How to Build a 3-Bin Composter for Less Than $5
* This article contains affiliate links. For more information, please read my Affiliate Disclosure.
A 3-bin composter lets you mix in one compartment, turn in another, and store finished compost in another. And you can build your own for next to nothing:)
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I’ve been wanting a compost bin forever.
When we first moved to our property a couple years ago, there was already an old compost pile that had been left sitting for years since the previous owner had passed on. I’m sure there was probably some good soil underneath the grass clippings that covered the top. But we had a lot on our plates when we first moved, so we didn’t really “do” anything with the compost heap aside from add to it.
And add to it we did…
In fact, all we ever did was add to it. I was just happy to have a place to toss our organics on our property.
Before, when we lived in the city, we had no choice but to throw it away until it became mandatory for all buildings to get a green bin. But even then, we couldn’t really benefit from our own organic waste.
Naturally, when we moved to our current home, I was excited at the prospect of starting the garden I had always dreamed of and of using soil made by us to feed all of our plants. But I didn’t know much about composting other than what you could toss in a compost pile. So we just continued to toss.
The following summer, we were too busy putting in our raised beds, getting new soil delivered and having a baby to worry about dealing with the compost pile. We didn’t have a pitchfork to turn it and it was turning into a compost mountain. We knew there was probably lots of fertile, wormy soil buried in there somewhere, but we just had too much going on to get to it, and it was low on our list of yard-work tasks.
By the end of last summer, weeds began to grow wildly out the top of the pile and the bramble had found its way over as well. Our potentially rich soil was now being tainted by awful weeds we definitely didn’t want in our garden!
By the time we were ready to start prepping our soil again this spring, the compost pile had all but completely disappeared beneath the new growth that had sprung up all over it. It’s now less like a pile and more like a hill. Clearly a very fertile hill considering everything that’s growing out of it. But we pretty much decided to just let it go back to nature and start fresh.
In order to start fresh, though, we needed a proper compost bin.
I started bugging my husband, Ryan about the composter more and more this year until he finally gave in and agreed to give up a day on the weekend to build us one. To be fair, he’s always working on one project or another, so the reason it took so long to get to this was simply a matter of time.
Between renovations on this old house, building and repair projects for other people and a plethora of other little side projects he takes on, it’s tough to fit it all in. But we were at a point where we needed this to happen. No more waiting. I couldn’t throw one more slimy banana peel on top of the mountain formerly known as our compost pile and feel good about it.
And so, our 3-bin composter was born.
Ryan did some research on what type of bin he wanted to build and decided on a 3-bin-composter. Having the 3 bins is so much easier than just having one pile because you get one bin to toss everything into, another bin to mix it and turn it into compost, and a third bin for finished compost that’s ready to use in the garden. Already a much better plan than we had ever had before.
We also wanted to make our bin completely out of free, recycled materials if possible. Since we live in an old house that’s under constant renovations and are of the homesteader mentality that materials should be stockpiled for just this purpose, we just so happened to have everything we needed right here on our property:)
We used wood from old pallets and fir siding and shiplap that were a by-product of the renos. Then Ryan found a piece of corrugated plastic in the lean-to by the garage which he figured would make a perfect lid. So even though we weren’t originally planning to put a lid on the bin, we decided to add one and actually based the dimensions of the compost bin on the measurements of the piece of plastic.
The corrugated plastic piece was 2 ft. x 8 ft. So we decided that our bin would be 8 feet long and 2 feet wide. As far as depth, we decided on 2.5 feet deep since that seemed about the perfect depth to hold a significant amount of compost while still not being too high to get a pitchfork in there and work it. And actually, Ryan being the talented handyman that he is, decided to make the front panels removable so that we can actually remove the front of each section in order to turn and shovel the compost in and out.
For the lid, he built a wooden frame to go around the edge of the plastic so that it would keep it from warping and give it just a little weight. He fastened the lid with some hinges from old doors in our house and then attached a piece of aircraft cable he had laying around to the lid and the side of the bin so that when you throw the lid up and back it doesn’t fall back too far. We were going to use a piece of wood to prop the lid up like you would with the hood of a car, but this was more practical.
As for tools, we used…
- a reciprocating saw to cut down the pallets. (This saw is also known as a “sawsall” because it pretty much saws all things you could need to saw. It even saws through nails, which was especially handy when sawing boards off of pallets).
- a table saw and a sliding miter saw to cut pieces of wood down to size,
- a drill/impact driver to piece everything together,
- a crown stapler for part of the lid, and
- a good ol’ fashioned hammer to remove some of the harder-to-get-out nails from the pallet wood.
All said and done, we completed the compost bin from start to finish in one day and it cost us less than the price of a packet of seeds. The only non-recycled material used were the construction screws we used to put it all together:)
If you factor in the cost of the power tools, that would certainly add to the price, obviously. But since we had all the tools we needed already, the tools were already paid for and have proven time and time again to be a wise investment for folks like us!
