Energy and property trade-offs in nanocellulose production: High-pressure homogenization at different processing consistencies

Abstract

Cellulose nanofibers are gaining attention as innovative biobased materials due to their remarkable surface area, versatility in functionalization, and superior mechanical properties, making them ideal for applications in papermaking, material engineering, and wastewater treatment. However, their production via fibrillation is both energy-intensive and expensive, creating barriers to large-scale adoption. This study explores how processing consistency influences energy and cost efficiency during the high-pressure homogenization of TEMPO-oxidized bleached eucalyptus kraft pulp. Results reveal that energy consumption initially depends on processing volume but later becomes constrained by viscosity. The optimal homogenization condition was not at the highest fiber content, where energy demand would be expected to be at its lowest, but at an intermediate consistency where viscosity allowed efficient equipment operation. Increasing processing consistency was observed to improve fibrillation efficiency and facilitate the transition from micro- to nanoscale structures by promoting shearing both between the fibers themselves and between the fibers and the equipment. Furthermore, the processing concentration significantly impacted the final nanofiber characteristics, particularly viscosity as a 0.5 wt% suspension, due to variations in fiber morphologies and network structures such as aspect ratios, entanglement, and bundles. A techno-economic analysis showed that while higher energy usage is required for some conditions, transportation cost savings can offset these expenditures, making intermediate consistencies the most economical choice depending on transport distances. Ultimately, this study emphasizes the importance of balancing cost efficiency and nanofiber quality to optimize production for diverse industrial applications

The authors acknowledge the financial support of the Spanish Ministry of Science, Innovation and Universities to the project ArtInNano (CNS2022-135789) and thank the NanoBio-ICMG Platform (UAR 2607, Grenoble) for granting access to the electron microscopy facility. Giovana Signori-Iamin received funding for her PhD thesis from the University of Girona (PhD grant IFUdG2023). Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

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