The heating value of volatiles released from a solid fuel particle during pyrolysis is determined as a function of time. The experimental setup consists of a thermogravimetric analyser (TGA) and a flow-calorimeter (FC). One single fuel particle is quickly inserted into the TGA which is continuously purged with N-2 and operated at a constant temperature of 825 degreesC. The evolved volatiles are burnt in the FC with air while maintaining an excess of oxygen. The temperature change of the FC corresponds to the heat production rate (HPR) from combustion of the volatiles. The relation between temperature change and HPR is given by the convolution integral. The Hammerstein approach describes the non-linear response behaviour of the FC. The heating value of the volatiles is calculated from the HPR and the mass loss of the particle. The experimental setup was calibrated with C3H8 and applied to gas from the pyrolysis of a single dry beech wood cube (15 mm x 15 mm x 15 mm). It was found that the heating value of the released volatiles shows two maxima during the pyrolysis process.