Concrete blocks are an inexpensive and versatile material for many home do-it-yourself projects. They're convenient to work with, since they're lightweight enough for most adults to lift easily and large enough to stack without needing mortar to hold them together. If you have a quantity of blocks left over from another project, or have the opportunity to acquire some used blocks from a demolition or renovation, they can be used to make a sturdy compost bin (see Reference 1, page 3).
Measure the site for your bin, and mark it with wooden stakes. The inside of the bin should be at least 3 feet wide and 3 feet deep, which allows the pile to be large enough for the compost to decompose properly (see Reference 1, page 4).
Level the area where you'll stack the blocks, using a shovel and a rake. Lay down gravel, if you wish, to make a more stable base. Remember that your stakes mark the inside measurements of the bin, so the blocks must be stacked outside your markers.
Lay down a row of concrete blocks along the back of your bin, with the open sides facing down and the solid sides facing inward. Make a corner at each end by placing one block at a right angle to the back wall. One of these blocks should be lined up with the rear edge of the wall, and the other should be lined up with one of the sides. This creates a staggered pattern for a stable wall.
Place a row of blocks down each side of the bin site, from the back wall to the front edge.
Start the second row of blocks at one of the corners. Lay the first block so that it overlaps two blocks on the layer beneath, making a staggered arrangement.
Continue the second tier of blocks in both directions, until the row is completed. Start a third row in the same fashion, again taking care to stagger the blocks so that each one overlaps the two blocks beneath it.
Continue this process until you have a horseshoe-shaped enclosure at least 3 feet high to contain your compost (see References 2 and 3).
- Leave a 3/4- to 1-inch gap between blocks to improve air circulation into the pile. Alternatively, keep a supply of twigs, wood chips, sawdust or similar material to sprinkle around the edges of the pile. These materials allow air to penetrate the pile, helping supply its bacteria with oxygen.
- If you're using recycled blocks from a demolition, it's prudent to ensure that they haven't been exposed to any toxic substances that might contaminate your compost and your garden.
Fred Decker is a trained chef and certified food-safety trainer. Decker wrote for the Saint John, New Brunswick Telegraph-Journal, and has been published in Canada's Hospitality and Foodservice magazine. He's held positions selling computers, insurance and mutual funds, and was educated at Memorial University of Newfoundland and the Northern Alberta Institute of Technology.