AGRICULTURAL WASTES VALORIZATION TO OBTAIN NEW COMPOUNDS AND CHEMICAL BUILDING BLOCKS

THE TRANSITION TOWARD A CIRCULAR BIO-BASED ECONOMY REQUIRES THE DEVELOPMENT OF SUSTAINABLE STRATEGIES FOR THE EFFICIENT VALORIZATION OF RENEWABLE RESOURCES, PARTICULARLY UNDERUTILIZED AGRICULTURAL RESIDUES. AMONG THESE, THE RESIDUAL WASTE FROM LIGNOCELLULOSIC TREE PRUNING GENERATED ANNUALLY IN MEDITERRANEAN AGROFORESTRY SYSTEMS REPRESENTS AN ABUNDANT, LOW-COST, AND NON-FOOD-COMPETING BIOMASS RESOURCE WITH SIGNIFICANT POTENTIAL FOR CONVERSION INTO VALUE-ADDED PRODUCTS. THIS DOCTORAL RESEARCH FOCUSES ON THE INTEGRATED VALORIZATION OF OLIVE AND HAZELNUT TREE PRUNING RESIDUES THROUGH TAILORED PRETREATMENT, FRACTIONATION, AND DOWNSTREAM CONVERSION PATHWAYS, AIMING TO PRODUCE FUNCTIONAL LIGNIN, FERMENTABLE SUGARS, AND BIO-BASED MATERIALS ALIGNED WITH EUROPEAN SUSTAINABILITY POLICIES. THE RESEARCH ADOPTS A DUAL METHODOLOGICAL APPROACH CARRIED OUT IN TWO COMPLEMENTARY RESEARCH ENVIRONMENTS. IN THE FIRST PHASE, CONDUCTED IN ITALY WITHIN THE FRAMEWORK OF THE AGRITECH (PNRR) PROGRAM, ORGANOSOLV AND MICROWAVE-ASSISTED PRETREATMENT STRATEGIES WERE INVESTIGATED USING GREEN SOLVENTS SUCH AS Γ-VALEROLACTONE (GVL) AND ISOPROPANOL. THESE PROCESSES WERE OPTIMIZED TO SELECTIVELY EXTRACT HIGH-PURITY LIGNIN FRACTIONS WHILE PRESERVING STRUCTURAL INTEGRITY. DETAILED CHEMICAL AND STRUCTURAL CHARACTERIZATION OF THE LIGNINS AND ISOLATED AROMATIC STRUCTURES WAS PERFORMED USING SPECTROSCOPIC TECHNIQUES (1D AND 2D NMR), PROVIDING INSIGHT INTO LIGNIN ARCHITECTURE, MONOLIGNOL COMPOSITION, AND FUNCTIONAL GROUP DISTRIBUTION. THE EXTRACTED LIGNINS WERE SUBSEQUENTLY EVALUATED FOR POTENTIAL APPLICATIONS, INCLUDING ANTIMICROBIAL BEHAVIOR, ANTIOXIDANT ACTIVITY ASSESSED BY COLUBOMETRIC MEASUREMENTS TO DETERMINE ANTIOXIDANT CAPACITY (CDAC), AND ADSORPTION CAPACITY FOR HEAVY METALS IN AQUEOUS SYSTEMS. IN THE SECOND PHASE, CONDUCTED DURING A VISITING RESEARCH PERIOD IN SPAIN, THE FOCUS SHIFTED TOWARD CARBOHYDRATE VALORIZATION. ALKALINE PRETREATMENT OF OLIVE TREE PRUNING RESIDUES WAS OPTIMIZED USING A BOX-BEHNKEN EXPERIMENTAL DESIGN TO ENHANCE CELLULOSE ACCESSIBILITY AND ENZYMATIC DIGESTIBILITY. THE EFFECTIVENESS OF PRETREATMENT WAS EVALUATED THROUGH COMPOSITIONAL ANALYSIS, ENZYMATIC HYDROLYSIS, AND SIMULTANEOUS SACCHARIFICATION AND FERMENTATION (SSF), LEADING TO EFFICIENT BIOETHANOL PRODUCTION. PROCESS PARAMETERS WERE SYSTEMATICALLY OPTIMIZED TO MAXIMIZE SUGAR RELEASE AND FERMENTATION YIELDS WHILE MINIMIZING INHIBITOR FORMATION. BY COMBINING LIGNIN-FOCUSED ORGANOSOLV PROCESSES WITH CARBOHYDRATE-ORIENTED ALKALINE TREATMENTS, THE WORK HIGHLIGHTS THE FEASIBILITY OF MULTI-PRODUCT VALORIZATION FROM A SINGLE BIOMASS FEEDSTOCK. THE OUTCOMES CONTRIBUTE TO THE DEVELOPMENT OF SUSTAINABLE BIOREFINERY MODELS AND PROVIDE A SCIENTIFIC FOUNDATION FOR TRANSFORMING LOW-VALUE AGRICULTURAL WASTE INTO FUNCTIONAL MATERIALS.