A long time ago I took an alternative energy sources course (early 1980's), and I have pulled this tidbit from my memory. Manure Pit hot water heater:
Hook up to the hot water baseboard heating in your dome, and you get water temps from 120 - 140 degrees F. sufficient to heat a small home. One can also hook up a secondary heater in the original design to heat water for bathing. As convection circulation requires a closed system, a circulating pump would probably be needed to produce pressurized hot water for showers, cooking, etc.
Offered by Ron.