Extraction of Lignin from Various Agricultural Biomass: Its Characterization and Applications

With the continuous transformation of social consumption demand to the direction of green and sustainable development, the demand of humans for green and renewable resources is increasing. Lignin, as a naturally synthesized polymer, is widely found in plant cell walls. It has high carbon content and energy storage, which is renewable. If used reasonably, it is expected to become one of the most available renewable biological resources. At present, although there is a large amount of lignin in agricultural wastes, its extraction and valid utilization are limited due to its structural complexity and heterogeneity. Therefore, it is of great significance to effectively and rationally utilize and realize the high-value conversion of lignin. To further study how to efficiently extract lignin from agricultural biomass and its characterization and application, the pretreatment methods of agricultural waste for lignin extraction are introduced at the beginning of this chapter, including physical, chemical, and biological treatments. Then, the traditional methods of lignin extraction from different agricultural biomass (such as high-boiling alcohol solvent extraction and organic solvent extraction) are described. Thirdly, some typical characterization techniques of lignin are introduced, including nuclear magnetic resonance (NMR) and two-dimensional nuclear magnetic resonance (HSQC NMR) methods. In terms of application, lignin has been applied to different fields due to its good dispersion, adhesion, and surface activity, such as industrial, agricultural, and medical fields. Besides, lignin is also used as a binder, dispersant, and surfactant. In general, lignin, as a natural renewable polymer, has a high possibility of industrial production due to its abundant resources and low price. In the pursuit of green environmental protection and sustainable development today, it has become a key research hotspot.