
– Power drill

1. Dig a hole. It’s helpful if you have volunteers and/or apprentices for this part!

2. Try your best to level and smooth the earthen walls of said hole, and attempt to make the hole as square as possible. We used flat shovels, hard rakes, a level, and a construction triangle to do so. We even attempted to utilize the Pythagorean Theorem and string to try and mark out a perfectly square hole. Here is a description of how to use the 3-4-5 Rule (an adaptation of the Pythagorean Theorem that is often used in construction) to make square corners. Stakes and string will ensure a straight line to follow when laying the bricks.

3. Lay the cement blocks in the “running bond” or “stretching bond” manner: the blocks are staggered with half blocks. We did a version of this using using 8″ and 4″ blocks. Instructions from Mother Earth News about home brick laying may clarify the instructions.

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4. Drive 4′ rebar through the holes of the cement blocks into the soil.

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5. Place a slatted barrier to section off the bins. This barrier serves both us a means of supporting the walls so that they do not bow in when tamping the soil down, and also to distinguish between worm bins. The wall between the worm bins should have slats that the worm can crawl through to get to new food or to expand the population. We used shipping pallets because we had them in abundance, and it was not too difficult to cut them down to size.

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6. Secure a roof that will both keep critters out of the worm bins, and keep rain off.

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We did this by cementing j-bolts at various intervals along the worm bin. They we drilled whole through decking materials, and attached the frame to the j-bolts. Next we cut a piece of wood to run along the back the allowed for the roof to have a slant, and cut a triangle to block animals from coming in the sides. At first we used re-purposed Trex, but found that the material quickly warped. Wooden decking material cost us a little more (the Trex was free!), but saved us a lot of time and energy.

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Finally, we used some small hinges to attach metal roofing.

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Check out our slideshow for more images of the process!

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