Optimizing Bioethanol Yield from Papaya Rejects: A Sustainable Circular Economy Solution

The increasing generation of agricultural waste presents environmental challenges and calls for sustainable management and renewable energy solutions. This study explores the use of fruit rejects of papaya (Carica papaya) as a feedstock for bioethanol production, supporting a circular economy approach. Process optimization was conducted using response surface methodology with central composite design, varying yeast loading (2–6 tsp) and fermentation time (12–28 h). The model predicted an optimal yield of ~ 10% at 4.87 tsp yeast and 16 h fermentation time. Experimental validation produced 9.3 ± 0.76% yield, closely matching the prediction and confirming the model’s accuracy. Gas chromatography analysis showed a bioethanol concentration of 38.32% with no detectable methanol or other impurities, indicating high-quality bioethanol suitable for fuel use. The study highlights the potential of fruit rejects as a viable bioethanol source and the importance of optimizing fermentation parameters. This work contributes to sustainable fruit rejects valorization and renewable energy development.