Wood waste valorization: Ethanol based organosolv as a promising recycling process

Wood waste is a valuable material that could constitute an abundant and inexpensive source for the production of new materials the recovery of energy. In Europe, about 46% of wood waste is recycled to particleboard and fiberboard, while the other fraction is incinerated. However, a considerable quantity of wood waste shows potential for its transformation into value-added products due to its compositional quality. In this work, wood waste collected at a mechanical treatment plant underwent organosolv treatment to produce a cellulose pulp suitable for manufacturing containerboard. Three variables (temperature, acid concentration, and ethanol concentration) were investigated to find an optimal solution to produce wood pulp by means of Design of Experiment. Wood waste was microwave-heated at 160 °C for 15 min using an acidified ethanol-water solution (2% w/w H₂SO₄ and 0.8 w/w ethanol concentration), producing pulp with an average cellulose content of 76% where 93% of initial cellulose was retained. Thanks to a one-pot approach, ethanol was totally recovered, 62% of initial lignin was precipitated, and 20 g/l of hemicellulose-derived sugars solution was obtained. Finally, three wood waste samples collected in different periods of the year yielded comparable outcomes, suggesting a good reproducibility of the organosolv process. ANOVA test with a significance level of 0.01 showed a p-value of 0.029 and 0.235 for cellulose content and cellulose recovery, respectively. This study paves the way for an industrial symbiosis between recycling centers and paper mills located in the same territory.