Effect of Operating Parameters on Lignin Extraction from Empty Fruit Bunches and Rice Husk Using Malic Acid-Sucrose-Water Low Transition Temperature Mixture

Low transition temperature mixture (LTTM) is an attractive green solvent alternative to ionic liquids, particularly for lignin extraction from biomass, given its relatively low synthesis cost and environmental compatibility. Lignin is an unwanted by-product of thermochemical processing and is often discarded due to its recalcitrant nature. Given the potential of lignin as a feedstock for pyrolysis, it is desirable to extract lignin in the biomass. Malaysia has tremendous biomass resources from agricultural activities such as empty fruit bunches (EFB) from the palm oil industry and rice husk from the rice mills. The biomass wastes create an opportunity to harness LTTM for the extraction of lignin. However, there is still lack of insight into the operating conditions that govern the lignin extraction efficiency and lignin purity of the extraction process using malic acid-sucrose-water LTTM. This work aims to evaluate the effect of different operating parameters such as temperature, biomass to LTTM ratio, and reaction time on the lignin extraction efficiency and lignin purity. As temperature increases from 70 to 110 °C, the lignin extraction efficiency of EFB increased from 7.67 to 53.70 %, while lignin yield of rice husk increased from 3.80 to 55.74%. The lignin extraction efficiency of EFB increased from 5.57 to 56.82%, while rice husk increased from 6.46 to 38.22 % as biomass to LTTM ratio decreases from 1:10 to 1:40. The extraction efficiency of EFB and rice husk increased from 10.62 to 59.92 % and 4.64 to 20.26 % when the reaction time increased from 2 to 8 h. The highest lignin purity was obtained at 6 h with a fixed operating temperature of 100 °C, and biomass to LTTM ratio of 1:20 for EFB and rice husk were 88.32 and 85.84 %, respectively.
Proceedings of the 30th European Biomass Conference and Exhibition, 9-12 May 2022, Online, pp. 940-944