There’s an interesting group called All Power Labs who research biomass gasifiers: in lay terms they make machines that can convert hay, wood chips, nutshells (a large variety of biomass substances) into clean gas products which can be used to power other things – such as a diesel engine generator (which they do). You can see this system at work here:
They got my attention because if/when we go off-the-grid we will likely need a backup source of energy in winter months – the simplest being a diesel generator. But that requires diesel. So the potential of a generator that can run on biomass of which we have plenty is pretty exciting and fills another gap in the sustainability puzzel.
Their CEO Jim Mason appears in a series of 3 videos (~2.5 hours) which finally provided me with an explanation on how burning works. I admit that parts of it were a bit beyond me but for the most part I was able to follow it and learn what actually happens when I burn wood for heat (namely 4 processes: drying, pyrolysis, gasification, combustion).
It refined my understanding and appreciation of what goes on inside Rocket Stoves. Most stoves or fireplaces are only able to burn ~20% of the potential energy in wood, most of the rest is released as gasses which for the most part escapes out the chimney unburned. A lose-lose situation: losing potential energy and releasing pollutans into the atmosphere. A typical rocket stoves will burn most (if not all) of those gasses – already making it 4 to 5 times more efficient then most wood burning stoves. Then, after a clean and efficient burn the heat that is generated is retained in a thermal mass … which easily brings them to 10 times better.