Evaluation of Different Sweet Sorghum Cultivars for Sugar Characterization and Theoretical Bioethanol Yield in a Semi-Arid Sub-Saharan Environment

Abstract

Growing demand for sustainable energy has increased attention toward non-food feedstocks for bioethanol production that places pressure on food resources. Sweet sorghum (Sorghum bicolor (L.) Moench) is increasingly considered as an alternative bioethanol feedstock due to its favourable agronomic and sugar-yield characteristics, such as its short growing cycle, high sugar content, drought resistance, and adaptability to marginal lands, as well as its ability to drastically reduce the ‘food versus fuel’ crisis. Despite global advances and although Nigeria ranks among the world’s leading sorghum-producing countries, the use of sweet sorghum for bioenergy applications remains limited. This study evaluated thirteen sweet sorghum cultivars grown under rainfed conditions in Kano, Nigeria, a semi-arid environment in sub-Saharan Africa during the rainy season between June and October 2023. A randomized block design (RBD) consisting of three replications were used. Sugar characterization parameters such as °Brix content, sugar content, and fermentable sugar concentration were determined. Theoretical bioethanol yield was calculated using a glucose-to-ethanol conversion factor. Results revealed significant varietal differences in the sugar characterization parameters as well as theoretical bioethanol yield. Among the cultivars, SAMSORG 50 SW and Sugar Drip recorded the highest theoretical bioethanol yield values of 98.1 g/L and 95.0 g/L, respectively, indicating their strong potential for bioethanol production in Nigeria’s dryland zones. The findings demonstrated the prospects of utilizing sweet sorghum for bioethanol production in semi-arid Nigerian environment and provided a basis for selecting cultivars for subsequent field-scale evaluation.