Unlocking the potential of tree bark: Review of approaches from extractives to materials for higher-added value products

The harvest of trees typically results in the availability of bark biomass as raw material. In 2021, it is estimated that the wood processing sector produced approximately 200 million cubic meters of bark. Despite being commonly regarded as waste or a low-value by-product, this sustainable raw material possesses appealing properties because of its intricate chemistry and structure, which serve as a multifunctional barrier for living trees. Consequently, the majority of studies on the utilization of bark have focused on the extraction of valuable chemical compounds and bioactive agents. A biorefinery approach for bark was proposed to improve the efficiency and economic feasibility of bark utilization. However, relatively few studies have been dedicated to the exploration and enhancement of bark-based products, particularly structural materials. Therefore, this review aims to describe the potential applications that exploit the chemical and physical properties of bark, with an emphasis on structural materials. A brief overview of the structure and chemistry of tree bark is provided, followed by an examination of physical characteristics such as density, mechanics, thermal properties, and caloric value. Finally, the potential applications of bark biomass as a structural material are discussed.