The project: My mother-in-law had long expressed interest in composting her food scraps, but didn’t care for the plastic bins available for purchase. I’d been interested in building such a bin by reusing salvaged lumber, mostly discarded wood pallets. This presented a fun challenge: construct a compost bin that satisfied her aesthetic requirements and followed my principles of reuse.
It turned out well: it’s attractive (in a rustic way) and functional, though took longer to build than I expected. Breaking down pallets was a big chunk of that time overage: they were free in monetary cost but not in the time they took to process.
Design: I built it probably a little too big, 32″ L x 30″ W x 29″ H. Compost bins have to solve for the problem of emptying the finished compost (after a year or so) while leaving in place any recently-discarded food. In bins like this, which will be emptied via a not-yet-installed door in the bottom of the side (see below), that separation is achieved by the depth of the pile. The bottom of the pile, with older finished compost, is no longer turned, while the fresher, unfinished material rests on top. In a narrower bin, the walls support layers of material such that the top layers can be left in place while the bottom is scraped out. This bin may be too big to neatly do that. Perhaps the over-sizing just means it can go a few years between emptying.
The slender buckthorn log on top was a last-second addition. It supports the lid in its open position so that the hinges don’t bear the door’s full weight. This bin is lovely and robust, but maybe overly complicated for task of turning food scraps into soil. The next bin I build may be much simpler, left unfinished and entirely open to the air with no lid to exclude animals.
Materials: In addition to many mismatching pallets, I used scrap 2x4s and plywood, plus fasteners and hinges I had lying around. To preserve the wood somewhat, while keeping it food-safe, I treated the wood with mineral oil and some stale cooking oils.
Breaking down the pallets into boards was a learning experience. I found that filleting them with a Sawzall was fastest. Expect to shed bits of nails wherever you work and choose a workspace accordingly. I also should have set a higher bar for the quality of pallets that I scavenged, as I wasted time freeing some boards that were unusable.
Build: the construction was straight-forward. I screwed together 2x4s to make the posts, cut and installed the pallet boards to make the sides, framed out the top and the lid, installed the lid. Remember to leave a gap at the back of the lid panel so that the edge can rotate up when the lid is opened.
Installation: I used a post-hole digger to install the bin, sinking the posts in place. After a few weeks of use, it appeared that an animal had accessed the bin by tunneling a small hole in the dirt under one wall. So I dug a 10″ trench around the perimeter and inserted sheets of metal hardware cloth in the trench, fastening it to the posts that were sunk in the ground. That was it for animals; the lid is too heavy for a raccoon and there are no bears here.
What’s next: Still left to do is installing a door in the bottom of one side. Then, in a year when the bottom layer of compost is ready to be emptied, I’ll scrape out the finished compost through that door. I plan to secure the bottom few boards to each other with wood strips, then unscrew their ends from the posts they’re attached to, and install hinges so that those boards can swing up together. (And add a latch to secure the door).
To spread out the time required by this project, I didn’t build the emptying door before putting the bin into use. Aside from having to work with compost-covered boards, we’ll see if I’ve failed to consider any mechanical problems introduced by postponing this feature.
I reserved some extra pallet slats, assuming that some wood will decay with time/ I should be able to swap in new pieces as needed to keep the project going. I’d be pleased with a lifespan of 20 years for this bin, after which it too can become compost. Planning the eventual obsolescence of a project is new for me; perhaps I’m thinking more timefully.