A Compost Heated Greenhouse
I wrote an article about an experimental greenhouse project undertaken by the New Alchemists in the 1970s, that attempted to use the heat generated from about 25 cubic yards of composting material to heat a greenhouse through a Vermont winter.
Basically, blower fans were mounted at the top of greenhouse, that connected through ducts to the bottoms of the compost chambers, aerating the compost materials from below.
Secondary fans located above the compost chambers drew heat and exhaust gases from the compost, and expelled it into a layer of mature compost and seedbed soil, which allowed carbon dioxide to circulate up into the air within the greenhouse, but kept ammonia gases trapped within the soil layer, increasing the nitrogen content of this 'bio-filter' base layer of the greenhouse.
Even with some insufficient carpentry in the greenhouse shell, they managed to avoid freezing over the '84-85 winter in Vermont, the lettuce and parsley crops coming through unscathed.
The experiment was written up in a journal entry, and apparently abandoned, but the details of this experiment have been expanded into a mature system, by the Agrilab Technologies company, that allows agricultural operations to harvest a substantial amount of heat and energy from compostable materials, manure, farm wastes, etc.
Anyways, if it's of interest to you, let me know what you think. Thanks!