Humins: Still-unknown antagonists in polysaccharides valorisation

Among the primary objectives of modern biorefineries is the production of furfural, hydroxymethyl furfural, and their derivatives, which are key 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 are highly cross-linked macromolecules of complex nature with limited technological applications. This editorial offers a brief overview of the “humin issue”, discussing the challenges posed by these materials from an analytical perspective. Despite considerable efforts towards their characterization, the structure of these materials remains largely unresolved, representing an ongoing challenge for green chemistry and the optimization of biorefinery processes.