A free-standing, thermostatically controlled stove provides positive draft combustion of bio-mass pellets or cereal grains. Particulate bio-fuel is gravity fed from a hopper into a first slower moving auger conveyor which feeds a second faster moving sugar conveyor that communicates with the lower side portion of a combustion container carried in a combustion chamber. A pilot burn is continuously maintained in the combustion container end of the second conveyor. The combustion container has vertically spaced air plena that provide combustion air and input holes to allow recirculation of combustion chamber gases for secondary combustion. The fire chamber exhausts combustion gases through a negative pressure, downdraft type exhausts with a selectively openable valved orifice to allow updraft operation at critical burning periods. A programmable micro-processor regulates operating parameters to provide distinguishable pre-programmed combustion cycles for maximum efficiency with only two operator controls for off/on and thermostatically controlled operation.