The biothermal compost heater is an attempt to utilize wood chips, an urban waste product, to produce heat for warming our greenhouse this winter. It was built at this October’s RUST class, and took 20 people approximately three hours to complete.
The heater consists of a pile of oak wood chips ten feet in diameter by six feet high, contained by two pieces of livestock panel fencing. While it was constructed, lengths of one inch polyethylene tubing were run in layered spirals throughout the pile.
The pile was continuously watered at the layers of wood chips were added.
As the wood chips in the pile decompose, they produce a significant amount of heat (already its making temperatures above 130 degrees F). Water that is circulated through the tubing by a pump will run in to the greenhouse, where it will run through heat exchangers in the fish ponds. We are hoping the biothermal heater will help us to reduce or eliminate our dependency on propane heat this Winter, and result in a pile of composted wood chips this Spring.
The Radix Ecological Sustainability Center 
Looks great! I’ll be interested in seeing the results over the winter.
BTW – “Grow Power” in Milwaukee just puts a compost pile in each of their hoop houses. It requires the extra few square feet of space, but reduces the technical complexity a bit (water pipes, heat exchangers, etc). I will be good to compare the two approaches.
Awesome! Hope it works out well 🙂