Strategizing Assistive Heating Techniques on Delignification of Empty Fruit Bunch with Incorporation of Deep Eutectic Solvent

A biomass pretreatment utilizing biodegradable deep eutectic solvent (DES) incorporated into assistive heating techniques, would lead to an energy-efficient extraction. To achieve effective extraction yield while reducing the energy usage, lignin in oil palm empty fruit bunch (EFB) was extracted using DES with microwave heating and ultrasonic irradiation in the current study. The feasibility of lignin extraction using the heating methods in sequential order was examined ensued by optimization study with investigated parameters include water content in DES, irradiation duration, and heating method power. The best sequential ultrasonic irradiation-microwave heating (UMAE) resulted in delignification efficiency of 82.7% within 1 h. The yield is comparable with that using oil bath heating and same DES, but the latter involved 8 folds longer extraction time. The lignin obtained from this method is thermally stable (similar to 356 degrees C decomposition temperature), with significant amount of phenolic compound and beta-O-4 bonds (> 80%), implying that it has the potential for downstream modification. The mechanisms of delignification using DES-incorporated assistive heating methods were discussed. This study demonstrated that combining DES and UMAE in lignin extraction is simple and efficient, resulting in an 40% energy reduction and 90% decrease in pretreatment duration as compared to conventional method.

Automated summary

This study demonstrates the use of biodegradable deep eutectic solvent (DES) combined with assistive heating techniques for biomass pretreatment, resulting in an energy-efficient extraction. Sequential ultrasonic irradiation-microwave heating (UMAE) is found to be the most effective method for lignin extraction, achieving a delignification efficiency of 82.7% within 1 hour. The DES-incorporated UMAE method offers a 40% reduction in energy consumption and a 90% decrease in pretreatment duration compared to conventional methods.