Elemental composition of wood as a potential marker to evaluate heat treatment intensity

Microanalyses of pine and beech blocks treated under nitrogen at 240 °C for different times have been investigated to evaluate correlation between mass loss due to treatment and elemental composition. Oxygen content decreases with treatment intensity and is directly proportional to treatment time. In the same time, carbon content increases significantly indicating formation of carbonaceous materials within the wood structure. Acetylation has been investigated to evaluate the effect of heat treatment on the quantity of free hydroxyl groups present in the wood. The results indicate a significant decrease of reactivity of heat-treated samples compared to untreated ones. Although this decrease depends on the treatment intensity, no obvious correlation was observed between weight gain due to acetylation and mass loss due to treatment. All these results suggest that elemental composition of heat-treated wood could be a valuable marker to evaluate mass losses due to thermal degradation and consequently treatment intensity.