The "guy in France" referred to several times was likely Jean Paine.
He coiled black plastic pipe around a tank, buried deep in a pile containing 200 tons,+, of material. He pumped water through the tubing to heat the house and provide hot water.
The tank contained similar material to what the pile consisted of and was used as the methane generator.... the tank being "cooled" by the water circulating through the pipes to maintain around 95-105 degrees, F.
A typical pile will heat to 150-155 degrees, F. More than that is a little too hot and some nutrient can be lost. A pile containing 200 tons, give or take, according to Jean Paine, would heat effectively for 18 months.
What I have done is:
Building a durable compost bin.
I built the thing in October(ish) 2005.
I filled all three bays with pretty good stuff and it was
cookin'.
Our ambient kitchen temperature has always been 60-65 during the winter.
That December, 2005, was a cold one, and the kitchen maintained 70-75 and we burned a little over half our regular amount of firewood that winter.
Now that's my cabin/house.
The difference anywhere else would depend on a few things, but, if one were to design a house with compost heat in mind.....i.e. concrete walls and some plumbing/planning, I think it could easily be a stand alone.
One would just figure on cleaning stalls and garden residuals each September/October and spreading the piles the following May/June.
On the other hand, if that pile cooled down to earth temps, it would make excellent insulation against the summer heat.
As for the pile's heating tendencies, the concrete would replace the outer insulating layer, and therefore absorb more heat than what would be realized toward the outer portion of the pile exposed to the elements.
Berm a house on the northern exposure and compost pile heat the east and west.
Give the south full, greenhouse style sun and I say you've got it licked.
