Efficient Bioethanol Production from Yam Peel Waste via Acid Hydrolysis and Fermentation

Food residues can be transformed into bioethanol, reducing CO<sub>2</sub> and methane emissions while fostering sustainable development. This method provides a cost-effective way to enhance the value of non-edible food sources. Thus, yam peels produced as agro-industrial waste is perfect starting material for bioethanol production. The main goal of this study is to evaluate the efficiency of bioethanol production from yam peels. Thus, fresh peels are subjected to wet milling to obtain a starch-rich powder. The hydrolysis of dry extracts, optimized according to time, acid concentration, and dry extract (DE)/water volume ratio, is carried out by reflux heating in the presence of different concentrations of H<sub>2</sub>SO<sub>4</sub> used as a catalyst. The ethanolic fermentation of the hydrolysate musts, after adjusting the pH to 4.5, is conducted in batch mode using <i>Saccharomyces cerevisiae</i>. Fermentation monitoring is ensured by measuring °Brix with an Abbe refractometer, while the ethanol content is determined by the pycnometric method, in accordance with the recommendations of the Association of Official Analytical Chemists (AOAC). According to the results obtained, the optimal hydrolysis conditions include: an H<sub>2</sub>SO<sub>4</sub> concentration of 8% (w/w), a dry extract (DE)/water volume ratio of 1:5 (g/mL), and a duration of 2 hours. These conditions yield an ethanol content of 6.72 ± 0.26% (v/v), corresponding to 264.97 ± 10.07 g EtOH/kg of dry matter. Wet milling provides better ethanol yields compared to dry milling. Finally, bioethanol production from yam peels prevents their degradation into CO<sub>2</sub> and methane, which are greenhouse gases. The results from this study are important for the commercial production of bioethanol through a process of valorizing plant resources and reducing waste to promote the circular economy.