The potential use of lignin as a platform product in biorefineries: A review

Lignin is widely available in biomass sources, and the aromatic structure can justify its use as a precursor or platform for obtaining value-added compounds. However, lignin is considered a low-price by-product or low-value fuel for energy recovery in the pulping industries. Therefore, the development of technologies and methodologies that promote the valorization and efficient utilization of this biopolymer becomes an essential aspect of biobased processes, especially in biorefineries. This review shows the opportunity to target lignin as a marketable by-product for value-added chemicals through thermochemical, chemical, and biochemical pathways, with or without the absence of catalysts. Likewise, the valorization of lignin includes emerging technologies to produce carbon and polymer materials. This work also emphasizes the description of technical, economic, and environmental aspects that would affect lignin in different biorefinery stages. Therefore, a discussion based on current studies and evaluations of lignin valorization processes is considered. Finally, a preliminary techno-economic and environmental assessment of a wood-based biorefinery was performed as an example to better understand the importance of lignin as a platform product in biorefineries. It includes the processing scale analysis over ten years of the project lifetime. The review established the importance of lignin valorization to increase biorefineries efficiency and sustainability.