This research evaluates the thermodynamic performance of three polylactic acid (PLA) biorefinery scenarios, utilizing Eucheuma cottoni residue (ECR), as raw material. The thermodynamic properties of three biorefinery scenarios were obtained through Aspen Plus® V14 to conduct exergy analysis. Ultrasonic-assisted molten salt hydrates minimized the amount of ECR needed by 80.8 to produce 1000 kg/h of PLA. The fermentation unit exhibited the highest destroyed exergy in Scenarios 1 and 2, while it was the combined heat and power (CHP) unit for Scenario 3. Scenario 3, integrated with power generation and a proper waste management system, had the highest functional exergy efficiency (22.33 ). Exergoeconomic analysis was conducted after obtaining results from exergy analysis. The unit exergoeconomic cost of PLA was 188 USD/GJ in Scenario 1, while it was 187.88 USD/GJ in Scenarios 2 and 3. The unit exergoeconomic cost of electricity and fertilizer is 35.91 USD/GJ and 250.31 USD/GJ, respectively. Pretreatment and hydrolysis unit had the highest exergoeconomic factor. LA recovery unit of all biorefinery was found to have an adequate level of exergoeconomic factor. © 2024 The Author(s)