Compost tumbler

The residue from the larvae needs to mature. Originally it was my goal to shift it straight to the worms to finish, but the vermicomposting process doesn't heat sufficiently to kill pathogens. They also take a little longer. My intent is to go from food refuse to soil amendment as efficiently as possible. 

To compost correctly in a pile, it needs to be at least three cubic feet. A compost tumbler will work with a smaller amount of material. I didn't have a sufficient amount of material to work with in a pile so a compost tumbler was added to my wish list.

The barrel came from Surplus City: 55 gallon without a lid. We had to bolt on the lid (the white end seen in the photos). The lumber used in the frame was originally deck boards from a deck demo. The lumber used for bracing and the handle was from an old couch. The PVC pipe axis that the barrel spins on came from someone's garage. The reinforcing axis supports that the PVC pipe runs through are composite material leftover pieces from the new deck. The bolts were salvaged from various other projects.

This is the loading side for raw materials

This is the side where a wheelbarrow can fit comfortably and the finished contents and be emptied

  

Here you can see the composite material support piece as well as one of the fancy lap joints
we made to create a very stable frame

Interior view of the spinning axis

The residue has been composting for a couple weeks. I added some grass clippings to speed up the composting. It smells like dirt at this point, which means it's ready for application

Working inside the barrel to tighten the bolts

Helper dog is a big help

Some hardware was brand new: the latches that secure the hatch, metal for the interior stirring paddles, hinges, handles for turning, wheels and the axles for the wheels. Having it on wheels, though a bit cumbersome, still makes it much easier to move than if it had no wheels. 

More details of the build: The ventilation holes are 5/8 inch. We went with lap joints for the main supports because they are extremely strong. It's a little more effort but requires less hardware and the end result leaves no question of strength. We tried our best to get the latches on the hatch to be snug but the plastic flexes in the heat. An old coat hanger wire makes sure that they stay closed since the latches have loosened over time. It works.