Large scale torrefaction encounters difficulties in processing different types of biomass of various properties and morphologies to guarantee and maintain the required quality. Ideally, torrefaction runs auto-thermally. Key issue here is that the heat production, which is generated by combusting the produced torr-gas (gas which is released from the biomass during torrefaction), should be sufficient for the torrefaction process including losses from the system. It is essential to know the heating value of the torr-gas as a function of the torrefaction process for each biomass type (e.g. temperature and residence time). One of the problems is that this heating value cannot be determined in real-time by analyzing the gas composition because of the slow processing time of gas analysis equipment. A second drawback of gas analysis chromatography is that the tars present in the torr-gas condense and thus clog and contaminate the measurement equipment. To be able to measure this heating value in real-time, along with the development of the final product quality, a new method is proposed which to some extent resembles the actual torrefaction system in which a sample material is brought to the actual torrefaction condition while the temperature distribution in the sample is being recorded along with the generated thermal power of the ablated torr-gas.