Thermal analysis of thermally treated spruce wood after its accelerated aging

In contrast with untreated wood, thermally treated wood has a much longer lifespan, and compared to chemically modified products, its valorization after the end of the life cycle is much easier. We investigated the effect of thermal modification of spruce wood at temperatures of 160, 180, and 210 degrees C, the industrial product Thermo-D, and the effect of accelerated aging (600 h in Xenotest chamber, wet mode) on its energy properties. We used calorimetry, elemental analysis (CHNO), thermal analysis-thermogravimetry (TG, DTG), and differential scanning calorimetry (DSC). The results of calorimetry show that the higher heating values (HHV) increased significantly because of the thermal modification temperature. We noticed a similar trend after accelerated aging (HHV = 20,061-21,515 (kJ kg-1)). Relations between experimentally determined HHV values and values calculated from chemical composition and elemental composition show a very good mutual correlation (r = 0.8876-0.9710). Thermal analysis shows a higher content of thermal energy in modified and aged wood in comparison with untreated sample. The obtained knowledge can be applied for the energy use of Thermowood at the end of its life cycle, depending on the conditions of its treatment, and it can also be used for fire risk assessment of Thermowood products.