Wood is widely used for the production of everyday goods such as building materials, furniture, packaging materials and even textiles. Bark, which makes up 10-15% of a tree trunk, is a byproduct of wood processing and has only current value in energy production. What if softwood bark could be turned into a valuable source of bio-based chemicals needed to make high-quality wood products? This is the vision behind SuperBark and in this article we look at how they can extract biobased chemicals from bark.
Bark polyphenols for bio-based adhesives. Photo: Elisa Spönla, VTT
Abundant but underutilized
Softwood bark is an underutilized biomass source, with an annual production of 14 million tonnes within the EU. This bark contains valuable polyphenolic compounds, such as condensed tannins. Instead of burning bark for energy, the SuperBark project aims to convert this bark into bio-based chemicals to replace fossil and harmful chemicals that are now widely used in coatings and adhesives.
However, the use of coniferous bark for chemical production is hampered by the lack of suitable processing technologies. Traditional extraction methods, such as hot water extraction, produce chemicals with low yield and purity. New technologies are therefore needed to effectively valorize this bark.
Despite its abundance, the use of softwood bark in chemical production is hampered by the lack of suitable processing technologies. Traditional bark extraction techniques, such as hot water extraction, have produced chemicals with low yield and purity. New processing technologies that can overcome the bottlenecks of traditional techniques are therefore needed to enable the valorization of softwood bark into chemical products.
Polyphenols for biobased adhesives
In Work Package 2 (WP2), VTT Technical Research Center of Finland uses a patented alkaline extraction process to extract valuable polyphenols from coniferous bark. This process offers higher yield (~25% on dry bark) and purity than traditional methods. The project evaluates softwood bark from Finland and Turkey as raw material. An important goal is to develop an extraction process that produces high-quality polyphenols, suitable for adhesive production.
Seven months after the start of the project, the first batches of polyphenols on a kilogram scale have been produced from Scandinavian spruce bark. These polyphenols have been supplied to partners for the development of adhesives. Various extraction and recovery methods have been performed, resulting in polyphenols with diverse chemical compositions. Feedback on the performance of these polyphenols is used to further improve extraction processes.
1. Side stream of wood bark, used for the extraction of biobased chemicals. 2-4. Processing of bark nanocellulose for biobased coatings. Photos: Jenni Rahikainen, Panu Lahtinen, VTT
Full use from bark to materials
New biorefinery processes must be aimed at full utilization of the raw material. The remaining cellulose-rich bark residue after the alkaline extraction is therefore evaluated for nanocellulose production. Nanocellulose is a versatile bio-based material that can improve the mechanical or barrier properties of coating and adhesive formulations.
WP2 has produced bark nanocellulose from the residue of spruce bark. VTT can adjust the properties of this nanocellulose, such as polyphenol content and viscosity. These nanocellulose grades have been sent to partners for evaluation, especially for coating formulations. Feedback from these partners is used to further tailor nanocellulose production to the desired end applications.
By fully utilizing bark and converting it into valuable bio-based chemicals and materials, SuperBark can contribute to a more sustainable and efficient wood processing industry.
About SuperBark
SuperBark researches components in softwood bark to develop new bio-based adhesives and coatings for a range of industrial applications. The four-year project (September 2023-August 2027) will improve the sustainability, health and safety profiles of adhesives and coatings products compared to fossil-based solutions.
Source: Superbark.eu
