"Cellulose is by far the most abundant organic raw material on earth, and has the potential to become a super-material of the future", says Professor Herbert Sixta, Head of the Department of Forest Products Technology and leader of the Biorefineries Research Group at Aalto University in Espoo, Finland.
Sixta stresses how our oil-based economy and its products must gradually be replaced with the bioeconomy and renewable raw materials in order for us to survive. This fact is the driving force behind Aalto University's ongoing research efforts to optimize and develop processes for separating value-added products such as cellulose, hemicellulose and lignin from biomass. Cellulose is well suited for modification and multiple uses for the good of mankind, even though Sixta admits that the material has certain challenging characteristics.
"The difficult thing with cellulose compared to synthetic polymers is that it is extremely difficult to process. It is a multifunctional polymer with good basic properties, but with limited solubility. Because of this fact, it is quite understandable that so far we only have pulp and paper as larger volume products. We already have textile fibres, and a few other cellulose derivatives such as acetates, but compared to the overall volume of paper they have only niche functions," Sixta says.
He sees the textile industry as a highly potential and significant business for adopting cellulose fibres as replacements for synthetics.
"Textiles have a high market volume of around 100 billion tonnes per year, which is in a similar order of magnitude to paper. At the same time the use of cotton cannot be further increased due to the fact that it competes with arable land needed for the cultivation of food. These conditions are in favor of, for instance, wood-based cellulose products," Sixta explains.
Pioneering pulp expertise
A Professor at Aalto University since 2007, Sixta also holds an additional post in his native country Austria as a Professor in the field of chemical pulping at the University of Technology in Graz. He started out at the University of Innsbruck in Austria studying chemistry, and obtained a PhD in 1982. However, most of his early career was spent at Lenzing AG, a company specialized in the production of regenerated cellulose fibres. At Lenzing he established a research department mostly focused on pulp chemistry and technology.
"My academic career re-started in the 90's when I became Associate Professor in Graz. As a scientist and researcher I have mainly been involved in the areas of dissolving pulp, cellulose chemistry and regenerated cellulose products. But I expanded this scope to lignin chemistry and also worked on hemicellulose valorization," Sixta says.
These days his research group consists of 21 PhD students working on a varied range of expert subjects related to bio-based material research.
"Our focus as a department is still on improving pulping processes and the properties of pulp, which continue to be key issues around the world. We have, for instance, recently worked on a joint project on traditional kraft pulping with the Metsä Group where we managed to substantially increase the yield of pulp."
Sixta says he is one of the last few researchers with a similar background to many of the previous experts at Aalto University back in the day when there was no distinction made between the fields of pulping and regenerated cellulose fibres.
"Finland certainly belongs to the pioneering countries in pulping and has made many important inventions, especially in engineering. Aalto University used to also be very well known for the chemical recovery in kraft pulping, but unfortunately this expertise has more or less been lost," Sixta says.
Huge potential in textiles
According to Sixta, one of the milestones in processing cellulose for value-added applications is the discovery of so-called ionic liquids as powerful cellulose solvents. By using ionic liquids it is possible to separate certain fractions of molecules from pulp. Hemicellulose can thus be isolated to produce dissolving pulp from paper-grade pulp. Dissolving pulp can then be spun into textile fibres such as viscose or lyocell, or utilized in non-woven technical or chemical applications.
Market volyme of textile industry: 100 billion tonnes per year
Taking a step further, Aalto University took part in the FuBio Cellulose research programme led by the Finnish Bioeconomy Cluster FIBIC Oy, together with a group of other universities and companies, including Metsä Fibre. In a joint effort with a group from the University of Helsinki, the project resulted in a major breakthrough in the summer of 2013, with the discovery of a new type of ionic liquid. The solvent revealed highly stable spinning conditions, which led to excellent quality fibres.
When a sample scarf was knitted from the fibres produced by the novel Ioncell process and after the Finnish design company Marimekko showed interest in the material, a concrete result was displayed in the form of a dress made from birch fibre, launched in March 2014 at Marimekko's fashion show.
Now that the dissolving and regeneration process has been proven to be stable and simple, the next step is to find a way to recycle the solvent.
"We started later with this part of the process, and while there are certain obstacles, I believe we can tackle them. Basically, we have to be able to recycle close to 100 percent of the solvent. Only then can we seriously consider this process as a candidate to be up scaled. It will take a while, but step by step we are approaching the level where we could be considered an interesting partner for the pulp industry," Sixta says.
Research ready for the next level
In many ways the pulp industry is ideally positioned to contribute significantly to the bioeconomy. Although the existing pulp technology has its roots in the 19th century, the industry has excellent potential to continue to make innovative use of its renewable raw material.
In many ways the pulp industry is ideally positioned to contribute significantly to the bioeconomy
According to Sixta, in the case of taking cellulose fibres to the next level in textile production, it all depends on the available resources. Refining bio-based materials is a very resource intensive business.
"We would of course be able to do the academic research, but lack the resources for scaling it up. We would need to produce certain amounts of final products, which would then have to be tested by selected clients for feedback. Also, marketing efforts would need to be launched at the same time."
If it was up to Sixta's group, he believes they could deliver the necessary databases for a pre-study, which could then provide the basis for a managerial board to decide whether to invest in the next level. This would be a pilot plant producing around 1 to 5 tonnes of fibres per day, amounting to a value of roughly 20-30 million euros.
Despite the positive buzz around the bioeconomy and its elevated status as one of the Finnish Government's key projects, the situation regarding the project's funding is currently uncertain.
"We, of course, appreciate the support of forest companies and public funding agencies, but there is a gap in taking things to the next level. This is partly due to the fact that Finnish companies don't have their own strong R&D departments in this field anymore, where our knowledge could be built upon and scaled up."