This old-world heating technology is extremely efficient without needing to use new-world technology. The gist is to take a large thermal mass (e.g., limestone blocks) and burn fuel at a very high temperature in a short time to get complete combustion (CO2, trace mineral ash, and trace incomplete combustion products). The thermal mass stays at a temperature that's warm to the touch and radiantly releases the heat over an entire day.
Radiant heat does not dry the air nor does it cause problems with dust circulation as does convection heat (furnaces). A properly designed masonry heater can heat a 2000 sq. ft. area for an entire day at comfortable temperatures with only six pounds of dry wood. These heaters produce very little soot and are significantly safer than pellet or wood stoves. With simple maintenance, these heaters can last for generations.
My own interest is partly in their sheer simplicity. The materials and tools are easy to acquire, and the construction should be straightforward with minimal masonry experience. My other interests are in using it effectively as a valued part of my non-waste home. I've been considering using the heater's CO2 output as input to algae tanks or a greenhouse. I'm also excited by the prospect of using excess glycerine from biodiesel production as a fuel input for the heater too.