Hydrothermal pretreatment of biomass‑waste‑garlic skins in the cellulose nanofiber production process

This study investigated the effects of hydrothermal pretreatment, depressurization (DP) cycles and temperatures, of biomass-waste-garlic skins on cellulose nanofiber (CNF) production processes and CNF properties. SEM, TGA, FTIR and chemical analysis approved the difference in the compositions of fibers obtained under various conditions. High temperature and high DP cycles enhanced defibrillation and produced fibers with high cellulose composition, which subsequently affected bleaching time, yield, thermal stability, and crystallinity of CNFs. However, a large amount of pseudo-lignin was observed at 150 °C and 170 °C leading to longer lignification and lower yields. The optimum condition for hydrothermal pretreatment at 130  °C and 5 DP cycles could eventuate much uniform CNFs with the largest aspect ratio, high crystallinity, and thermal stability.