(I’m a firm believer in investing in quality things that will last a long time and save money in the long run by costing less per use. Good quality tools are definitely one of those things:)
And speaking of investments, after investing some hot, sweaty work on a beautiful, sunny, Sunday afternoon, we now have a sweet as compost bin that will surely last us a very long time and help us to produce some amazing, fertile compost to feed our garden with for years to come.
It’s official! We’re real gardeners now:)
3-Bin Composter Building Instructions
Below are full instructions on how to build a compost bin like the one we did. Keep in mind that you can amend your bin or design based on the materials you have on hand, so don’t feel like you need to follow the instructions exactly.
If you don’t have a piece of corrugated plastic to make a lid out of, you could use tin roofing or even a piece of plywood. Or you could forgo the lid altogether if you like! (In fact, you’ll want to leave your lid open at least sometimes when it’s raining so your compost gets watered. Water helps the organic material decompose:)
If you don’t have pallets but have other pieces of wood long enough, use those! Or if you would rather buy wood new, go for it! We just like to do things as frugally as possible whenever we can.
And you can change the dimensions as well if you would like it bigger or smaller (or you need to adapt your own bin to the measurements of some materials you are using). But personally, the size and dimensions we went with seem pretty perfect to me as long as you have the space to put it.
The point is, feel free to substitute any materials that you have on hand that would work in place, and alter the size or the design if you like as well. However, in order to replicate the 3-bin composter that we built, here are the instructions:
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Step 1: Prepare Design and Materials
1. Prepare your design and measurements. Here is our design:
2. Gather all materials you will be using. Make sure you have enough wood to work with. If you have piles of scrap wood laying around like we do, gather all pieces you think you can use.
When using scrap wood it’s difficult to say exactly how much you’ll need, but in our case we used the wood from two pallets, two 10 ft. 4×4 posts, and at least 20 shiplap boards, approximately 4 to 5 feet long, plus a bunch of odds and ends. We then milled the lumber we had to the correct dimensions in our schematic, which we’ve included below.
* Note: If you don’t have scrap wood laying around, you could purchase new lumber, or you could get some free pallets from any big warehouse store. Big box stores always have more pallets laying around than they know what to do with, and are usually happy to give them away for free to anyone who will take them off their hands.
3. Prepare tools and inventory materials (in our case, that meant setting up the power tools, breaking down pallets with a reciprocating saw and stacking materials together).
Step 2: Assemble the Sections of the Bin
1. Cut lumber for the main panels, which will make up the three sections of the compost bin. We used two 4×4 posts cut down to 30”, and six boards cut to 26” -a mixture of pallet boards and shiplap cut to size- to build each panel. We built four panels in total, which made up the two outer side walls and two inner walls that would separate the 3 sections of the compost bin.
2. Assemble panels. We made sure to leave about an inch and a half of space in between each board to allow air to flow through the bin and aerate the compost. (Fig. 1)
Step 3: Assemble the Back of the Bin
1. Once you’ve assembled the main panels, stand them up and space them out according to how wide you want each section of the bin to be (this might be easier with some assistance, but our panels stood up pretty well on their own). Stand your two outer panels up 96” apart if you’re using the same measurements as us, and then place the two inner panels in between to separate the sections of the bin.
We decided to make the first section larger than the other two because the first section of our bin was the one we would do all the mixing of our compost in. So we made the first section 36” wide and each of the other two sections 30” wide. (Fig. 2)
2. Tie all boards together by attaching boards to the backside of your bin. Ideally, you would have boards long enough to run the entire length of the compost bin, but if you’re using smaller or varying sizes of scrap wood like we did, you can cut boards down to the length of each section to fill in the backside.
Step 4: Build Channels for the Front of the Bin
1. Create channels on the front of each of the 4 posts. The channels will hold the boards in place that will make up the removable front panels. This is best done with a table saw, so if you’re using hand tools you might want to forgo being able to remove the front panels of your bin. If so, you can just attach the boards the same as at the back, using some construction screws or nails.
To create each channel, first cut filler strips by cutting a 30” piece of wood (we used a piece of 2×6 board), and mill it to a thickness just slightly thicker than the boards you’re using for your removable panels. We used shiplap for the removable panels at the front, so we milled our wood to just slightly thicker than shiplap, or about one inch. Then cut a 30” cover piece for each channel.
Use a board that’s at least as wide as the post or preferably a bit wider. Attach a filler strip to the centre of the front of each post. Then, attach a cover piece to each filler strip. Attach them in the middle so that the gap in between the post and the cover piece creates a channel for boards to slide in and out of on each side of each filler strip. (Fig. 3 + 4)
2. Cut the boards that you’ll be using for your front panels down to size. Measure the distance from one channel opening -filler piece to filler piece- to the next. Cut boards to that length or just slightly less. Slide your boards into place to complete the front of the bin.
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Step 5: Build and Attach the Lid
1. Use whatever material you’re using for your lid (if you’re adding a lid), and attach it with a couple hinges to the back of your compost bin. Old door hinges are a good choice because they can handle the weight of a lid. Then attach a piece of chain or aircraft cable (which we used) to the lid and one side of the bin so that the chain or cable prevents the lid from opening too far back.
Last Step: Stand back and marvel at your work!
You now have a brand new composter:)
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