At first, this was a "that's kind of interesting" idea to me, but it has become more and more of a "that might really work" sort of idea.
Basically these schemes (there are several shown) start with a carefully constructed, large pile of biomass. The biomass heats up as it goes through the composting process. Pipes running through the pile pick up heat which can be used for domestic water heating and/or space heating. Some schemes simultaneously collect bio-gas, which can be used for cooking fuel or even running a vehicle or generator.
Marc's compost furnace under construction.
A lot of work was done on this in the 70's by Jean Pain in France. The section has some good descriptions of Pain's work, including two newly added videos (thanks to Curbie for these).
Marc's compost furnace work is very interesting, and includes some results from his first winter of operation.
The MB-Soft work in this area is interesting, if a little hard to decipher.
The New Alchemy papers are also quite good.
The attraction of this approach to me is that it holds the promise of a carbon neutral way of generating useful amounts of heat over long periods of time. Some of the Pain piles are said to have been still generating useful heat after 18 months. It is quite a bit of work to build one of the structured compost piles and set up the heat extraction plumbing, but then you may be able to get useful heating from the pile for an entire heating season.
The efficiency is claimed to be of the same order as burning the biomass -- maybe even a little better. In many cases, the biomass can be material that would just be left to rot in place.
Does anyone have more useful information on this area?
Any thoughts on how useful and idea this might be?
Gary