Optimization of Deep Eutectic Solvent Pretreatment of Oil Palm Empty Fruit Bunch Incorporated Assistive Heating Methods

One of the most underutilized biomasses wastes in Malaysia is oil palm empty fruit bunch (EFB). Lignin presented in EFB was found to contain the highest energy content compared to hemicellulose and cellulose. Therefore, EFB can be the sources of lignin extraction to generate profit for the oil palm industry. Deep eutectic solvent (DES) has emerged as a new green solvent in biomass fractionation field as it has impressive delignification efficiency and low toxicity. Many researchers had delignified biomass using DES with conventional oil bath heating. The conventional method for delignification is energy-intensive and involving long pre-treatment time. Hence, this study aims to achieve effective extraction yield while reducing energy usage to extract lignin from oil palm empty fruit bunch (EFB) using DES with aid of microwave heating (MAE) and ultrasonic irradiation (UAE). The feasible extraction scheme was used to investigate parameters include water content in DES, irradiation duration, and heating method power. The crucial parameters affecting MAE pre-treatment was found to be microwave power and duration. As for UAE pre-treatment, ultrasonic amplitude and water content in DES plays a significant role on delignifying EFB using DES. In addition, the models developed for both pre-treatments are identified to be significant and thus the optimized pre-treatment conditions can be obtained. This finding is anticipated to generate an effective DES pre-treatment with integration of assistive heating techniques. From regression analysis, the optimized condition for UAE pre-treatment is at 75% amplitude for 8 min 38s, resulting in an 13.20% of lignin removal from EFB. As for the MAE pre-treatment, 56.30% of delignification efficiency was achieved using optimized condition at 300 W for 2 min 42 sec.