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2.7 Bark biorefinery; fundamental insights on the properties of a novel organosolv lignin from Norway spruce bark

Maria Karlsson, Isabella Kwan, Barbara Rietzler, Monica Ek, Martin Lawoko

Wallenberg Wood Science Center, Department of Fibre and Polymer Technology, KTH Royal Institute of Technology

The use of renewable biomaterials in our every-day life to replace fossil-based compounds is gaining more and more attraction. Bark is usually seen as a waste product in the wood and pulp industry and is burned for energy production. However, bark can be more economically beneficial as it contains not only cellulose but also hemicellulose, lignin, and other valuable compounds. In recent years, bark-based biorefinery concepts have emerged [1].

This project focused on extracting lignin from Norway spruce bark via a novel cyclic organosolv extraction of lignin [2], subsequent to removal of extractives and polysaccharides. Furthermore, residual-bark lignin was characterized by 1D and 2D NMR techniques, and size exclusion chromatography. High β-O-4' content and low amounts of condensed phenolic hydroxyl functionalities indicated that the lignin recovered was structurally preserved. The lignin also exhibits features of high purity and low polydispersity. Extractives such as pectic polysaccharides and hemicellulose were also recovered with minor degradation. Overall, useful molecules with potential for bio-based products are obtained.

[1] M. Le Normand, R. Moriana and M. Ek, Cellulose, 2014, 21, 4583-4594
[2] M. Karlsson, N. Giummarella, P. A. Lindén and M. Lawoko, ChemSusChem, 2020, 13, 4666-4677