Invited Talk: Valorization of Food Waste into Platform Chemicals

Food waste that amounts to over one billion tonnes per year globally is a potential renewable feedstock for biorefineries. Our research focuses on the development of high-throughput catalytic systems to produce value-added platform chemicals, such as hydroxymethylfurfural (HMF) and levulinic acid, from various selected food waste that is rich in starch, cellulose, or sugars. Homogeneous (e.g., SnCl₄ and AlCl₃) and heterogeneous catalysts (e.g., zeolites) were evaluated, which carry different Brønsted acidity and Lewis acidity for controlling HMF yield and selectivity. These acidities maneuver the kinetics of desirable tandem reactions (hydrolysis of glycosidic bonds, isomerization of glucose, and dehydration of fructose) and side reactions (polymerization and rehydration). In particular, our recent studies highlight biochars functionalized via N-doping, metal impregnation, sulfonation, and acid activation as novel solid catalysts in different important reactions, for achieving sustainable and circular biorefineries. Solvents are also evidenced to play an important role beyond serving as a reaction medium, e.g., the production of HMF in the presence of acetone is substantially faster than that in dimethyl sulfoxide/H₂O and tetrahydrofuran/H₂O. Replacing the industrial co-solvent by greener alternatives, i.e., propylene carbonate and γ-valerolactone, can further accelerate the conversion of food waste. The solvent medium interacts with the substrates and catalysts, altering their reactivity during catalysis. In addition to platform chemicals, hydrochar as a potential solid fuel can be co-generated via a demonstrated microwave-assisted hydrothermal treatment of red seaweed. These research efforts elucidate the roles of different parameters in conversion systems and demonstrate a good potential of food waste valorization for the synthesis of bio-based products in real-life applications.