Building a functional compost bin from reclaimed wooden pallets is a cost-effective and environmentally friendly way to manage yard and kitchen waste. This simple do-it-yourself project offers a sturdy structure that can be assembled quickly. The uniform size and shape of the pallets form the walls of the composting chamber, providing an ideal environment for organic material to decompose into nutrient-rich soil amendment.
Selecting and Preparing Safe Pallets
The first step involves safely sourcing and preparing pallets, as not all wood is suitable for composting. Inspect the pallet for a stamp indicating how the wood was treated for pests during shipping. Look specifically for the “HT” stamp, which signifies the pallet has been heat-treated, killing pests without chemicals.
You must avoid any pallet marked with “MB,” as this means it was treated with methyl bromide, a toxic pesticide that can potentially leach harmful chemicals into your compost. Once you have secured heat-treated pallets, wear gloves and safety glasses to inspect them for loose or protruding nails and splinters, removing any hazards before assembly begins. If any pallet boards are broken or missing, repurpose wood from a spare pallet to patch the gaps, ensuring the final structure is sound.
Choosing the Right Bin Design
Before starting construction, decide on a design that matches your composting goals and available space. The simplest option is the single-chamber bin, which typically requires four pallets to form a square enclosure with three fixed walls and one access door. This design is excellent for smaller yards and for cold composting, where material is added over time and allowed to mature without frequent turning.
A more efficient option, especially for active or “hot” composting, is the multi-chamber system, often built with three bays that require seven to nine pallets. This setup allows you to manage materials in three distinct stages: a new collection bay, a middle bay for active decomposition, and a final bay for cured compost. The three-bay design enables the easy turning of materials by moving the contents from one bay to the next, which aerates the pile and speeds up decomposition.
Step-by-Step Assembly Methods
The assembly process begins by preparing a level surface where the bin will permanently sit, which is necessary for structural stability. For a single-chamber bin, stand two pallets on edge to form a corner, ensuring the slatted sides face inward to contain the compost. Secure these initial two walls together using heavy-duty exterior screws, drilling through the solid corner blocks of the pallets to create a strong joint.
Alternatively, use robust materials like thick wire or heavy-duty zip ties to lash the corners together. This provides flexibility and makes the bin easier to disassemble if needed. For a multi-bay system, start by securing the three back wall pallets in a line, then attach the dividing pallets perpendicular to the back wall to form the shared partitions. Corner brackets at the top and bottom of each joint provide extra reinforcement, especially if the bin will hold heavy, wet material.
The final step is creating an accessible front panel or door for adding material and removing compost. For the single-chamber bin, the fourth pallet can be attached to one side wall with sturdy hinges to create a swinging door. Install a latch or a hook-and-eye mechanism to keep the door securely closed when not in use.
Creating a Removable Front Barrier
Another effective method for the front is to create a removable barrier using vertical slots where individual planks of pallet wood can slide in and out. Achieve this by screwing two vertical two-by-two pieces of lumber to the front edges of the side walls, spaced slightly wider than the thickness of the pallet planks. This removable slat system is useful for multi-bay designs, as it allows you to access the compost from the bottom when ready, without disturbing the material above. For added stability, run a treated two-by-four across the back of the structure, securing it to the vertical supports of the pallets.
Siting the Bin and Starting Your Compost
Once the structure is complete, the bin should be placed in its final location, ideally on bare, level ground to allow beneficial soil microorganisms and worms to migrate into the pile and aid decomposition. Placing the bin away from structures and fences is advisable to ensure good air circulation and prevent moisture buildup. Securing the bin is important, which can be accomplished by driving wooden stakes or lengths of rebar into the ground through the corner voids of the pallets.
While partial shade helps prevent the compost from drying out too quickly, some sun exposure is beneficial to maintain the internal temperature required for faster decomposition. To begin composting, start with a foundational layer of coarse, carbon-rich material, such as straw or dry leaves, to promote drainage and airflow at the bottom. Subsequent layers should balance “greens” (nitrogen-rich materials like kitchen scraps and grass clippings) with “browns” (carbon-rich materials like shredded paper and wood chips). Maintaining a consistent moisture level, similar to a wrung-out sponge, is necessary for microbial activity. A simple cover, such as an old tarp, can be used to regulate rain exposure and retain heat.