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 long-term 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.