Valorization of heat-treated wood after service life through a cascading process for the production of lignocellulosic derivatives

Abstract

The present work proposes a cascading approach to fractionate thermally treated wood after life service and untreated wood and their unweathered counterparts. The fractioning of wood was implemented, focusing on the current trends in environmentally friendly processing and processes with a noteworthy yield and purity. Resulting streams: cellulose, hemicelluloses, and lignin. These fractions were analyzed utilizing spectroscopies (ultraviolet and infrared), chromatography (liquid and gas), thermogravimetry, and x-ray diffraction (thermal treatment and weathering). Results showed no significant difference in yielding or the quality of the extracted celluloses (only a slight increment of the crystallinity after the thermal treatment). Considering the hemicellulose fraction, it was observed a considerable mannose reduction after the thermal treatment (≈37%) and weathering (≈27%), or the combination of both (≈51%). Nevertheless, the most notable changes were observed in the yield and the quality of the obtained lignins with higher yields for untreated wood (Po) and more purity (>93%) for lignin samples obtained during the delignification process (L1). Their structure was also affected by the fraction from which they were extracted, as reflected by the S/G ratio. Moreover, the thermal and weathering treatment improved their thermal properties, as shown by thermogravimetric analysis. In general, the present work proved the feasibility of valorizing thermally treated wood after service life within a biorefinery system to obtain competitive value-added products to optimize resources and extend the utility time of such biomass.