Double-Decker Drum Composter

Composting is easy and fun. Kitchen scraps, leaves and lawn clippings are allowed to decompose naturally and they become a healthy, nutrient-rich and beneficial soil for the garden.

In this instructable, I will show how I made a spinning double drum composter to make soil for my garden.

Step 1 Making the frame

I decided against documenting every step with building the frame, mainly because it's a simple enough design.

The frame consists of 3 pressure treated 4x4's and 1 pressure treated 1x4, all eight feet long. One 4x4 was cut exactly in half and the 1x4 was cut into quarters - they were to become the 2 beams and 4 stakes.

I drilled pilot holes through the posts and into the beam and held them together with galvanized lag bolts. Each of the corners where the beam meets the post got corner braces and the top got flat braces. The braces are meant for extra support, since the barrels may become heavy. The space between the top beam and bottom beam was 3 feet.

I used a 2 inch hole saw to cut holes into sides of the posts so they can hold the poles later on.

Then, I used some exterior screws to fasten the stakes to the bottom of the posts. The entire frame gets cemented into the ground later and the 4 stakes offer additional support to the frame.

At the bottom of the posts and stakes, I drilled some screws partially into the wood to hold them into the cement better.

Comments

[racoontnn]

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[Lorddrake]

when the barrel is filling up do you have any problem with distortion around the holes that the axle passes through on the barrels?

if so. would it help adding a support plate inside and out (say 6-8 inches square) so that the axle passes through ... plate | barrel wall | plate .. to help redistribute the load?

[iPodGuy]

I never had problems with the axle holes distorting. I just went and looked at the bottom barrel (the one I use the most) and even though it's been four years since I published this instructable the axle holes have not warped or bent. They're smoother obviously because they've been rotated on the axle so many times, but it doesn't appear that they've grown any bigger.

55 gallon drums are really strong.

If you're really concerned with your barrels becoming too heavy and failing, you could always add some kind of plate as re-inforcement. If you have an extra drum, I bet you could cut out plastic reinforcement plates, or wood, metal, pvc... It's certainly not going to hurt the design.

Good luck!

[modrod]

Great Instructable. Last year I expanded on the concept and made a three-barrel, rotating composter where each barrel spins independently and the entire unit rotates to make unloading more easy. I'm still perfecting it and have learned a few things: If an empty barrel ends up on top, it takes a big effort to rotate the two full barrels to the top. I'm thinking of some sort of crank device but with at least two of the barrels cooking at any one time, it's difficult to do that kind of work to the unit. Still works quite well.

I started with lots of air holes, which proved to be too many for our desert climate, so I filled most of them. The down side to that was that during our very wet winter (unusual) the compost batches got too wet and stopped cooking for a while. Now that it's dried out somewhat, everything seems to be working well again.

[forest dancer]

do you have plans for this anywhere on the web? I would love to build one

[modrod]

Not really, just some rough sketches I made based on the original, double decker Instructable and other ideas. The only differences between mine and the double are the main axle and spokes, which are welded to a small piece of tubing at the center.

Sorry I don't have more. I didn't take photos as I went along, so in order to do a Instructable correctly, I'd have to build another one. That isn't feasible at the moment.

[modrod]

Just a quick update on my knockoff. Yesterday, one of the individual barrel axles broke, due to being rusted. I didn't use galvanized to go through the inside of the moist barrels, just some steel tubing I had left over from other projects. It's the bottom barrel in the photo. I'm now in the process of replacing that one and the other two. Other than that, it still works great.

On the spinning issues, I've found that making sure all barrels are full, at some stage of compost, really helps when turning the whole thing.

[rhodge-1]

Gear the main shaft with a Large gear and the drive gear (or two) from a gear speed reduced motor that is fairly cheap at about $50. that will turn those on a 1/3 hp or up to 1./2 hp with all full.
About a 10 to 1 ratio maybe?
I got one of those second hand for $10. Was 1/2hp.

[modrod]

Interesting idea but a little overkill for this application. I've found that my rotation problem goes away if I just keep all three barrels full. :)

I have discovered that iPodGuy's original design for the doors is better than what I did. The plastic doors, at least one of mine, has warped a bit and I'll have to reposition one of the locks in order to get it to seal better. Not a big deal...

[rhodge-1]

For the doors warping; I had occasion to put steel strap around the plastic of one I made years ago and that stopped the plastic warping; used Pop Rivets with inside washers for that.
Maybe add slide screen locks at a couple of other points to spread the load to stop materials pressing outward too hard? What do you think?

[modrod]

That's probably a good idea on the steel strap. Thanks for that for future reference. I do have two slide locks per door and will either move the one that doesn't line up or add another as needed.

[aje127]

Dude that is AWESOME. I have a huge yard that has a BIG veggie garden and then an insane landscape flower and fruit garden. I would be really interested in how you did this and if you fixed your rotating issue.

[modrod]

Nope, haven't addressed the rotating issue yet. I've just been man handling it. I did recently empty out one of the barrels and rotated everything around. Didn't seem so difficult this time, maybe because the bins weren't really overly wet at the time.

