Humins: Still-unknown antagonists in polysaccharides valorisation

Among the primary objectives of modern biorefineries is the production of furfural, hydroxymethylfurfural, and their derivatives, which arekey compounds for the synthesis of widely used fine chemicals, including plastics and other everyday materials. However, the industrial development of these processes is hindered by the formation of unwanted by-products, most notably humins. Humins arehighly cross-linked macromolecules of complex naturewith limited technological applications. This editorial offers a brief overview of the “humin issue”, discussing the challenges posed by these materials fromananalytical perspective. Despite considerableefforts towards their characterization, the structure of these materials remains largely unresolved, representing an ongoing challenge for green chemistry and the optimizationof biorefinery processes.