Fractionation of Pinus radiata wood by combination of steam explosion and organosolv delignification

This work proposes a sequential combination of steam explosion and organosolv delignification for Pinus radiata fractionation.An efficient pretreatment to fully optimize the use of lignocellulosic materials is the key to make a biorefinery profitable, especially for softwoods, known to be more recalcitrant than other lignocellulosic raw materials.Steam explosion has a dual effect on biomass as morphological and chemical changes are introduced.A delignifying stage has been stated to be necessary in order to ease hydrolytic enzymes accessibility to cellulose while avoiding non-productive bonds with the lignin present.Three steam explosion conditions were tested (170°C, 5 min; 180°C, 10 min; 170°C, 5+5 min) followed by an organosolv delignification stage, carried out at two different conditions (170°C, 60 min; 170°C, 90 min).All treatment yields, delignification extent, and hydrolysis yields were determined to evaluate each stage.The steam explosion treatment did not produce high delignification extent.Maximum global delignification (50,4%) was achieved when combining the two-cycle steam explosion with the most severe post-treatment condition tested.Enzymatic hydrolysis of the cellulosic residue improved after organosolv delignification; however, hydrolysis yields did not exceed 35%.The chemical changes undergone by softwood lignins are presumably responsible for the low digestibility.