– Long fibers produce strong paper and cardboard products due to an increased number of bonds, says Björn Sjöstrand, Associate Professor of Chemical Engineering at Karlstad University. The advantage of increased strength broadens the range of applications, and the same strength can be achieved with less material.

The hypothesis for the study was that trees with fast height growth may have longer fibers, and thus provide longer pulp fibers, compared to lengths previously reported in Sweden.

The fiber length study was recently published in the scientific journal Holzforschung. Results indicate that many long fibers can be formed in trees that grow fast in height, and even at a relatively young age. The study also shows that the so-called mode value appears to be more stable and better suited to characterize fiber length compared to mean and median values. This measure of central tendency could complement current specifications used to characterize pulp.

The findings are promising for identifying or cultivating forests versus a higher proportion of long fibers in the future.

The sample material comes from a forest on bedrock called hyperite, and a well known fertile forest site located north of Karlstad. The forest’s annual volume growth is about four times the national average. Sweden’s tallest known trees of eg. spruce, over 49 meters, grew there until a few years ago. Further analysis of explanatory variables and other wood properties is ongoing.

– Although the scope of the study is relatively limited, the results align with hypotheses proposed internationally, says Armas Jäppinen, affiliated researcher at the Department of Engineering and Chemical Sciences at Karlstad University. If our fiber length findings prove to be more general and apply to other forests with similar management and favourable growth conditions, the advantages could be significant.

The research was conducted through interdisciplinary collaboration, which proved to be a strength. Armas Jäppinen, PhD in Forest Products, identified and selected samples and collected the wood together with Mikael Perstorper, Adjunct Professor of Building Technology at Karlstad University. Carl Moser, postdoc at KTH, processed the wood into pulp, and Björn Sjöstrand analyzed the fibers. Complementary studies on the properties of sawn timber from the material are ongoing.

The research is part of the Pro2BE environment, Processes and Products for a Circular Bioeconomy, at Karlstad University. Pro2BE focuses on research and education for the transition to a bioeconomy based on sustainable and renewable resources, as well as the development of the forest industry.

Read more here: Fiber length characteristics of Norway spruce (Picea abies) trees with fast height growth