It is becoming important to understand the lignin structure and properties to provide key features and insights for better/efficient lignin valorisation strategies. Technically speaking, the lignin surface properties are affected by the biomass substrate source and the pretreatment process conditions. In this sense, the physicochemical characterisation of different industrial (technical) lignins are performed exploiting different methods, like Brunauer–Emmett–Teller N2 adsorption, particle size distribution, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, gel permeation chromatography, and thermogravimetric analysis. The measured physicochemical properties will help in proposing potential valorisation routes for these lignin streams within the project scope, focusing on their depolymerisation and subsequent biological conversion to value-added chemicals and fuels.

Green solvents are screened for their ability to solubilise and extract technical lignin streams and different solvents mixtures are selected/designed in accordance towards selective/efficient lignin fractionation methodologies. The elucidation of such lignin fractions properties is crucial in the direction of understanding its complex molecular structure, boosting its homogeneity, and fostering technologies for advanced lignin-based materials.

Lignins from different sources are depolymerised through different catalytic approaches with the aim of producing low-molecular-mass aromatics that may participate in various microorganisms’ metabolisms as well as in other fuels/energy sector applications. The tests are performed using a tailored continuous flow reactor (CFR) system and new regimes/conditions for such reaction are investigated. Product separation and upgrading tasks are also conducted and evaluated using different characterisation techniques, such as SEC, NMR, and SFC-MS. 

Purification of depolymerised lignins is essential for the application in some products like fuels and fine chemicals. It is crucial to remove salts that are present in high concentrations in some lignin samples. This is accomplished by a purification method including ion exchange and anti-solvents. Understanding the properties of the lignins increases the possibility to optimize the purification process.