Scaling Up Bark Valorisation in SuperBark

The basis of the SuperBark valorisation concept is the alkaline extraction technology that fractionates bark into functional high-value components. This process has been tested successfully for multiple bark types and processing conditions, and the most promising extractions were successfully scaled up. 

How bark is fractionated 

During alkaline extraction, crushed bark is treated in water-based alkaline conditions at high temperatures. This causes polyphenols, mainly tannin and lignin, to dissolve into the liquid phase. After separation of the solid and liquid phases, two fractions are obtained: 

• A polyphenol-rich extract, which is further processed into dry polyphenol powder suitable for adhesive applications 
• A cellulose-rich bark residue, which can be further valorised for different applications, such as cellulose nanofibrils (CNF) suitable for coating applications.  

This patented technology provides significantly higher polyphenol yields from softwood bark compared to conventional water extraction methods.   

Studying softwood barks from northern and southern Europe 

SuperBark focuses on softwood bark side streams of Norway spruce, Scots pine, and Calabrian pine that were collected from forest industry plants in Finland and Türkiye. These raw materials differ naturally in their chemical composition and structure, influencing both processability and product yield and quality. All three barks were processed under milder and harsher extraction conditions with varying temperatures and alkali doses, producing polyphenols with different properties. Simultaneously, the resulting bark residues were further processed and converted to different grades of CNF. The samples were shared with the project partners to collect feedback on their performance in the formulation of adhesives and coatings. 

Pilot-scale success: a major milestone 

One of the most important achievements in SuperBark has been the successful pilot-scale extraction of selected bark types. The process was scaled up to a 130-litre reactor, demonstrating performance at Technology Readiness Level 6. At pilot scale, spruce and Calabrian pine barks were processed with optimised conditions, resulting in high yields of polyphenol-rich powders and cellulose-rich residues. These trials confirmed that the process works reliably at a larger scale and increased the total amount of polyphenol powder produced within the project to over 30 kg. 

Currently, industrial partners such as Metsä Wood and Kastamonu Entegre are actively testing wood panels that contain the adhesives developed in the project by research partners. The studied application areas for polyphenol-based adhesives are plywood, particleboard, and medium-density fibreboard (MDF), while CNF-containing coatings are tested for wood-based products and barrier coatings for paper-based packaging.  

SuperBark has now demonstrated that softwood bark can be efficiently fractionated at pilot scale into valuable components. These results lay a strong foundation for further scale-up and future commercial deployment of bark-based materials.  

More detailed information on the bark extractions in pilot scale will be published later in a dedicated report.