DIY Compost Barrel Tumbler
It's large and loaded with features, but you can build this compost barrel for the cost of a bargain model.
IntroductionDrum composters convert yard waste to finished compost much faster than stationary compost bins do because they allow you to churn and instantly aerate the waste. Plus, drum composters are easier on your back.
- 4-in-1 screwdriver
- Cordless drill
- Drill bit set
- Miter saw
- Pocket hole jig
- Rivet gun
- Safety glasses
- 1" flat aluminum stock
- 10' 2x8 treated lumber
- 12' 4x4 treated lumber
- 3" casters
- 6' of 4" PVC pipe
- 8' 2x4 treated lumber (3)
- Exterior screws
- Nuts and bolts (stainless steel)
- Rivets (aluminum)
Finding and customizing the composter tumbler drum
You can buy drum composter tumblers online or at any garden center for as little as $150 for the smallest units and up to $400 for the large fancy rigs. They all follow the same basic design—a drum on a stand. Our version of a compost barrel is an adaptation of that using a plastic 55-gallon drum. The compost tumbler drum and stand together cost about the same as the low-price models, but our composter is built stronger and has more features. It takes a full day to customize the drum and build the stand. We used rivets to speed up the compost bin tumbler assembly, but screws, nuts and lock washers work too.
Ask for free, used 55-gallon polyethylene drums at car washes and food processing and industrial manufacturers. Since beggars can’t be choosers, you’ll probably wind up with a white, green or blue drum. If that doesn’t fit your backyard color scheme (paint doesn’t stick well to polyethylene), contact a container firm and order the color you want. We ordered a black ‘tight-head’ drum (top permanently sealed to the drum) for $52 from a local supplier.
How a compost barrel works
Waste becomes compost thanks to millions of hungry microbes, which break it down and convert it to nutrient-rich fertilizer. Those microbes need oxygen to thrive, and turning the drum daily creates fresh air pockets in the mix. You can accomplish the same thing by churning a pile of compost with a shovel, but a drum composter makes it easier. And the more thorough mixing speeds decomposition.
Rotate the Compost Tumbler Daily: Screw the bung caps into the holes to prevent compost from leaking out. Then grab the handles and rotate the drum several times in either direction to stir the mixture. Drop, Roll and Dump: Park your wheelbarrow under the drum and open the door. As you roll the drum downward, the compost will dump right into the wheelbarrow.
Project step-by-step (4)
Reinforce the compost tumbler door opening
Clamp aluminum strips in place so 1/2 in. extends into the door opening. Fasten the strips with rivets or nuts and screws. Next, use a jigsaw to cut a door panel slightly smaller than the width of your wheelbarrow. The next step takes the most time and isn’t mandatory, but it adds strength and stability to the entire door assembly: Bend 1/8-in. x 1-in. flat aluminum stock around the drum to form side reinforcements for the door opening. Cut the bent aluminum slightly longer than the door opening and mount it to the drum. Then cut flat aluminum pieces for the top and bottom of the door opening and the hinge side of the door. Mount the top and bottom door opening reinforcements in the same manner. Mount the hinges at the bottom of the door opening so the door hangs down when you empty the drum. Finish the door by adding the latches (Figure A).
Install the rotating composter paddle
Taper the ends of the paddle to match the tapered ends of the drum. Sand the paddle with a belt sander until it fits. Then install the paddle with screws. To make stirring paddles, cut an 8-ft. piece of 4-in. PVC pipe in half lengthwise using a jigsaw. Cut the halves to length so they're slightly shorter than the inside height of the drum. Arrange two halves back-to-back. Then drill and screw the pieces together to form one paddle unit. The back-to-back design is stronger than a single ‘scoop’ and allows you to rotate the drum in either direction. Repeat for the second paddle unit. Since the drum has a taper at the top and bottom, you’ll have to sand the ends of the paddles to match. Mount the paddle units 180 degrees apart and secure them to the drum with screws, nuts and washers. Finally, mount grab handles around the drum to rotate it. A tight-head drum comes with two threaded 'bungholes.' Remove the threaded caps to provide ventilation. You may need to drill additional ventilation holes if the mixture stays too wet.
Assemble the stand
Screw the legs to the rails. Then install the cross braces. Strengthen with diagonal struts. Cut the legs and deck boards to length according to the Cutting List. Then assemble the stand using a drill and exterior screws.
Mount the casters
Then set a level on top of the compost tumbler drum and pry the drum up with a board. When the drum is level, position the last caster, mark its location and screw it into place. Add diagonal struts to prevent front-to-back and side-to-side movement when spinning the drum. Flip the stand upright and mount two casters so they ride in the recess around the drumhead. Then level the drum and mount the remaining two casters.
Load, spin and dump
Load the compost tumbler drum with yard waste and add a compost starter to get the batch cooking (about $10 at any home or garden center). Rotate at least once every day to mix and aerate the batch. When the compost is ready, just dump it out.