New research shows that we can increase the number of times that paper can be recycled, something that could revolutionise the paper industry. Björn Sjöstrand, Associate Professor in Chemical Engineering at Karlstad University, has devoted many years to understanding and improving the process of removing water from wood fibres in paper production. In October, he will be in attendance as a speaker at Scanpack Pioneers, where he will explain how his research can make paper production more sustainable and resource-efficient.

Paper production is expensive and requires a lot of energy. To make the paper industry more sustainable, we need to know more about how the water can be removed from the wood fibres used in paper production. Björn Sjöstrand has devoted a considerable number of years to figuring out how to achieve this.

Crucial to how many times the material can be recycled

Paper is made from wood fibres. These are good at some things, but less good at others. For example, they are good at clumping together and retaining water. However, what we need of course is flat paper and, to achieve this, the pulp is watered down using large quantities of water, particularly at the start of the production process. The next stage is where the paper machine removes the water content.  Hornification occurs when wood fibres are unable to regain their original appearance, behaviour and structure after the material has been dried. Understanding how hornification and water affect these materials is crucial to production efficiency, recyclability and optimisation of resource usage for various paper and cardboard materials.

‘You see, hornification is the major change that takes place after each drying process, limiting the number of times you can reuse the material,’ Björn Sjöstrand explains.

Successful results may treble recycling

In an article, he has shown that hornification can be prevented, which in practice means that the material can be reused several times.

‘If we succeed in counteracting hornification, we can double or even treble the number of times a material can be reused. Instead of the material being able to handle five to seven cycles, we can perhaps go as far as ten to fourteen. This part of the process focuses more on resource efficiency and recyclability than on energy efficiency. And I’ll be talking more about this at Scanpack this autumn,’ Sjöstrand explains.

Unclear how the phenomenon occurs

While we do know what hornification is caused by, exactly how this phenomenon occurs remains unclear. This deeper insight will be needed in order to improve industrial processes and enable innovative solutions and the upscaling of new processes that currently work only in the laboratory environment.

‘We believe that hornification is caused by chains of water molecules binding to each other with hydrogen bonds. These bonds, which look like overlapping Mickey Mouse figures, are weak when they are in water form. When the water is then removed, the chains draw together the cellulose surfaces and create stronger bonds between them. We don’t know exactly what bonds arise, but we have seen that this drawing together of the cellulose surfaces when the water is removed must be due to hydrogen bonds. When we replace the water with alternative solvents, such as methanol, ethanol, isopropanol, acetone and ethyl acetate, hornification occurs to a much lesser extent – sometimes not at all.

‘Understanding how hornification and water affect these materials is important for improving production efficiency, recyclability and resource usage in paper and cardboard production. By studying these processes, we can save a lot of energy and, at the same time, find new applications for forest-based materials,’ Björn Sjöstrand believes.

From lab tests to the factory

So far, tests have taken place only in laboratories. The next step will be to perform tests out in the factories. But this comes with challenges, he explains:

‘Just because something works in a laboratory doesn’t always mean it will work on a real machine. This is why we work on four scales: laboratory, pilot scale, full scale and data simulations. I work mainly on the laboratory and pilot scales, with full scale being the last stage where we test on real machines.’

There are four recurrent points of attack in Björn Sjöstrand’s research: energy efficiency, resource efficiency, recyclability and the replacement of fossil materials with biobased alternatives.

‘At the moment, I’m particularly involved with the first three issues, particularly in terms of resource and energy efficiency as well as recyclability with regard to hornification. But, if we can also understand the process and how it works in more detail, we can introduce new materials, such as micro and nano-fibrillated cellulose in paper-like processes. Materials that can be transparent and very malleable, opening up options for new areas of application. Water removal and hornification will play an important role in this context, too.’

Common goals

A lot is happening in the paper industry right now. And Björn Sjöstrand believes that there is a desire to pull in the same direction, towards the same goals.

‘In a way, this is right at the core of why I go to work in the morning, and why it’s such fun. We’ve so many projects on the go where the industry really wants to work together.’

In October, Björn Sjöstrand will be in attendance as a speaker at Scanpack, the meeting place for the Scandinavian packaging industry. Scanpack will take place from 22–25 October at the Swedish Exhibition and Congress Centre in Gothenburg. Find more information about the programme here.