Recent advances, challenges, and opportunities in lignin valorization for value-Added chemicals, biofuels, and polymeric materials

Lignin, an abundant and renewable resource, is increasingly important for renewable energy and sustainable development. Recent attention has focused on producing value-added chemicals, biofuels, and polymeric materials from lignin. This review discusses the processes for generating value-added chemicals via catalytic depolymerization, detailing the methods, mechanisms, and catalysts involved. It also covers the conversion of depolymerization products into compounds like vanillin, phenol, benzoic acid, and fatty acids through dehydrogenation, demethylation, and microbial fermentation. In biofuel production, the review systematically examines techniques for transforming lignin into transportation fuels, such as biodiesel and aviation fuel, as well as high-energy–density fuels through hydrodeoxygenation. Additionally, it addresses lignin-based polymeric materials, including epoxy resins and thermoplastic polyurethanes, emphasizing functional group modification techniques that enhance their properties compared to petroleum-based alternatives. The review identifies current technological barriers and emerging research directions to improve the efficient conversion of lignin into value-added products, aiming to advance its industrial applications.