The biorefinery approach for large-scale biomass utilization involving the co-production of bioethanol and value-added products has received a great deal of attention. A techno-economic evaluation of an innovative integrated biorefinery approach using macroalgae cellulosic residue (MCR) was investigated in the present study for the co-production of bioethanol and L-lactic acid (LLA) via Aspen Plus V10. The simulation resulted in a production capacity capable of producing 3856.8 kg/hr of anhydrous bioethanol, 6488.04 kg/hr of LLA, 4479.48 kg/hr of fertilizer, and 5233.79 kWh of electricity generation from a feedstock of 15883.3 kg/hr of MCR. The yield of products per unit mass of feedstock were 0.24 kg of anhydrous ethanol, 0.41 kg of LLA and 0.28 kg of fertilizer per kg of MCR. The bioethanol product has a purity of 99.7 wt, while the product purity of LLA is 92.8 wt. The electricity generated from the combined heat and power (CHP) plant managed to supply up to 70 of the plant's total electricity requirement. The implementation of Heat Exchanger Network (HEN) synthesis successfully generated a total energy savings of 35 through the optimization process. With a plant service year of 20 years, the payback period is 6.25 years, having a Return on investment (ROI) of 30.8. Furthermore, the plant is equipped with futuristics integration of Industry 5.0, implementing the effort of human-robot interaction to achieve maximum efficiency and productivity. © 2021 Elsevier Ltd