When using the novel N-2 explosive decompression pre-treatment, its effect was investigated in relation to the biomass structure and chemical processes during the treatment process. The results that were gained from this testing were compared to those for the widely-used steam explosion pre-treatment method in order to be able to present the advantages in using each method. Both methods are economically and environmentally attractive since only the pressure and water or steam are used to break down the biomass structure. Two pre-treatment methods were used at different temperatures and samples from various process steps were analysed. The results were used to assess the pre-treatment effect and the chemical changes in the biomass and, finally, mass balances were compiled for the bioethanol process at different process steps. The results show that the highest glucose and ethanol yields were obtained by means of the steam explosion pre-treatment method at a temperature of 200 degrees C (24.29 g and 12.72 g for 100 g of biomass respectively), and at 175 degrees C (15.4 g and 9.0 g for 100 g of biomass respectively). At lower temperatures the nitrogen explosion treatment produced better yields. (C) 2019 Elsevier Ltd. All rights reserved.