Europe joins hands to curb forestry waste

The whole shell of the needle wood can be utilized by the new process.

A consortium of European companies has been formed to collaborate on bringing into industrial production a new process for full utilisation of softwood bark.

Using the new method a high yield of pure tannins can be extracted from the bark for use as a raw material for resins used in wood products. The residual fibre fraction can be used to produce sugar as a raw material for fermentation products. It is also suitable for material applications.

In the mechanical and chemical forest industry in Finland alone, 3 million tonnes of softwood bark are produced annually, which are presently mainly used for energy production.

The method for the total utilisation of the bark has been developed by Finland-based VTT, Europe’s leading research, development and innovation organisation,

It forms a part of the European Union’s project, ‘Systemic Approach to Reduce Energy Demand and CO2 Emissions of Processes that Transform Agroforestry Waste into High-Added-Value Products’.

Traditionally, tannins are extracted from the bark by hot water extraction. In addition to tree species, the extraction yield is influenced by the origin and processing history of the raw material.

From Scandinavian spruce and pine, the yield remains at most 10% of bark weight. The utilisation of bark residues as a source of sugar has been studied through enzymatic hydrolysis.

The yields have not been very high, and consequently much of the bark tannin and carbohydrates have remained unutilised. But the new process uses much higher alkaline conditions and a higher temperature, more closely resembling the wood cooking process.

About one-third of the bark weight can be dissolved and isolated as a tannin fraction with significantly less impurities – carbohydrates and ashes – than in a fraction obtained by hot water extraction. This tannin extract is a much more reactive resin raw material than normal kraft lignin.

The same technology as used for lignin recovery is suitable for the recovery of tannin. The fibre fraction can be hydrolysed considerably more easily than after hot water extraction.

The consortium, comprising of BBEPP from Belgium, Foresa from Spain, Bio Syncaucho and Tecnalia from Spain is expected to include an interested supplier of raw material, equipment supplier and application testers to utilise the tannin and fibre fractions.

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