[iPodGuy]

That thing is nuts! Nice work!

[BengalTigger]

Here is my take on the dual-barrel setup -- a side-by-side. I bolted a 1-1/4 flange on each end of the barrel (flat side out), with PVC pipe adapter screwed inside and PVC pipe running between them as a bushing, and short pieces on the outside as spacers. I ran a single 1" galvanized pipe through the posts and both barrels.

[Allen Cham]

This is so neat! Ipod Guy, do you think its a good idea for me to put some super dry soil in it too so it fertilizes the soil? Did you need any earthworms or anything like that? and also, do you fill the whole barrel fully with compost or only half full? and is it hard for you to transfer the compost from the top bin to the ground since the lower barrel is in the way?

Sorry its like a whole barrage of question :) great job!

[leander37]

For an extra $25 or $30 I'd consider getting an extra drum and cutting a door that would be oversized as compared to the opening. This might alleviate fit/warp/sticking issues.

[iPodGuy]

That's a mighty fine idea.

[leander37]

The number of holes seems excessive IMHO. I would be worried about compost drying out. When I build this, I'd think about cutting the number of holes in half. Any thoughts?

[iPodGuy]

Definitely go with less. You can always drill more later if the compost is not breaking down properly.

Half of them clog anyway.

[Layout]

My grandfather once made a similar design out of a metal drum. He cut the door out of a second drum and made it larger than the opening. That way you only need two hinges and a latch and the door still holds its shape. Plus it is much easier to open than 4 barrel locks. Great Instructable.

[leander37]

Metal is a good idea, but be careful about what was previously in the drum (oil? pesticides? bleach?), and also consider rust as a potential issue.

[SGravel]

A PVC "sleeve" around any type of metal pipe would solve the problem of potentially leaching contaminants into the soil. It’s an extra step, but you’ll get the best results combining the two materials.

[leander37]

Oddly, PVC may be more "toxic' than any metal that might be used. Steel is predominantly Iron, which is generally beneficial in soils.

[jschmadeke4life]

do any liquids drip out of the holes during the decomposition process?

[iPodGuy]

Yes, lots.

[AlaXul]

I was wondering if the " tea " is good for anything or is it simply waste? Stands to reason that it would have nutrients in it, so add water and water the plants with it. Am I way off base?

[rhodge-1]

Try a base to hold a 1/2 barrel under one; a sloped surface of what is available to you to drain it to one side into a basin /barrel to collect it. Very good to fee plants with as a watering can tea.

[iPodGuy]

Yep. Water it down and feed your plants.

[aje127]

That is BRILLANT. question thou, I don't compost as of yet, so I have no idea how its done, but it is on my list of things to do this year. When you spin the barrel, are you just grabbing the barrel and pulling on it, or are you grabbing the pipe that is running through it and turning that? Also, I'm sure these things get heavy when full, will the area the pipes run in and out of hold up to the weight? (will it rip or tear the plastic?). I love this idea.

[iPodGuy]

I turn only the barrel. There is a lip on the side that I can grip. You could also add extra handles. Once you get a good turn, centrifugal force takes over and I can spin it with little effort.

It does get heavy, but the thick plastic on the industrial grade barrels does not rip or break. It will hold as long as you use strong pipe.

[rhodge-1]

I strongly advise the use of 1/4" hard aluminum /stainless steel plates at the holes for the pipes as bracing and to alleviate the stresses on the plastic for longevity, using flanged self centering bearings of pipe size would make it a Lot easier to turn as will. Add a sprocket from bicycle wheels and a crank will turn Both barrels at one time. Near ground up 45 degree braces would aid stability under use a lot as well; likewise steel plates for house construction timbers will do it too at the top corners.

[Pizzapie500]

If this was only a one barrel composter, can you put fins onto the barrel so that if it's windy the fins will catch the wind and spin the barrel? Like a turbine?

[iPodGuy]

Maybe in a hurricane!

I would say that you would most likely need humongous fins to generate the centrifugal force needed to spin the heavy barrels.

I guess you could use a smaller turbine and a set of gears to try and rotate the barrels. I'm sure somebody could figure that out, unfortunately that somebody isn't me.

[Pizzapie500]

http://www.instructables.com/id/Wind-powered-Composter/

They did it but it's VERY SLOW!

[Pizzapie500]

Really? I thought they would move easily. I'll probably try it out anyway.

[Pizzapie500]

Would this work in the winter?

[iPodGuy]

You could leave it outside in the winter, yes. However, the colder weather may slow down decomposition or stop it altogether.

With mine, everything just freezes until spring. Then it thaws and starts back up again.

[Pizzapie500]

Oh. I guess I shouldn't make one right now since it's below freezing in the morining.

[brandonne]

You might want to paint those barrels. My brother works as a river guide, and their boats are blue because it doesn't get as hot as any other color. I'd be curious to try a test, paint one black, leave the other blue and see which one gets hotter.