Pentagon Composter




About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific...

This is the simplest and quickest compost bin to build.
The necessary materials can be obtained for free anywhere.

I designed this with The Pentagon in mind, as a way for our armed forces to deal with their organic waste without burning or trucking it, both of which expose our troops to harm.

Setup and knock down is very quick and easy.
This composter will eventually compost itself, which is a good thing, since it's made from waste materials and is so easy to build.

Want your compost quicker? Try a Compost Tumbler

Step 1: Gather Materials

It took me about a minute to find the materials in our dumpster area here on the base. Here's what you need:

5 identical wooden panels. If the ones you find are too big or small, cut them down or nail on another section. I found some 40" wide chunks of weathered plywood of varying lengths from packing crates. Don't use pressure-treated wood. For anything.

Rope, cord, or wire. I found a 20foot chunk of polypropylene rope and some smaller pieces of polypropylene rope.

Paint: Optional. Since my composter is intended for the military I chose olive drab. Since I'm on a former military base which is now a superfund site, all the military shades of paint are very plentiful in orphan piles.

Step 2: Trim the Panels

The plywood I found was pretty rotten around the edges so I pulled the nails and sawed an inch off three sides. Then I scored each panel at the same height and sawed them same.
I ended up with five panels 37" (about one meter) square.

The dimensions are not critical at all. Make yours big enough for the quantity of compost you'll get, or to fit in the space you have available.

Step 3: Drill Holes

Drill two 1" (~25mm) holes in each side edge of each panel.
I stacked them up and drilled them all at once.
The spade bit, usually my favorite, didn't work well.
The rotten wood fibers wrapped around the edge and clogged it.
A different bit with a feed screw at the tip worked better.

Compost needs air to decay properly. If you want more air to get to your compost drill more holes in the sides.

Step 4: Paint - Optional

Paint is optional. Think about whether you actually want to paint it.
This composter will eventually compost itself and join your soil, your food and your own body.

I chose Olive Drab (O.D.) so as to not give away the position.
Choose the camouflage pattern that matches your terrain.
"Dazzle paint" would be great for a marine setting.

I found an orphan can of O.D. latex paint and slobbered it all over the panels with a roller and a small brush for the inside of the holes. I painted both sides which is totally unnecessary, but coffee demons made me do it.

Get a real paint lid pry-tool from your nearest paint store and don't mess up the lip of the can. That way it won't dry up in the can so quick.
I'm a big fan of misusing tools and adapting one thing for another, except for those paint can tools. Don't use anything else for that. Get the real tool. It's free.

Step 5: Deploy

Set up the panels leaning corner-to-corner like a house of cards.
Tie the corners together with cord or wire. I used my long piece of cord running it through all the upper holes.

I tied the ends together with a "trucker's hitch" and drew the cord tight.

Step 6: Compost Away!

I put an oyster mushroom starter in my composter to help break down hydrocarbons and other chemicals. There are a lot of such chemicals spilled here on the base from fueling and maintaining aircraft. JuniorLee gave me the mushroom starter from a project she worked on in New Orleans after the disaster.

Your compost needs air and water to work properly. It doesn't need to be soggy, but make sure your compost doesn't dry out. It will get hot from decomposition and that will tend to dry it out. Soapy water or rainwater is fine.

If you want to keep animals out of your compost put a weighted board or chickenwire over the top. If they're very motivated you may need to nail chickenwire around it and set it on chickenwire. Depending on what the animals are you might not care. Their guts will break down the plant matter faster than anything else.

If you want to compost human manure, read the book Humanure Handbook. You'll want at least two composters so you can let one sit inactive for several months after the last addition before dumping and spreading it on your garden.

Step 7: One Year of Evolution Later...

I've moved the composter onto a pallet so it can be moved with a forklift.
It's now square so it could fit on the pallet better, and so the fifth wall panel can be used to cover it in the rainy season.

The compost was getting way too wet in the rainy season. So it needed a lid.
Some years we get all our rain in three months, and then we don't get any rain at all for six months.

In the rainy season and right afterward, the grass and weeds grow like crazy. We get a lot of grass clippings and weeds to compost. In the dry season there was a watering ban, and everything turned brown and stopped growing. So then the compost began to be mostly food waste. There was a thriving worm colony in the compost, but they couldn't keep up with the food waste. That led to fly and smell problems. It was located right under some open windows. That wasn't good for the people inside the windows. So the compost needed to move away and to get mixed more.

I've just added a Compost Tumbler as a first stage composter..
I'll probably add another square bin so there'll be a convenient supply of old compost for gardening and for adding to the fresh compost.



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    14 Discussions


    9 years ago on Step 7

    I like your style. You should be in charge of a lot of stuff.


    9 years ago on Step 4

    My only concern with paint is if any chemicals would leech off the paint into your compost. I'm not sure if that would happen or not, though, so maybe I'm just worrying about nothing...

    Black Ethel

    10 years ago on Introduction

    My landlord wants us to use a compost bin and not just heap the compost in the corner of the backyard. But compost bins are not cheap and I'm not especially handy. This is the best and easiest way to make a compost bin I've ever seen...THANK YOU! :-)


    Reply 11 years ago on Introduction

    Somebody's up just a little too early... :-P Interesting shape for a composter tho...


    Reply 11 years ago on Introduction

    Ah, I thought that the time stamp was for the posters local time, not the time in California...learn something new every day. Let's see, I'm in Ohio, which is 4 hours ahead of California and my friend in England is 5 hrs ahead of me...soo you're 9 hrs ahead of California meaning it was midday at the time of the post (if my numbers are right, about 1:40p) meaning the kookiness of the comment probably wasn't from sleep deprivation. Crazy Brits! Just kidding of course... Aside from my pastime of poking fun at the British (all in good fun of course!), I'm working on an instructable for a kite made in grade school awhile that I believe worked by the magnus effect that I surprisingly haven't spotted anywhere on the interweb highway (if I wasn't so lazy I'd have it done) and while that is completely off topic (apologies to the author) you're name is, after all, Kiteman so I thought you may be interested. Crap, now that I've told you about it, I need to finish it...


    11 years ago on Introduction

    I imagine old pallets would work well for this. They are about the right size. You would benefit from the additional air circulation. Critters could be a problem but you could surround with chicken wire. However, there would be no need to cut or drill holes. My mother usually just made a mound directly on the ground without any sort of covering. It worked like a charm. I can still remember the steam that rose from it in the winter.


    11 years ago on Introduction

    I need another compost bin. Maybe I'll try this, although my technique seems to be a lot simpler. I just take a big plastic garbage can with a few holes drilled in the bottom and fill it up with food scraps until it's filled to the top. When it's full, I cover the food scraps with a few bags of free used coffee grinds from starbucks and then plant some sort of plant in the grinds. When I harvest whatever I'm growing, the compost is normally nice good dirt by then...


    11 years ago on Introduction

    Smart idea, it looks very cool, and looks very easy to do, great job.


    11 years ago on Introduction

    I would just switch the rope to a hemp or natural rope.
    Also the paint to an oil.
    Just to make it 100% decomposable(A.K.A. Plastic rope=bad)


    11 years ago on Introduction

    i like your reason for doing this and it looks like its really easy :-) good job and very easy to understand!