How to make a compost tumbler

Gardening requires a lot of compost. Our previous method was to dump everything in a pile in the corner, never turn it, and hope that it would somehow decompose. It worked, but far to slowly to be useful. So I decided to build a composter.

After some research, I chose to build a compost tumbler because it would save us the time and effort of turning a compost pile every few days. I found a few plans online that I used as guidelines for my project:

The most detailed compost tumbler plans also came with video. This is the design I ended up using.
The instructions from the Boy’s Life magazine were useful for making sense of the cryptic plans.
I also watched other videos on Youtube to get ideas.

Total cost: about $50 per compost tumbler, plus 5-10 hours of work (not counting the 6 trips I made to the hardware store). I made two units because I need a lot of compost.

More detailed steps follow after the jump.

Steps: (for more pictures see my photo album)

Wash the barrel with detergent. Make sure the barrel you get wasn’t used for chemicals.
Cut a hole in the bottom using a portable band saw (best) or a holding a hacksaw blade in gloved hands (what I did). Drill a starter hole first so you can get going. This was very hard work!
Cut the 2×6 inch (mine was 5.5×11.5cm) wood into the correct lengths. Adjust for the height and width of your barrel according to the plans from dixiegrilling.com. My barrels are 24″/61cm diameter and 35″/88cm high, so I cut 2 x 76cm pieces for the width and 4 x 70cm pieces for the legs and upright supports.
Assemble the wood into the base as shown in the plans/pictures. Use screws (make sure you pre-drill appropriate-sized guide holes, a mistake I made) and carriage bolts (for the T intersection).
Cut a notch or make a round hole for the 3/4 inch pipe.
Cut the 3/4 inch metal pipe the right length (total outer width of your base + a few inches extra).
Cut two 7/8 inch holes halfway up the sides of the barrel for the metal pipe to go through. Make sure they are in a straight line. I didn’t have the right drill bit so I used the largest one I had and slowly enlarged the hole.
Cut a hole in the bottom (former top) of the barrel for the 3″/80mm threaded pipe end. Again, I used a drill bit to slowly open the hole up – not the easiest way, but it worked.
Cut the 3″/80mm heavy gauge PVC pipe to the correct length (about 3/4 of the inside length of your barrel). Glue on the cap and threaded end using PVC glue. After it dries, test it in the hole to see if it fits well. You could use a closet flange as listed in the plans instead of the threaded pipe+cap I used.
Cut two 7/8 inch holes in the air pipe at the correct level to match with the holes on the barrel so that the 3/4 inch pipe can easily thread through all four holes. This is very difficult and easy to make a mistake. Measure twice and cut once. I don’t have exact measurements for this because it depends a lot on your pipe fittings and barrel.
Drill hundreds of small holes in the air pipe using a 1/2 inch drill bit. This is hard work – wear ear protection!
Thread the 3/4 inch pipe through the barrel and air pipe holes.
Cut short lengths of 25mm PVC pipe (any size that fits over the 3/4 inch pipe). Test the barrel on the base to see if it rotates well.
Make a lid using wood, plastic, or metal. Mine was made by a local carpenter. I put in nails (you could use bolts) to hold the lid in place inside the hole. It needs to be strong enough to hold up to 100 pounds of compost inside when the barrel is upside down.
Use bungee cords to hold the lid in place while the barrel rotates. If you can’t find long enough cords, you can drill holes in the sides of the barrel to attach them.
Test your barrel for rotation.
You’re done: front view, side view, video.

Fill your compost tumbler with a good mix of nitrogen-rich (food scraps, manure) and carbon-rich materials (leaves, grass, wood chips). I found a helpful spreadsheet for calculating the ratio of carbon to nitrogen (ideally, about 30:1 of C:N). I filled one compost tumbler with leaves, food scraps, and manure; the other compost tumbler only with rice hulls, food scraps, and manure. The internal temperature of the compost should rise to 120-160 F if you got the mix right. Rotate the barrel every 3-5 days for the fastest composting.

metikos