Valorization of Mixed Food Waste for Bioethanol Production: Process Simulation and Optimization

Mixed food waste represents a realistic yet highly heterogeneous feedstock for bioethanol production; however, most existing studies focus on homogeneous waste streams or isolated process stages such as hydrolysis, fermentation, or distillation. This fragmented approach limits a comprehensive understanding of overall system performance, particularly when feedstock variability, process selection, and energy demand are considered simultaneously. In this study, a comparative assessment of bioethanol feedstocks and pretreatment strategies is first conducted to identify mixed food waste as a representative substrate and to determine suitable conversion pathways. Building on this, an integrated process simulation and optimization framework is developed using Aspen HYSYS to model the complete bioethanol production chain, including pretreatment, enzymatic liquefaction, saccharification, fermentation, and downstream purification. The novelty of this work lies in the system-level optimization of the entire process rather than individual unit operations, combined with the implementation of heat integration and process recycling strategies to enhance overall efficiency. Optimal operating conditions were identified at 72 °C for liquefaction, 57 °C for saccharification, and 32 °C for fermentation. In the separation section, a condenser temperature of 79 °C, a separator temperature of 20 °C, and a 25-stage final distillation column enabled efficient ethanol recovery with a purity of 98.9%. Heat integration reduced total utility demand by 87.25%, while recycling streams improved resource utilization and minimized process waste. Overall, the study demonstrates that combining feedstock-level assessment with system-level optimization provides a robust, efficient, and scalable pathway for sustainable bioethanol production from heterogeneous waste resources.