Minimizing the environmental impacts of waste valorization systems using multi-criteria life cycle optimization

Unsustainable waste management practices impose severe environmental hazards, health risks, and financial burdens. Waste valorization systems have emerged to mitigate the negative impacts of landfilling while recovering finite materials and renewable energy. This study aims to develop a life cycle assessment (LCA)-based multi-criteria framework using linear programming to optimize municipal waste allocation to multiple valorization facilities. The developed optimization model minimizes the life cycle impacts of integrated waste management on several life cycle impact categories. A multi-criteria decision-making analysis is implemented to account for the relative importance of the examined environmental categories, and a sensitivity analysis is conducted to study the effect of varying the importance weights. The variation between different LCA methods, IMPACT, CML, and ReCiPe, is also investigated. The proposed framework is applied to Egypt based on local conditions and strategic priorities. The LCA findings reveal that processing recyclables in material recovery facilities enhances the environmental performance in all impact categories except ozone layer depletion. To achieve minimum environmental effects on the assessed impact categories, single objective models suggest the diversion of recyclables to material recovery facilities and non-recyclables to gasifiers. The Pareto front of IMPACT involves anaerobic digesters and incinerators, CML comprises composting facilities, and ReCiPe includes incinerators. Overall, this study provides a lifecycle-based decision-making guide for the planning and optimization of sustainable waste management systems, and highlights the potential variations in the outcomes of different LCA methods adopted.