An increase of renewable biomass resources in the world fuel and energy balance contributes to reducing the harmful impact of energetics on the environment. Low efficiency of biomass (in its natural form) processing for the energetics purposes by traditional combustion methods leads to the necessity of its preliminary conversion into energy-valuable products. The purpose of this work is an experimental study of low-temperature processing of biomass with varying composition. Physical experiment and differential-thermal analysis were used as the main methods of research. Based on the systematization of the obtained data and other investigations, the dependences of low-temperature pyrolysis products yield for solid organic raw materials on the hydrogen to carbon atomic ratio have been established. With increasing of H/C ratio, the yield of the carbonaceous residue decreases whereas the yield of liquid products and gas increases. It has been established that biomass pyrolysis proceeds with the predominance of exothermic reactions providing a positive heat effect that varies from +262 to +1809 kJ/kg. At the same time, an increase of the H/C ratio in the raw materials results in an increase of the exothermic effect of pyrolysis.