Cork: Current Technological Developments and Future Perspectives for this Natural, Renewable, and Sustainable Material

Cork is the bark of Quercus suber L., the cork oak tree. It is currently explored for different industrial applications, of which stoppers for the wine industry is the most representative and economically important. During the processing stages, up to 30% of cork is transformed into powder, which is mainly used for energy production by the industry. This underexploited natural resource stream constitutes an opportunity for the development of new products. In this review, we discuss cork as a potential source of chemicals for alternative applications. Special emphasis is dedicated to (a) suberin, (b) the extractives fraction, and (c) the use of cork in nontraditional applications. Suberin constitutes a source of long chain hydroxyacids which can serve as building blocks for new macromolecules and materials. The structure and composition are briefly addressed, while the advances in suberin depolymerization, extraction methodologies, and the proposed applications for this material are thoroughly discussed. The extractives fraction is constituted by lipophilic and phenolic compounds that present strong antioxidant and biological activities. The extractives composition and its properties are addressed. Finally, the use of cork for recently proposed applications, such as the preparation of activated carbons and as templates for the adsorption of pollutants, are also presented. This review is intended to summarize the current knowledge and technological development state and to push for the progress toward an integrated cork economy.