Cascade biorefinery approach to obtain hemicelluloses, lignin, cellulose and nanocelluloses from high-yield forest crops (Ulmus minor) for different industrial applications

Abstract

An Elm clone (Ulmus minor) is evaluated as a renewable lignocellulosic feedstock for a cascade biorefinery. Hemicelluloses are selectively extracted by Cold Alkaline Extraction (CAE), and the cellulose-rich residue is subsequently delignified and converted into cellulose nanofibers (CNFs). Two post-CAE treatments—alkaline hydrogen peroxide (AHP) delignification and TEMPO-mediated oxidation—are employed, and their effects on CNF physicochemical properties are assessed using FTIR, SEM, ζ-potential, conductometric titration, and thermogravimetric analysis. The combination of CAE and AHP effectively removes lignin and hemicellulose, paving the way for subsequent TEMPO oxidation to modify the fiber surface. FTIR analysis confirms the successful removal of these components, while SEM imaging reveals the structural transformations in the fibers after treatment. Techniques such as ζ-potential measurement and conductometric titration, used in conjunction, provide insight into the surface charge and degree of carboxylation, respectively. These measurements indicate enhanced dispersion stability and the effectiveness of surface modification. TGA highlights the influence of chemical pretreatment on thermal stability, with nanofibers of cellulose exhibiting distinct degradation profiles compared to untreated fibers. Collectively, these findings underscore the importance of a multi-faceted approach for optimizing the properties of cellulose nanofibers. By tailoring the pretreatment process, researchers can achieve desired characteristics for diverse applications.