Role of lignin in a biorefinery: separation characterization and valorization

Lignin, a major component of the cell wall of vascular plants, has long been recognized for its negative impact and treated as a by‐product in a biorefinery. This highly abundant by‐product of the biorefinery is undervalued and underdeveloped due to its complex nature. The development of value‐added products from lignin would greatly improve the economics of the biorefinery. The inherent properties of lignin significantly affect the productivity of the biorefinery processes and its potential applications. Although the structure and biosynthetic pathway of lignin have been studied for more than a century, they have not yet been completely elucidated. In this mini‐review, the primary obstacles to elucidating the structure of native lignin, including separation and characterization, are highlighted. Several classical methods for separation and various NMR techniques, especially 2D HSQC NMR, for characterization of lignin are reviewed. Some potential applications of lignin are introduced. It is believed that a knowledge of the method to separate lignin from the cell wall and structural features of the lignin polymer from lignocellulosic materials will help to maximize the exploitation of lignocelluloses for the biorefinery as well as the utilization of lignin for novel materials and chemicals. © 2012 Society of Chemical Industry