8. The Rotating Sphere Compost Ball
A sphere tumbles more smoothly than any barrel, and it looks almost like garden sculpture sitting on the lawn. You can build one from two large plastic planter bowls, or from a pair of heavy-duty round planters bolted rim to rim.
What you need:
- Two large round plastic planters or bowls of matching diameter
- Stainless bolts, washers, and nuts
- Hinges and a small latch for the door
- A drill and a 1/4-inch bit
Time: 90 minutes. Difficulty: beginner.
Cut a door opening in one half of the sphere, then bolt the two halves together along the rims using six to eight evenly spaced bolts. Line the inside of the rims with a strip of weatherstripping or a bead of silicone so material does not sift out through the seam. Add hinges and a latch to the door, and drill aeration holes in a scattered pattern.
Because a sphere has no flat side, it rolls in any direction, which makes turning it almost effortless — a light push sends it across the grass and back. Keep it out of full afternoon sun if you can, since dark plastic spheres can get hot enough to cook the microbes you are trying to encourage. When the batch is ready, open the door and roll it slowly to pour compost out onto a tarp.