Dear Colleagues,

I am very pleased to invite you to contribute to a Special Issue of the Journal of Applied Sciences, “Bio-Materials in a Bark Biorefinary Context”.

Bark is considered the outermost layer of stems and roots of woody plants and mainly consists of the inner and the outer bark. Bark undertakes essential roles in a living tree, namely, serving as a first line of defense toward external aggressive agents, water equilibrium, and nutrient transportation.  

Bark is an underused waste residue from forest biomass and an inexpensive renewable resource present in large quantities, being responsible for disposal problems in forest operations, and must be continually moved out of mill sites in the wood, pulp, and pulp industries.

There is huge potential for converting bark into value-added products due to its complex and highly heterogeneous chemical composition. However, this chemical upgrade, in a biorefinery context, is somewhat limited and challenging. Barks chemical composition contains relatively high amounts of extractives (polar and non-polar extractives) when compared to wood, higher lignin content, and less holocellulose. Polar extractives (flavonoids, phenolics, glycosides, tannins, sugars, and so on) are typically three to five times more abundant than non-polar compounds, including waxes, resins, lipids, unsaturated fats, sterols, terpenes, and so forth. Barks fractionation into divisions with distinctive polarity can be achieved through successive extractions applying a combination of organic solvents and hot water. Lignin and polysaccharides are analyzed by a first extraction with aqueous alkali solutions, followed by hydrolysis of the extractive-free bark by sulfuric acid to give Klason lignin and acid insoluble residue contents.

Developing new processes that can extract, isolate, and purify these high value chemicals and other products is the main focus of research within a “Green Biorefinery” context.

Dr. Joana Ferreira
Guest Editor

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