Isolation of Lignin

Lignin is produced by the cell walls of plants, agricultural crops, and wood. Between 15 and 40% of the dry matter in woody plants is made up of lignin, which is mainly a structural material that gives cell walls more strength and rigidity. Compared to cellulose and other structural polysaccharides, lignin is more resistant to the majority of biological attacks. Currently, chemical pulping of wood yields lignin. However, a number of biomass refineries are now operational. P-coumaryl, coniferyl, and sinapyl alcohols are the three basic phenylpropane units that make up lignin's chemical structure. The pulping process produces the technical lignins as a byproduct. The most commonly used commercial lignins are kraft lignin and lignosulfonates. Organosolv lignins are another type of lignin. Isolation and characterization of different types of lignin are presented in this chapter.