Whole sweet sorghum plant as a promising feedstock for biobutanol production via biorefinery approaches: Techno-economic analysis

Sweet sorghum plant, containing starchy grain, juice, and bagasse, is a potential energy crop for biobutanol production as an advanced renewable fuel. This paper assesses the economy of production of butanol from the whole sweet sorghum plant based on available experimental results. Different scenarios, including separate hydrolysis and fermentation (scenarios 1 and 2), simultaneous saccharification and fermentation (scenario 3), and co-fermentation of the juice and pretreated stalk (scenario 4), were simulated using Aspen Plus®. Moreover, in scenarios 5 and 6, the stalk is directly fed to the fermenters without juice extraction and pretreatment. Gas stripping was used to enhance the recovery and fermentation yield in scenarios 2 to 6. Acetone, supplied from the process products, was used for bagasse pretreatment in scenarios 1–4. Economic viability was investigated using Aspen Process Economic Analyzer. The butanol production price was 0.62, 0.44, 0.45, 0.61, 0.39, and 0.56 US$/L for scenarios 1 to 6, respectively. The most profitable process was scenario 5, where US$47.75 million total capital is required for the production of 11,260 tonne/year butanol. The sensitivity analysis of butanol sales price showed that even in the case of its value reduction by 50%, scenario 5 can still be profitable.