Scientific breakthrough hopes to increase the recycling capability of paper significantly
Swedish researchers have found a way to hinder the biggest limiting factor for recycling.
4 Mar 2024

Dr Björn Sjöstrand is Associate Professor Chemical Engineering at Karlstad University. In a scientific project, he and his team have studied wood pulps, intended for paper manufacturing, and what happens to the wood fibres during dewatering and drying. 

— In this particular project we focus on hornification, which is when wood fibres are unable to reswell in water after they have been dried, he explains. The project is mainly driven by our curiosity of this very interesting material — the wood fibres — and our optimism to contribute to a sustainable future, and the results are hopefully interesting for the global forest industry. These results contribute to a green transition to a circular forest-based bioeconomy through more efficient processes and use of raw materials, enhanced recycling, as well as increased understanding of scaling up in the manufacturing of new forest-based materials.

You’ve now experienced a breakthrough. What have you come up with?

— We have found a way to hinder the phenomenon hornification of commercial hardwood and softwood pulps in laboratory scale. We also know a great deal more about the underlying mechanisms than we did before. 

— Hornification is the major limiting factor for paper recycling. It makes the wood fibres for paper production stiffer, less flexible, and less able to form fibre-fibre bonds which are crucial for the strength and integrity of the paper products. Hornification limits the number of recycling cycles for fibres to around 5-7. It also lowers strength properties of dried pulps, increasing the need to use more raw material to achieve certain strength properties. When developing new applications for cellulosic materials, hornification also often becomes a limiting factor affecting the performance of the newly designed materials.

Sjöstrand’s own picture of a regular paper, using SEM (scanning electron microscopy).

What industries and what industry players can benefit from the findings?

— Knowledge about hornification and water interactions of wood fibres in manufacturing processes will be able to save great amounts of energy in paper manufacturing, and manufacturing of other materials from cellulose raw materials. The results will enable new strategies for enhanced pulp drying where strength properties are maintained. They will also increase the number of times paper can be recycled, if we are able to impede hornification also in full industrial scale, we estimate that each wood fibre will be able to be recycled many more times than the current estimation of 5-7 times. This will not only be crucial in pulp and paper manufacturing but also in new materials from cellulosic sources, such as textiles, filaments, composite materials, membranes etc.

What are the next steps here?

— As always, new results also raise more questions. Whenever we answer one question and get exciting results, something like five or ten new research questions emerge. This can sound disheartening of course, but it is really why research is so exciting! Sjöstrand states. He continues:

— We have only scratched the surface, even with our breakthrough findings, and are currently applying for more funds to continue our work with hornification. Next step would be to address all the new research questions we have found, and also to cooperate with pulp and paper manufacturers to see if we can achieve the same things as in our labs, in an industrial setting. We also have ideas for many more experiments in the lab to further our knowledge about the phenomenon.

Will you also work to bring the solution to market?

— We have had industrial partners in all stages of the products, and are also publishing all our results Open Access, and we hope that as many producers and companies as possible get hold of our results and make them useful. We would be very happy if we could be helpful for companies to increasing paper recycling, minimising the use of raw materials, and that they are enabled with more possibilities for new cellulosic-based materials that are renewable, reusable, recyclable, and biodegradable.