Phosphorus recovery from sewage sludge ash: life cycle inventory and critical review of LCA case studies

This study addresses critical issues in the life cycle assessment (LCA) of phosphorus (P) recovery from sewage sludge ash (SSA). One of the main related challenges is the lack of robust and reliable data inventory. Additionally, the systems for P recovery from SSA are complex and multifunctional, leading to inconsistencies and contradictions in the literature regarding LCA modeling assumptions and results. To tackle these challenges, existing P recovery technologies from SSA are reviewed. A comprehensive analysis of each technology's material and energy flows is conducted based on literature reviews, providing a valuable data source for future LCA-based investigations. Finally, a review of 18 LCA studies on P recovery technologies from SSA is presented, detailing methods for scenario definition, choice of functional unit, handling of multifunctionality, and findings. Different LCA modeling assumptions have been used in the literature to estimate the environmental burden of P recovery from SSA. These include various methods of considering the system function, defining functional unit, and solving multifunctionality. Additionally, studies employ diverse impact categories and assessment methods, leading to differing and incomparable conclusions. So, a set of recommendations is provided to standardize the approaches of LCA studies on P recovery technologies and ensure comparability of results.