These ingenious cook stoves, invented by Professor Ravikumar, work on the principle of having a combustion chamber inside a retort. An outer chamber (the retort) is filled with biomass for turning to biochar. An inner chamber (the combustion chamber) is then filled with biomass (sticks) which is lit from the top. The heat in the combustion chamber passes through to the retort initiating pyrolisis of the biomass in the retort. The wood gases pass through holes into the bottom of the combustion chambar, where they combust.