DWSIM-Based Process Simulation and Exergy Analysis of Bioethanol Production from Rice Husk

Abstract

The growing concerns over fossil fuel dependency have motivated the exploration of sustainable biofuel alternatives. However, the practice of utilizing first-generation bioethanol production obtained majorly from food crops threat food supply market and poses threat to food security and land use. As a way forward, second-generation bioethanol from biomass, such as rice husk, an abundant agricultural residue, could potentially offer a promising pathway. Yet, its conversion remains energy-intensive and thermodynamically inefficient. This study aimed to evaluate the thermodynamic performance of the established process for producing fuel-grade bioethanol from rice husk. A comprehensive process model was developed in DWSIM using the Non-Random Two-Liquid (NRTL) thermodynamic framework, incorporating hydrolysis, fermentation, and distillation stages. The simulation processed 10.00 Mg of pre-treated rice husk and yielded 2.80 Mg of 99.9% pure bioethanol per hour, corresponding to a mass yield of 28.02%. Second-law thermodynamic analysis revealed an overall exergy efficiency of 79.17%, with major irreversibility occurring in the distillation column (24.54%), pre-treatment (hydrolyzer (22.05%), and fermenter (22.03%)). Through heat integration, the analysis yields a considerable energy efficiency (66.26%), and the study identifies critical hotspots for further process improvement through advanced unit operations. These findings demonstrate the feasibility of converting rice husk from waste into a valuable energy carrier, providing insights for scaling up sustainable bioethanol production and supporting circular economy initiatives.