Lignin is a renewable aromatic resource and the most abundant aromatic biopolymer on Earth. As a byproduct of paper pulping, more than 50 million tons of waste lignin is generated annually and used primarily for heat and supplemental energy through simple combustion. Lignin production is also expected to increase as a byproduct of lignocellulosic biofuel industries. Thus, demand on effective lignin valorization technologies is increasing. Although many attempts have been made to develop lignin valorization technologies based on thermochemical or biological processes, efficient degradation of lignin and upgrading to value-added products remain challenging. This paper reviews recent developments and the advantages and/or drawbacks of each thermochemical depolymerization and biological conversion process, and explores the possibilities for sustainable industrial application of waste lignin using an integrated valorization method that combines thermochemical depolymerization and biological conversion. Furthermore, various value-added products such as vanillin, muconic acid, polyhydroxyalkanoates, and lipid representing as comprehensive proof of concepts for great potentiality of lignin are thoroughly discussed.

木质素是可再生的芳香资源，也是地球上最丰富的芳香生物聚合物。作为纸浆的副产品，每年产生超过5000万吨的废木质素，主要通过简单燃烧将其用于热能和补充能源。作为木质纤维素生物燃料产业的副产品，木质素的产量也有望增加。因此，对有效的木质素增价技术的需求正在增加。尽管已经进行了许多尝试来开发基于热化学或生物过程的木质素增价技术，但是木质素的有效降解和升级为增值产品仍然具有挑战性。本文概述了每个热化学解聚和生物转化过程的最新发展以及优缺点，并探索了将热化学解聚和生物转化相结合的综合价值评估方法来实现废弃木质素可持续工业应用的可能性。此外，还详细讨论了各种增值产品，例如香草醛，粘康酸，聚羟基链烷酸酯和脂质，它们是木质素潜力巨大的概念的全面证明。