Separation process optimisation and characterisation of lignin from black carob tree sawdust into a biorefinery

Abstract

Biorefineries are meant to play a key role as regards both the complementation of energy sources and the integral exploitation of biomass. Wood residues left over from industrialisation have a high potential to obtain numerous bio-based products. The aim of this work was to obtain high quality and high purity lignin as well as a solid product rich in carbohydrates with not more than 10%ODW of the remaining acid-insoluble lignin. To achieve this goal, a soda-ethanosolv process was optimised for the delignification of washed black carob tree sawdust (WBCTS) using a central composite experimental design; afterwards, the time of reaction was adjusted. The optimum process (19.9% NaOH (ODW of WBCTS) and 58:42 EtOH:H2O) was found, and then the reaction time was adjusted to 80 min for a higher delignification (pretreated WBCTS with less than 10%ODW). Therefore, the lignin recovered from the liquor of the SodEt process is of high quality and good purity and, the IR spectrum of the lignin is consistent with GS lignins. The results found could be used to establish sustainable chains of high value of bio-based products obtained from black carob tree sawdust and by using low-impact technologies with low environmental impact which could be applied to biorefineries.