Influence of Harvest Stage on Theoretical Bioethanol Yield and Bagasse Feed Quality of Sweet Sorghum Varieties

Sweet sorghum is an annual warm-season energy crop that produces high biomass, is broadly adaptable, and is tolerant of abiotic stress. This study was conducted as a two-year field experiment to determine the effects of different harvest stages (booting, 50% flowering, milk, and soft dough) on theoretical bioethanol production and bagasse feed quality in sweet sorghum varieties (Erdurmus, Gulseker, and Uzun) in the semi-humid Mediterranean transition zone. Field experiments were conducted in 2023 and 2024 using a randomized block split-plot design with three replications. In the study, characteristics such as fresh stem yield, Brix, juice yield, theoretical juice ethanol yield, dry bagasse yield, cellulose, lignin, hemicellulose, theoretical lignocellulosic ethanol yield, total theoretical ethanol yield, and bagasse feed quality (crude protein, acid detergent fiber, neutral detergent fiber, and relative feed value) were examined. According to the two-year average results, the theoretical juice ethanol yields, theoretical lignocellulosic ethanol yields, total theoretical ethanol yields, and dry bagasse yields ranged from 454.8 to 2023.9 L ha−1, 2472 to 3828 L ha−1, 3320 to 5180 L ha−1, and 7.85 to 11.67 t ha−1, respectively, in terms of the variety x harvest stage interaction. Significant differences emerged among the examined parameters across varieties. In this respect, the Erdurmus and Gulseker varieties stand out as suitable for dual use, both for bioethanol production and for bagasse utilization as animal feed. The effects of harvest stages on all examined characteristics were statistically significant. It is recommended that sweet sorghum be harvested at the latest during the milk stage to utilize the juice for bioethanol production and to evaluate the remaining bagasse as animal feed.