Benchmarking the Production of Cellulose Nanofibres: Biomass Feedstock, Mechanical Processing, and Nanopaper Performance

Abstract

Lignocellulosic biomass plays a vital role in the global shift away from the utilisation of non-renewable petrochemical resources. An emerging class of biomass-derived material is nanocellulose, which are typically generated from the deconstruction of cellulose bundles within the cell wall of terrestrial and aquatic plants, either in the form of cellulose nanocrystals (CNCs) or cellulose nanofibres (CNFs). However, the utilisation of biomass has an inherent challenge associated with product variability, both in terms of the starting feedstock properties, the wide range of processing routes available to generate nanocellulose, and the fabrication of nanocellulose into a diverse range of different product formats. As a result, it is very difficult to accurately characterise and benchmark the wide variety of nanocellulose materials described within the literature. To address this challenge, this study presents a threefold benchmarking assessment of CNF material, including: (1) CNF generated from different biomass sources, including sorghum (leaf, sheath, upper stem, lower stem), banana (leaf, stem), sugarcane (mulch, bagasse), spinifex (leaf), and softwood (stem); (2) CNF generated through different mechanical processing methods, including Silverson mixing, twin screw extrusion, high energy bead milling, and high pressure homogenisation; and (3) CNF-derived nanopaper mechanical performance described within the literature and the specific energy consumption required to generate this material. The biomass benchmarking study highlighted sorghum and banana stem as the most sustainable biomass feedstock, while the mechanical process benchmarking study highlighted twin-screw extrusion as a promising low energy consumption fibrillation method. Lastly, the nanopaper benchmarking study aided in the visualisation of the nanopaper research landscape. Sample benchmarking in this manner helps to provide greater insight into the mechanisms driving nanocellulose material performance and processing sustainability.