Published 13 April 2018 by Ben Nasli Bakir
I’ve been working in R&D for over 30 years, and lignin has always been of great interest. Not just to me, but to many of us working closely with wood fibres and chemicals, and concerned about finding alternatives to oil-based materials.
Lignin (Lignum) means wood in Latin, and it’s one of the most important things in a tree. If you compare trees to housing construction, the lignin is the cement. Lignin is found in and between the cells in wood. It keeps the cells from collapsing – that’s how trees grow higher and higher – and helps to prevent rot. After cellulose, it’s the second most abundant organic polymer.
Extracted from the tree, there has been no doubt of the potential of lignin. But the quality is not stable so it’s difficult to have the same recipe which would be needed for consistent, high volume production. It was the fear of an oil crisis that sparked the people in our industry to pick up the pace on development and solve some of the practical issues.
At the time, phenol had our attention, as phenols are derived from oil and used widely in any number of applications including for binding agents or adhesives. The market is considerable. Lignin, being a polyaromatic network, is a suitable substitute for phenol during production of phenol-formaldehyde adhesives and it has also attracted significant attention as a renewable substitute to primarily aromatic chemical precursors currently sourced from the petrochemical industry.
Besides replacing phenol and its more traditional use as a biofuel, lignin can be used for cement to provide more credible thickening. Another application is as a replacement for bitumen (a cousin to conventional crude oil) in asphalt production for roads, roofing and some isolation materials. A little-known fact, lignin can also be used in the production of vanilla flavouring.
What’s more, lignin is a good substitute for production of carbon fibres with its high chemical resistance, stiffness and strength as well as low weight. Carbon fibres are used quite a bit in aerospace and automotive industries for components and structures, among other applications. Imagine lignin in space!
Unlocking the potential of lignin, to replace fossil-based materials, has been a focus for Stora Enso for a number of years. The Sunila Mill in Finland is the world’s first integrated lignin extraction plant to produce dry kraft lignin and fire it directly in the mill’s lime kiln and replace fossil-based fuel.
We are additionally packing lignin for sales to external customers. We use the same wood types every time, with the same level of purity and in the same processes, so we know exactly what we are getting. Same recipe, stable quality.
Suffice it to say, lignin has come to stay. Industries are catching on, research institutes and universities are concentrating more on it. At Stora Enso’s Innovation Centre in Sickla, Stockholm, we are exploring all the aspects of lignin at small and large scale – and importantly, collaborating with customers to put lignin into their reality.