Trends in the production of cellulose nanofibers from non-wood sources

The rise of biomass-derived nanocellulose addresses the sustainability criteria now demanded of new materials, which have been widely overlooked in the plastics era—renewability, abundance, biodegradability, and recyclability. Cellulose nanofibers have conventionally been extracted from wood products, supported by an established forestry infrastructure, but the drive for biomass sustainability has encouraged researchers to explore non-wood sources over the past 15 years. Non-wood sources, including agricultural residues and industrial wastes, offer an attractive alternative due to their abundance, fast generation, and low starting value. Moreover, agricultural residues can improve the sustainability of cellulose nanofiber processing from multiple angles. The biochemical composition of the typical agricultural residue, which is lower in lignin and higher in hemicellulose than wood stems, improves the fibrillation efficiency of cellulose bundles into nano-scale fibers. In addition, agricultural residues yield high biomass volume from short growth cycles with improved land utilisation, whilst offsetting environmental issues associated with their current uses. In this work, we performed a comprehensive literature evaluation of the biomass sources used to produce cellulose nanofibers. Of the 3358 cellulose nanofiber publications from 2004 to 2018 with an identifiable source material, 57% were derived from wood-based biomass and 30% from non-wood biomass, with 100 unique biomass sources identified. Furthermore, the top research fields associated with non-wood publications included general characterisation (36%), plastic nanocomposites (19%), bionanocomposites (9%), biomedical products (8%), and electronic devices (6%). As social, political and economic drivers reinforce sustainability as a key focus in nanocellulose production, this bibliometric resource provides a timely snapshot of the sustainability trends in cellulose nanofiber research.