From wood waste to nanomaterials: a patent to exploit lignin

Lignin is a component of agricultural residues derived primarily from the processing of paper and biofuels. Until recently, it was disposed of or used in applications of little value. However, lignin can now be used industrially, to produce innovative materials in a circular economy, thanks to a novel refining method patented at Ca’ Foscari.

With a European goal of climate neutrality by 2050, the recycling of waste is increasingly seen as an urgent necessity. This is a challenge that opens both new frontiers in materials science and opportunities for business. Even though lignin accounts for 30% of lignocellulosic materials – it is a residue from biofuel production (half a kilogram of lignin for every liter of biofuel!) and agro-industrial manufacturing (not only paper, but also jams, tomatoes, beers) – so far it has not found viable applications. The research group at Ca’ Foscari, led by Claudia Crestini, has discovered and patented a method that transforms lignin into a commodity based on high value-added materials. The method can be used on an industrial scale. 

"We try to develop sustainable production processes from natural biomass", explains Professor Crestini, who came to Ca' Foscari in 2019 with the research group, "PPM - Natural Polyphenols Chemistry & Material Science Laboratory". Lignin has been at the center of her research since the early 1990s, when the words "circular economy" were not yet fashionable. During the past year, interest in this natural polymer has grown exponentially abroad because of its great potential and thanks to the development of new fractionation and refining techniques which hitherto were available only on a laboratory scale. Professor Crestini's research team has now finalized a larger scale method for industrial plants to integrate into line activities of waste producers (such as paper mills) or new plants specialized in extraction.

This new process is called segmented flow fractionation. It consists of refining (extracting) the lignin fractions with a priori-defined and -reproducible characteristics (i.e. similar molecular weight range and chemical-physical characteristics) from the residues of any origin, using "green" and recyclable solvents. Continuous cycle fractionation is extremely flexible and can be modulated according to the type of product to be obtained. 

Professor Crestini explains: "Obtaining a high quality refined material with defined, modular and constant structural characteristics at an industrial level opens the way for its use in the development of an infinite number of materials, such as: plastics and composite materials for consumer care, household cleaning; nanoparticles for the controlled release of active ingredients in cosmetic, pharmaceutical or agricultural applications; colourless nanofibres (even though lignins are almost black in origin); or nanocomposite reinforcing agents (resins with antimicrobial and sunscreen properties, carbon nanofibres,...). It is an environmental challenge which could bring an economic advantage once a target market is created. For this reason, our research team is also working on new materials in which to exploit this high-quality lignin fraction, thus enhancing the entire cycle of use, recycling and biodegradation of wood and lignocellulosic materials". 

A new intermediate market of a lignin refining chain could also be developed.  A host of companies would benefit from this: from large multinational paper mills in northern Europe to small and medium sized agri-food companies locally. This potential augments the immediate applications of lignin described here and more in depth in PPM’s research materials. Ca’ Foscari, through its Knowledge transfer office - PInK, is ready to facilitate contact and discussion between Professor Crestini’s research group and the private sector in exploring how lignin can be utilized in an industrial and commercial manner. 

The team, composed by Prof. Crestini and Ca’ Foscari researchers Dr. Matteo Gigli, Simone Cailotto and Nicolò Pajer, who work in close collaboration with Dr. Heiko Lange of the University of Naples Federico II and Prof. D. S. Argyropoulos of North Carolina State University (USA), has also developed innovative lignin analysis and characterization techniques, recently published in Nature Protocols; they and are now participating in European calls in which they intend to use the patented method.