From waste biomass to bio-fuel: an innovative and sustainable approach to ethyl levulinate production

Environmental issues related to fossil fuel use are driving research toward sustainable alternatives, with biomass emerging as a key source of chemicals and biofuels. Notably, significant attention is paid to the use of waste biomass from industrial and agricultural sectors as starting raw materials. This approach not only leverages a low-cost and abundant resource for energy production but also contributes to reduce the negative environmental impact. Among the valuable products derived from biomass, ethyl levulinate (EL) represent an outstanding and strategic bio-product which can be directly obtained from the direct acid-catalysed alcoholysis of biomass C6 polysaccharide fraction. Specifically, EL is considered a promising bio-blendstock that can be used in both diesel and gasoline engines, but also a strategic intermediate for the obtainment of value-added products. Preliminary, this work focused on the valorisation of thick juice (TJ), a viscous aqueous solution rich in sucrose that is largely produced from the sugar refinery. The optimisation of sucrose ethanolysis, adopting ethanol as a green reagent/reaction medium and H2SO4 as cheap homogeneous catalyst, was studied as model reaction allowing to identify the optimal conditions for EL formation, resulting in a 54.6 mol% yield. These conditions were subsequently applied to TJ conversion, allowing to reach an EL yield of about 38 mol%. Finally, the study shifted to the valorization of bread waste (BW), a major contributor to the global food waste stream. Due to the high starch content, BW appears as an excellent low-cost raw material for producing EL. Thus, the ethanolysis of BW was investigated using a One-Factor-at-a-Time (OFAT) approach, allowing EL yield of ~40 mol%. Lastly, EL was evaluated as bio-blendstock in a gasoline internal combustion engine, resulting an excellent bio-additive when blended up to 20 vol%. In conclusion, this study presents an innovative approach for the sustainable production of EL through the valorization of BW or TJ, followed by its evaluation as a bio-blender for gasoline.