An experimental comparison of lignin yield from the Klason and Willstatter extraction methods

This work compares the performance of two lignin extraction methods applied to several crops grown in Brazil and contributes to identify the biomass with more potential for generation of thermal energy from the point of view of its lignin content and properties. A full factorial (22) design involving two particle size distribution (105 to 500 μm and 1000 to 2000 μm) and two extraction methods (Klason and Wilstatter) were chosen as controlled factors for the tests, including the determination of granulometry, extractives and holocelluloses, higher heating values, and the proximate and ultimate analysis. Results showed that lignins obtained utilizing both methods have elevated higher heating values, suggesting they could generate thermal energy from thermochemical processes, mainly those lignins extracted from the Klason method. Even though the tendency for obtaining more lignin yield by using the Klason extraction method and fine particles was observed for almost all raw material tested, the statistical analysis suggested that for the experimental range studied the extraction method and the particle size distribution do not affect the lignin yields at 95% of confidence level (p-value < 0.05), except the lignin yield obtained from sugarcane bagasse. For this biomass, the extraction method chosen led to relevant differences in the lignin yield (22.6% by using Willstatter to 24.9% by using Klason), suggesting that the lower pH level used by the Klason method promotes a more efficient lignin extraction.