Via YouTube channel MyLittleHomestead.com comes this video about building a rocket mass heater – a heating system that maximizes wood fuel by embedding that energy into a high mass structure, in this case, a cob bench. The exhaust is much cleaner than with conventional stoves, and one brief fire can heat a space for hours, even for longer than a full day.
And here is this review and update video made three years later:
The big secret to such complete combustion is the fire brick in the fire box. This brick reflects the heat of combustion back upon the fuel, causing it to burn much more completely than in fireplaces and other stoves. Heat in the riser pipe draws air horizontally through the fire box, making the fire burn sideways. No smoke at all comes up through the hole where you feed in the wood.