Abstract
The production of algal biofuels has long-time been proven as an applicable alternative for fossil fuels. Yet, its economic performance is challenged by the inexpensive costs of fossil fuels. To address this, integrating various processes to the system yields high-value bioproducts to increase profitability and sustainability. Looking towards a circular economy perspective, the recirculation of resource flows is utilized to meet economic and environmental sustainability through the reduction of waste. Since the recovery of resources used within the production system is unpredictable in terms of output, uncertainty regarding resource recovery is assessed. Previous modelling studies have not looked into the opportunity of integrating continuous recirculation and reuse of resources along with its corresponding output uncertainty. In this work, a novel multi-objective target-oriented robust optimization model is developed centered on an algal biofuel production system that simultaneously optimizes profit and environmental impact, integrates inputs and processes aimed towards a closed-loop system, adopts the principle of resource recovery and recirculation along with the uncertainty of resource recovery outputs. A case study is solved as proof of concept and to illustrate the design methodology, optimal solutions based on economic and environmental performance are analyzed. Scenario analysis is also performed to analyze system behavior under varying conditions. Results show that to get a minimum profit, the robustness index is greater than one indicating the model is very much flexible to sudden changes in demand.
