Evaluation of different sweet sorghum cultivars for bioethanol yield potential and bagasse combustion characteristics in a semiarid Mediterranean environment

Abstract

Sweet sorghum is a promising bioenergy crop that has great potential for bioethanol production due to its wide adaptability, high sugar yield, and drought tolerance. The objective of the present study was to evaluate the bioethanol yield potential and bagasse combustion characteristics of 13 sweet sorghum cultivars in a semiarid Mediterranean environment. The results showed that M81-E was the most promising cultivar for whole-crop bioethanol production due to it having the highest total ethanol yield, at 6885 L ha−1. Dale exhibited the highest juice ethanol yield (1764 L ha−1), with the lowest lignin (8.9%) and ash (2.31%) contents. The bagasse moisture contents of the cultivars were quite high, which varied between 66.61% and 70.51%, indicating that the bagasse must be dried before it is used as a feedstock for direct combustion. In this context, M81-E and Top76-6 were less suitable for solid biofuel production from their bagasse, because their comparatively long growth cycle did not allow for the open-air drying that was required to decrease the moisture content to an optimal level at a low cost. On the other hand, Umbrella was a promising cultivar in the study, because it achieved the highest dry bagasse yield (16.5 t ha−1) and a total ethanol yield (6350 L ha−1) comparable to that of Dale. These results suggested that sweet sorghum had a high potential for bioethanol production in a semiarid Mediterranean environment, but cultivation of the most suitable cultivars is the first step to ensure sustainability.