Compost bins you make from concrete blocks are permanent, sturdy and fairly attractive. You can make one with a minimum of work and expense and it will last many years. Because compost needs time to "cook," or decompose, consider building a bin that has two or three separate composting units. This configuration will allow you to turn the materials from one unit into a neighbouring unit, which will speed the decomposition process. The University of Wisconsin reports that a one-bin unit will cost about £39, while a three-bin unit will run about £71 (based on 2004 dollar values).
- Skill level:
Things you need
- Concrete blocks (8 inches wide)
- Soil or sand
- Metal posts (optional)
Prepare an area for your concrete block compost bin that is in full sun and flat. Also, choose an area where water drains through the soil quickly to prevent overly wet compost, which is called anaerobic. It will smell unpleasant if it is constantly soggy.
Make the ground level by raking it and possibly moving soil or sand to the area. Then check it with your levelling tool.
Set 11 concrete blocks in a square configuration with one side open for a one-bin system, leaving about a ½-inch space between the blocks. Use 25 blocks if you are building a three-bin system. Stack your blocks so the holes are aligned and facing upward.
Drive metal posts, such as rebar, through several of the blocks' holes to stabilise your bin if you want.
Continue adding blocks to the top of the layer below until your bin is the height you desire. To improve the bin's stability, stagger each layer of blocks slightly, taking care to allow for the metal posts if you choose to use them.
Tips and warnings
- You needn't use mortar between the concrete blocks.
- You might need to use half blocks in a multi-bin system: you can split the blocks yourself or purchase half-sized blocks.
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