Enhancement of cellulose nanocrystal yield from oil palm empty fruit bunches: A comparative study of binary and ternary deep eutectic solvents with pulsed electric field pretreatment

Effective pretreatment of lignocellulosic biomass is essential in ensuring sustainable cellulose nanocrystal (CNC) production. Binary and ternary deep eutectic solvent (DES)-based pretreatment coupled with assistive techniques has yielded high cellulose extract and lignin removal efficiency. In addition, pulsed electric field (PEF)-assisted pretreatment showed good performance to accelerate the lignocellulose fractionation process under mild conditions. However, the production of CNC from oil palm empty fruit bunches (OPEFBs) by utilizing binary and ternary DES incorporated with a PEF requires in-depth exploration to provide insights into its electroporation effect based on different DES properties. This study investigates CNC production from OPEFB pretreated with binary and ternary DES integrated with PEF. The extracted cellulose (EC) and CNC were evaluated for their characteristics and energy consumption. Simulations of binary and ternary DES properties assessed current and voltage distribution in the PEF chamber. Under 6 kV/cm for 3 min, the pretreatment achieved high solid recovery, alpha-cellulose, lignin removal, and EC crystallinity. CNC has yield ranged from 78.44 to 83.62 %, with dimensions of 120.5-126.9 nm of length and 10.2-10.4 nm of width, and a crystallinity index of 81.3-83.7 %. The DES-PEF method demonstrated faster processing (3 min) and lower energy consumption (0.4-2.1 kWh/kg) compared to DES-conventional heating, with total of CNC production energy at 36-38 kWh/kg. Overall, the binary DES demonstrates better OPEFB pretreatment efficiency than the ternary DES when incorporated with the PEF-assistive technique. This novel and innovative method devises a time- and energy-saving biomass pretreatment for sustainable CNC production.