Sustainable packaging from pine mirror bark

From by-product to material

Packaging in Europe still contains a substantial share of virgin, non-recycled materials and makes a significant contribution to municipal solid waste. At the same time, awareness of sustainable alternatives is growing. In her bachelor’s thesis at the TUM School of Life Sciences, Paula Röser therefore investigated a material that is already generated in wood processing: the mirror bark of Scots pine.

Bark accounts for around 10 to 20 percent of tree biomass, yet it is still largely only used for energy recovery, for example by burning at sawmills. Industrial debarking usually produces bark in the form of small chips. Larger material applications therefore require suitable binding strategies. This is precisely where Röser’s work comes in: she investigated whether thin pieces of pine mirror bark can be bonded using only water, pressure and heat.

Bonding without additional adhesives

For her experiments, Röser first soaked bark strips in distilled water, then pressed them under moderate pressure and heated them to 60, 90 or 120 degrees Celsius. The results were particularly promising at 60 degrees Celsius, where all samples formed a bond. Surface orientation also proved decisive: samples with the cambium sides facing each other showed markedly higher bonding success than samples bonded via the outer rhytidome surfaces.

A promising approach for sustainable packaging

Mechanical testing revealed considerable variability, as is typical for heterogeneous natural materials. In several cases, however, the bond strength approached the intrinsic strength of the bark itself. Further research is needed before practical application, including investigations into pressing time, pressure, water resistance and material variability. Still, the fact that bonding was achieved at comparatively low temperature and moderate pressure points to a manufacturing approach with low energy demand.

The thesis was supervised by Prof. Dr. Michaela Eder, Professor of Wood Science and Functionalization at the TUM School of Life Sciences in Freising, and Prof. Dr. Cordt Zollfrank from the Professorship for Biogenic Polymers at the TUM Campus Straubing. Röser’s research demonstrates the potential of pine mirror bark as a raw material for sustainable, adhesive-free packaging solutions.

Awarded by the Sattelmühle Foundation

The bachelor’s thesis was recognized by the Sattelmühle Foundation, which supports science, research and education, with a particular focus on environmental, nature and climate protection, landscape conservation, forestry and environmental sciences. The award ceremony took place on Friday, 26 September, at the foundation’s Forstgut Sattelmühle in the Palatinate Forest. Through its awards, the foundation honors outstanding bachelor’s and master’s theses as well as dissertations.