Marginal Abatement Cost Analysis of Wastewater Reuse Systems under Varying Renewable Energy Penetration and Operational Conditions

This study evaluates the environmental and economic performance of a wastewater reuse system (MBR + UF/RO) in Jeju under varying levels of variable renewable energy (VRE) utilization. Hourly-resolution data (8,760 hours) on electricity generation mix and wastewater treatment operation were used to conduct dynamic life cycle assessment (dLCA) and techno-economic assessment (TEA). Under a PPA-based electricity procurement framework, nine scenarios were analyzed by combining renewable energy penetration levels (0-80%) with two operational strategies: WWTP-coupled (F1) and VRE-following (F2). The results show that increasing renewable energy penetration reduces GHG emission intensity by up to approximately 70% per unit of reuse water. The marginal abatement cost (MAC) ranges from 34 to 41 thousand KRW/tCO2eq and exhibits a non-linear pattern, peaking at 40% penetration before declining at higher levels. In addition, the F1 strategy consistently achieves higher emission reductions and lower MAC compared to F2. These findings highlight the importance of temporal alignment between electricity procurement and operational strategies and emphasize the need for MAC-based decision-making in decarbonizing public infrastructure systems.