Sugarcane molasses-based biorefinery: Organic acids and ethanol production

Sugarcane molasses are the largest produced waste in sugar mills; in the last harvesting cycle 2,178,131 tons were obtained and only 2.46% were used for transformation processes. Molasses has great potential to be the main feedstock in a biorefinery concept. Its composition rich in fermentable sugars and its availability are interesting features considered in this study. Through the Aspen Plus © software a multi-product biorefinery scenario was design and analyzed, technically and economically. The three main products considered were ethanol, lactic acid and succinic acid. The overall process consists of an initial stage of hydrolysis or inversion of the sucrose present in the molasses to reducing sugars followed by a specific dilution for fermentation of each of the products considered, as well as subsequent separation and purification operations. Plant efficiencies conversions were 3.24 kg of molasses/L of ethanol, 3.08 kg of molasses/kg of lactic acid and 9.25 kg of molasses/kg of succinic acid. The economic assessment was positive for organic acids production. Ethanol production had a slightly worst economic performance compared to the other processes, but the proposed scenario managed to obtain a profitability index of 1.02. The expense recovery ratio of the whole biorefinery was 1.35 which means a surplus of 35% after the project investment has paid for itself. The biorefinery’s robustness in the economic aspect comes from organic acids production; meanwhile, the social and environmental impacts are from ethanol production.