Bark extractives as sources of carbon-efficient functional precursors and materials

<p>Biomass residues generated in forest operations represent an abundant and renewable resource in need for valorization. Bark is becoming increasingly relevant, not only in the bioproducts sector, but also in the context of the circular bioeconomy, which is placing emphasis on underutilized residues and waste. Among these, tree bark is one of the largest forestry by-products, accessible at a megaton scale but so far mostly utilized for its solid fuel value. Bark valorization should include the isolation of valuable natural compounds that add functionalities to a variety of bioproducts. This is the subject of this review, which considers bark extractives prospects, under the biorefinery concept, placing attention on extractives' chemical profiles and properties. We introduce the most recent pathways reported for bark fractionation and the opportunities to achieve new materials by using the concepts of supramolecular chemistry, leading to special assemblies. We show that value-added chemicals and materials are possible and expected to become most relevant in efforts aimed at maximizing bark utilization.</p>