This year I finally decided to build a composting system to enrich the soil in my raised bed garden. Here’s an assembly schematic for building your own 3 bin compost system. There are a lot of plans on the internet for cheap and supposedly free compost bin systems. This is not that! This is a well designed 3 bin system designed to last for many years and also look nice. I riffed on a design that’s in the vegetable garden area at my local botanical gardens, and I’ve tried to incorporate a few specific features.
First, I wanted something that looked fairly nice and organized and fit with the aesthetic of my garden area. Second, wanted to make sure it got plenty of airflow. And lastly, I needed to keep my beagle, who will eat anything, out of it!
The other thing to note is that I did use ACQ pressure treated wood so that the compost bin system would last a number of years. I’ll say a quick word about that. Prior to the 2000’s, pressure treated wood was manufactured using chromated copper arsenate (CCA), and while there were debates about the potential leaching of the arsenic into the soil, generally speaking pressure treated wood was not recommended. Since that time, the manufacturing has changed to alkaline copper quaternary (ACQ) which is not known to have toxicity issues or to leach into soils. So do you research and decide for yourself whether you want to use pressure treated lumber or not.
At the time of this post (in the midst of ridiculous lumber prices!) the total cost of the completed bin was about $300including wire mesh and hardware.
I’ve also prepared detailed step-by-step instructions for building the bin system on a downloadable PDF for $5 if you’d like a more detailed printed version of the project plan.
Materials List and Diagram
- 2 1 x 4 – 10′
- 2 1 x 4 – 8′
- 9 1 x 6 – 8′
- 4 2 x 4 – 10′
- 12 2 x 4 – 6′
- 1 roll of 1/2″ wire mesh – 3′ x 25′
- 1 box of 2.5″ exterior pocket hole screws
- 1 box of 2.5″ exterior decking screws
You’ll see above that there’s a 1 x 4 and several 5 1/2″ pieces of 2 x 4 that are in gray. I added these as optional pieces to reinforce the bin sides. Over time I’ve noticed that as I filled the bin system up, that the outer sides of the bin weren’t as stable as I wanted, so I added these as “optional” reinforcements, which I’ll indicate on the plan steps. I haven’t actually used them on my bin, but may add them at some point.
Assembly Schematics
Below are front, rear and side views of the 3 bin system with measurements.
As noted above, below are 2 additional views, a front view and rear top view (with the trim hidden), indicating the added front supports. Note that the trim on the two middle partitions will need to be shortened by 3 1/2″ to accommodate the front trim brace.
I’ve also prepared detailed step-by-step instructions for building the bin system on a downloadable PDF for $5 if you’d like a printed version of the project plan.
3 Bin Compost Process
If you’re looking at this plan, then you’re probably already familiar with the benefits of composting. But you may not be as familiar with the 3 bin composting process. It’s pretty simple.
The process was designed to accelerate the breakdown of organic composting matter quickly and consistently by employing a rotation. Rather than continuing to add material to a single pile or bin, you fill up Bin #1, turning the pile regularly to aerate it, then move the entire pile to Bin #2 and start filling up Bin #1 again.
Don’t add any more new material to Bin #2 once it’s been moved from Bin #1, although do continue to turn and aerate it. Keep in mind that the compost material needs to stay moist and you’ll want the internal temperature to average 140°. That kills weed seeds and most pathogens in the soil.
Once Bin #1 is filled up again, move the pile in Bin #2 to Bin #3, and then Bin #1 to Bin #2. Continue to frequently turn the piles in each bin, but don’t add any new compost material to Bins #2 and #3. Let them continue to decompose. New material then gets added to Bin #1.
If all goes well, by the time bin #1 is filled up for the 3rd time, Bin #3 should be ready to augment your garden soil. The compost is finished when most of the original plant materials are no longer recognizable. Finished compost is dark colored, crumbly, and looks and feels like soil.
Here are some additional helpful resources for composting.
- Backyard Composting from the Alabama Cooperative Extension System
- I’ve found Anthony Roebuck’s HelpMeCompost site to be very informative
