Apparatus for controlling the operation of a biomass stove utilizes three proportional integral derivative (PID) controllers as part of a closed loop to control the fuel feed rate, the convection fan speed and the combustion fan speed. The first loop controls room temperature, the second loop controls the convection fan speed and the third loop controls the combustion fan. Appropriate temperature readings are utilized for the first and second loop. The third loop, which utilized feedback of the ratio between the heat exchanger temperature to the exhaust temperature, in addition to measuring these temperatures also references a library of look-up tables of such ratios over the entire heat range of the stove that have been correlated to combustion efficiency, as an input. This enables the operator to optimize the heat output for any operating point.