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

Camila María Imlauer-Vedoya,María Cristina Area,Priscila Vergara-Alarcón,Esteban Revilla,Juan Carlos Villar,Fernando Esteban Felissia

doi:10.4067/s0718-221x2019005000414

Abstract

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 chemicalchanges 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 treatmentyields, 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, hydrolysisyields did not exceed 35%. The chemical changes undergone by softwood lignins are presumably responsible for the low digestibility.

Highlights

The environmental degradation due to greenhouse gas emissions, the increasing energy demand and the progressive depletion of fossils fuels have strengthened the interest in alternative, renewable resources to meet society basic needs of products and services (Alvira et al 2010)
The solid fraction obtained as a result of the steam explosion pretreatment consisted mainly of cellulose and lignin
There is an increase in the delignification extent as the SE severity increases, up to a point where condensation reactions prevail. Both physical and chemical changes of the lignin present in the steam exploded material would have a direct impact on downstream processes, but the influence of the SE severity on delignification depends on the type of post-treatment (Kumar et al 2011)

Summary

Introduction

The environmental degradation due to greenhouse gas emissions, the increasing energy demand and the progressive depletion of fossils fuels have strengthened the interest in alternative, renewable resources to meet society basic needs of products and services (Alvira et al 2010). The chemical composition of the P. radiata chips and the solid fractions obtained after the steam explosion and the organosolv delignification were determined by following the NREL/TP-510-42618 standards.

Results

Conclusion