Lignin is produced as a byproduct in cellulosic biorefinery as well in pulp and paper industries and has the potential for the synthesis of a variety of phenolics chemicals, biodegradable polymers, and high value-added chemicals surrogate to conventional petro-based fuels. Therefore, in this critical review, we emphasize the possible scenario for lignin isolation, transformation into value addition chemicals/materials for the economic viability of current biorefineries. Additionally, this review covers the chemical structure of lignocellulosic biomass/lignin, worldwide availability of lignin and describe various thermochemical (homogeneous/heterogeneous base/acid-catalyzed depolymerization, oxidative, hydrogenolysis etc.) and biotechnological developments for the production of bio-based low molecular weight phenolics, i.e. polyhydroxyalkanoates, vanillin, adipic acid, lipids etc. Besides, some functional chemicals applications, lignin-formaldehyde ion exchange resin, electrochemical and production of few targeted chemicals are also elaborated. Finally, we examine the challenges, opportunities and prospects way forward related to lignin valorization.

木质素是纤维素生物精炼厂以及纸浆和造纸工业中的副产品，具有合成多种酚类化学品，可生物降解的聚合物和替代传统石油基燃料的高附加值化学品的潜力。因此，在本次重要评论中，我们强调了木质素分离，转化为增值化学品/材料以实现当前生物精炼厂的经济可行性的可能方案。此外，本综述涵盖了木质纤维素生物质/木质素的化学结构，木质素在全球范围内的可获得性，并描述了各种热化学方法（均相/异质碱/酸催化解聚，氧化，氢解等）以及用于生产生物基低碳的生物技术发展。分子量的酚醛树脂，即聚羟基链烷酸酯，香兰素，己二酸，脂质等。此外，还阐述了一些功能化学品的应用，木质素-甲醛离子交换树脂，电化学和少量目标化学品的生产。最后，我们研究了木质素增值相关的挑战，机遇和前景。