Objective Global reliance on costly and rapidly depleting fossil fuels worsens pollution and climate change, prompting a shift toward renewable bioenergy alternatives. Bioethanol offers a sustainable alternative that reduces fossil-fuel dependence and diversifies energy sources. Methods The present study investigated bioethanol production from guava waste juice supplemented with sorghum, using fermentation and distillation, offering a sustainable solution to competition with food supply and management of municipal solid waste. Supplementation with sorghum flour enhances the hydrolysis of complex sugars in guava fruit waste juice and improves fermentation efficiency after which the fermented juice broth was distilled at 78 °C to produce bioethanol. Results Total soluble solids (TSS) decreased throughout the fermentation period with a more pronounced reduction observed in the broth supplemented with sorghum. The mean TSS values for broths with and without sorghum supplementation were 2.443 ± 1.572 and 2.981 ± 1.817 °Brix, respectively, with the difference being statistically significant (p = 0.001). The sorghum-supplemented broth produced the higher alcohol content of 7.87% ABV than un-supplemented broth which gave 6.56% ABV as determined from specific gravity measurements before distillation. Distillation yielded 22%, 18%, and 12% alcohol content in the first three 100 mL aliquots with sorghum compared to 19%, 14%, and 9% without sorghum. Redistillation increased bioethanol purity from 9-22% to 50-84%, suitable grade for intermediate fuel, solvent, or a feedstock for other value-added bioproducts. Conclusion Overall, the study demonstrates the potential of guava fruit waste, complemented with sorghum as a sustainable feedstock for bioethanol production. This exploratory study shows that sorghum can enhance bioethanol yield and quality, while highlighting opportunities for process optimization and scale-up to support circular-economy and waste-to-energy initiatives.
Mtashobya et al. (Wed,) studied this question.