Thanks to the naturally-occurring substance lignin, we will be able to reduce our future use of oil and coal. The substance can be obtained using an acclaimed Swedish technology that not only extracts lignin but also enables paper mills to increase productivity.
Despite being generally regarded as a waste product, lignin has the potential to replace both oil and coal and can be used in a wide range of products. The Swedish separation process LignoBoost means that lignin can instead be viewed as a valuable and functional resource.
The lignin extraction technique was developed by researchers from RISE and Chalmers as early as the 1990s and is today owned by Valmet, which has installed the technology in three paper mills. Lignin is extracted from black liquor, a byproduct of boiling during pulp manufacture. Cellulose is the component of wood used for pulp while lignin is separated into black liquor, which is later burnt for energy.
“There is a limit to the amount of lye that the recovery boiler can accommodate and incinerate. This makes the recovery boiler a limiting factor for increasing a paper mill’s capacity. From this viewpoint, one could say that the recovery boiler controls pulp production at the mill,” explains Katarina Ohlsson, who leads the Lignin unit at RISE.
Increased capacity the driving force behind lignin extraction
This problem is however surmountable and it was just such a solution that was the initial driving force behind LignoBoost. In brief, LignoBoost involves leading a certain percentage of the black liquor away to a precipitation unit instead of incinerating it in the recovery boiler.
“In this unit, carbon dioxide is added to precipitate and filter out lignin. which is then washed in the next step. This relieves the recovery boiler and increases the production of pulp to an extent dependent on the situation at the individual mill, while simultaneously extracting valuable lignin with a high level of purity,” explains Katarina Ohlsson.
Many areas of application
So, the separation process is well-established and RISE researchers are currently working primarily to make the extraction of lignin more efficient, as well as to develop new applications for the lignin produced.
There are a wide variety of applications for this bio-based material, such as in bio-based plastics. Many of today's plastics are still made from crude oil. If this production can be changed to a bio-based raw material such as lignin, it would have a positive environmental impact.
Lignin can also be used in many other products; glue, coatings, asphalt, batteries and composite materials for the automotive industry to name but a few.
“There is enormous potential in battery research and it is important to continue research and development work and identify areas of application for lignin. Those of us working on LignoBoost place a great deal of emphasis on ensuring that lignin produced by the technique is used and provides benefits!”
Facts: Lignin
Lignin is a polymer and one of the three main components of wood. Lignin binds the cellulose fibres in the wood, as well as strengthening the tree trunk. Generally speaking, lignin is not required in the manufacture of paper and so it is separated in the pulp process and treated as waste. Most lignin is incinerated as an energy source for the paper mill; however, it is far more than simply a byproduct and can be used as a replacement for oil and coal and in materials such as carbon fibre. Lignin can even be used to produce nature-identical vanilla for use in pastries and ice cream – a cheaper alternative to obtaining vanilla from vanilla orchids.
