Lignin: a material to watch

More and more material companies are turning away from petrol-derived materials and turning to recycled, biobased, or waste products instead. One material that combines two of those aspects is lignin, which is showing a lot of promise when used to make various materials. Below, we discuss a few new applications in which natural lignin replaces oil-derived materials.

Lignin is a natural occurring substance in the cell walls of plants and trees, giving them rigidity. In addition to being biobased, the natural binder is actually a waste product from processes of turning biomass into paper and bioethanol.

Lignin in asphalt
In the Netherlands alone, 10 million tonnes of asphalt are produced annually, for which about 400,000 tonnes of petrol derived binder bitumen is needed, according to Wageningen University & Research (WUR) (in Dutch).

With its binding and viscoelastic properties, lignin is a suitable replacement for bitumen. In a trial, WUR produced asphalt in which 50 per cent of the bitumen was replaced by lignin. This summer, a bicycle path was constructed on campus, using various types of lignin to see which is best. Over the next few years, WUR will be monitoring how the lignin asphalt behaves itself. The outcome looks good, as there is already another trial running in another part of the Netherlands using the same material.

The main problem right now is that lignin is too expensive as raw material. In further research, WUR will look at how to make using lignin in asphalt more cost effective.

Lignin as wood glue
Finnish researchers from VTT Technical Research Centre developed a technology called CatLignin to create reactive lignin that can be used as a replacement of the toxic chemical phenol, used in wood glue. Researcher from Michigan State University (US) achieved a similar feat recently.

Phenol and formaldehyde containing adhesives are used in wood products such as plywood, laminated veneer timber and laminates.

Lignin has a 80 per cent lower carbon footprint than phenol, which also lowers the carbon footprint of engineered wood. With lignin, engineered wood can become 100 per cent biobased.

Lignin as fuel
Normally, lignin derived from bioethanol is burned and used as energy source. However, by turning it into oil, lignin can be used as a much cleaner alternative for ship fuel. A collaboration between 3 Dutch institutes – Technical University Eindhoven, Maastricht University and Maastricht University Medical Centre – called InSciTe is currently testing the product and building a trial factory, which will open in 2018.

Photos: WUR / VTT