Rethinking circularity with Re-refineries and supply chains reintegration via multi-objective pareto graph theoretical approach

Amidst the global effort in energy transition from fossil fuel remains a challenge for the heavily dependent oil and gas (O & G) industry. Thus, the circular economy (CE) concept offers a viable approach to improve the longterm sustainability of the O & G industry while transitioning toward sustainable development. This research proposed the re-refinery strategies to attain circularity within the O & G industry. Two models are developed to address the strategy decision on both Meso (re-refinery technology decision optimization via P-graph approach) and Macro (supply chain optimization via mixed-integer linear programming (MILP)) perspectives. The re refining of waste oil utilizing membrane ultrafiltration followed by hydrofinishing is favoured in both cases for its economic potential contributed by its higher production yield (89.94 wt%) compared to distillation (77.12 wt%) pathway. Overall, the re-refining strategy suggest promising improvement in both economic (27.17% lower cost) and environmental (55.35% lower emissions) performance. The addition of in-situ lubricant blending incurred a 4.49% reduction in total cost of the supply chain as compared to the base case with primary reduction (31.48%) in transportation. This study reveals the potential of re-refining approach which serves as guidelines for decision-makers and researchers to strengthen CE practice in modern O & G industry.