5. Mild-Acidolysis Lignin: Extraction

This chapter explores the extraction and valorization of lignin, the second most abundant natural polymer and the most abundant aromatic biopolymer on Earth. It delves into the structure, molecular weight, and physicochemical properties of lignin, highlighting its importance as a supporting structural unit in plant cell walls. The text discusses various methods of lignin isolation, including kraft, lignosulfonates, soda, organosolv, and mild-acidolysis, with a focus on the latter. Mild-acidolysis lignin extraction is presented as a promising method for obtaining lignin close to its native form, suitable for further biochemical conversion. The chapter also covers the sources of lignin, such as hardwood, softwood, and agricultural residues, and their lignin content. It concludes with the potential of lignin valorization in producing high-value chemicals, biofuels, and biomaterials, emphasizing the need for improved isolation techniques to fully realize its potential in sustainable development and the circular economy.