How to Build a Three-Bin Composter

how to build a three bin composter

Illustration by McKibillo

Compost—there never seems to be enough. And if you keep adding material to a single heap, the stuff is never really finished. The solution? A three-bin system that allows you to have different piles in various stages of doneness: You start the pile on one end, move it to the second bin when the first is full and the compost is ready to turn, then repeat, turning compost into the third bin where it finishes. Two people can build our version—which repurposes free wood pallets—in an afternoon.

Tools and materials
7 untreated or heat-treated pine pallets (each 4′ by 3’4″)
1 pound 16d nails

Level a 4′ by 14′ space with a rake and shovel, and stand up two pallets (with the thicker stringer pieces parallel to the ground) to create a 90-degree, L-shaped angle. Nail the pallets together where the top and bottom stringers meet the slats, as detailed above. Attach a second side pallet the same way to create a three-sided, open-faced box. Again hammering in nails as detailed above, attach another back pallet and side pallet to complete the second open-faced box. Repeat until you have three attached, open-faced boxes.

To compost, toss a thick layer of carbonaceous material, such as brown leaves, straw, or wood chips, into the first bin. Shovel nitrogen-rich material, including grass clippings, manure, and kitchen scraps (no meat or bones), on top of the browns and cover with another layer of carbonaceous material. When it has begun to decompose, turn the material into the next bin. Use the now-empty first bin to start the cycle over, moving and turning compost until it finishes “cooking” in the third bin.

Illustration detail, above: Join the side pallets to the back pallets by driving in two nails at 45-degree angles from the rear of the bin at both top and bottom corners.

How to Build a Three-Bin Composter