The article presented the processes of pyrolysis and gasification of biomass leading to the preparation of liquid hydrocarbon fractions in the synthesis of Fischer-Tropsch and processes HTU. Preliminary thermogravimetric testing of biomass samples was conducted on the STA 449 F3 Jupiter® coupled with the gases analyzer - spectrometer QMS 403 Aëolos. These studies were carried out for samples of cereal straw, crushed to a state of dry dust. The temperature regime provided that the samples were heated to the temperature of 750°C at the heating rate of 10 K/min. Gases (nitrogen, argon or carbon dioxide) were used with flow rates of 60 ml/min. The results, along with discussion, are presented in graphs - TG curves and mass spectrum.