My neighbors Dan & Lise have three large compost bins that Dan built outside their backyard garden fence. This spring they ordered a load of leaves from the City of Eugene and then hauled cow and chicken manure to fill the bins.

Their first round of composting went fine, but after participating in the Hot Compost project at the Alton-Baker Community Garden (see slideshow link on the Garden Page), Dan thought he could improve his system.

Dan bought 4" PVC pipe and made a tall vent stack behind his bins, the vent attaches to a manifold across the upper back of the interior of the bins. Each of the three bins has a perforated pipe angling down at about 45 degrees towards the bottom front. All three of these pipes are attached to a pipe running parallel to the front of the bins at the bottom. See the photos.

Today, June 11, Dan mixed one part mostly composted leaves & manure, with one part, coffee grounds, and one part chicken manure. We think he's going to get quite a spike in temperatures with that mix and the passive aeration system. I'll report back.

But how does this passive aeration work? The microbes in the mix will begin to metabolize the material. That create heat. The heat will find its way into the pipe through the perforations. Heat rises, and Dan's tall vent stack will create a strong upward draft. As heat leaves the vent at the top, air must be replaced in the pile. So, air (with oxygen in it) will be pulled into the pile.

Great project & likely to be on the Amazon Bike Tour that's coming up this summer.