Lignin Valorization and the Opportunities of Retaining its Natural Structure.

Abstract

The chemical industry's dependence on fossil carbon increasingly raises major sustainability concerns. Lignocellulosic biomass is a promising alternative resource, but it has been historically difficult to valorize to chemicals, especially in a way that is economically profitable. The lignin fraction has been particularly challenging to use even though it is nature's largest source of aromatic functionality, notably because conventional lignin extraction methods cause severe condensation, limiting subsequent depolymerization and functionalization. Recent lignin-first technologies address these challenges through active lignin stabilization during fractionation, enabling the high-yield production of oxygenated aromatic monomers. This review summarizes strategies for preserving native lignin structures and explores their conversion into chemicals, polymers, and bioactive molecules. We emphasize emerging opportunities to leverage lignin's intrinsic functionalities to enhance atom economy, reaction efficiency, and final product safety and performance. We suggest that leveraging natural functionality leads to these benefits, which go beyond simple circularity, and could ultimately push and enable adoption of this more sustainable feedstock in the chemical industry.