Toward waste valorization by converting bioethanol production residues into nanoparticles and nanocomposite films

Guillaume N Rivière,Florian Pion,Muhammad Farooq,Mika H Sipponen,Hanna Koivula,Thangavelu Jayabalan,Pascal Pandard,Guy Marlair,Xun Liao,Stéphanie Baumberger,Monika Österberg

doi:10.1016/j.susmat.2021.e00269

Abstract

A “waste-valorization” approach was developed to transform recalcitrant hydrolysis lignin (HL) from second-generation bioethanol production into multifunctional bio-based products. The hydrolysis lignin (HL) was extracted with aqueous acetone, yielding two fractions enriched in lignin and cellulose, respectively. The soluble hydrolysis lignin (SHL) was converted into anionic and cationic colloidal lignin particles (CLPs and c-CLPs). The insoluble cellulose-rich fraction was transformed into lignocellulosic nanofibrils that were further combined with CLPs or c-CLPs to obtain nanocomposite films with tailored mechanical properties, oxygen permeability and antioxidant properties. To enable prospective applications of lignin in nanocomposite films and beyond, CLPs and c-CLPs were also produced from a soda lignin (SL) and the influence of the lignin type on the particle size and ecotoxicity was evaluated. Finally, the carbon footprint of the entire process from hydrolysis lignin to films was assessed and an integration to industrial scale was considered to reduce the energy consumption. While most previous work utilizes purified lignin and pristine and often purified cellulose fibers to produce nanomaterials, this work provides a proof of concept for utilizing the recalcitrant lignin-rich side stream of the bioethanol process as raw material for functional nanomaterials and renewable composites.

Highlights

Expansive utilization of fossil-based resources for fuels and packaging has a detrimental impact on land and marine ecosystems [1,2,3,4] and contributes to the acceleration of global warming [5,6]
This section reports on the fractionation process and the characteristics of colloidal lignins particles (CLPs) recovered from the hydrolysis lignin (HL) and the soda lignin (SL) used for comparison, it focuses on the preparation of the nanocomposite films by assembling the HL fractions into a CNF-based nanocomposite
SL was rich in lignin (89.1 wt% according to the Klason method) and contained only 1.85 wt% of carbohydrates, consisting of hemicelluloses mainly composed of arabinose and xylose

Summary

Introduction

Expansive utilization of fossil-based resources for fuels and packaging has a detrimental impact on land and marine ecosystems [1,2,3,4] and contributes to the acceleration of global warming [5,6]. Several bioethanol production processes using lignocellulosic biomass as a feedstock have been developed in the past few years [11]. These processes are mostly based on acid-catalyzed steam explosion and enzymatic hydrolysis, and generate a recalcitrant solid residue termed “hydrolysis lignin” that contains unhydrolyzed residual carbohydrates in addition to lignin phenolic compounds and some minor components [12]. Though burning part of this by-product that represents more than 40% of the initial lignocellulosic feedstock is necessary to reduce fossil fuel consumption and ensure energetic autonomy of the process, its valorization into functional bioproducts would increase the overall sustainability of the process. One of the main obstacles to the valorization of this lignin-rich residue lies in its chemical heterogeneity, which hinders its direct applicability without further treatment or fractionation [13]

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Conclusion