Microwave-Assisted Valorization of Biowastes to Levulinic Acid

The valorization of cheap and readily available biomass-based wastes such as various straws, husks, shells and peels, moreover, so far unprecedented, commercial and household wastes produced on large scale, i.e. spent coffee grounds and cooked tea leaves waste were processed as raw materials for the production of levulinic acid, a C-5-platform molecule. The results obtained by applying conventional and microwave dielectric heating at 170 degrees C were compared. It was revealed that depending on the source, the average product yields were 10-25 wt% when 2 M aqueous sulfuric acid solution was used. By applying microwave irradiation the reaction time can be significantly reduced (30 min instead of 8 h) without a decrease in product formation. The influence of the feedstock's water content on the formation of levulinic acid was investigated revealing that the drying process having significant energy needs can be eliminated from the procedure.