Sustainable Wastewater Sludge Valorization: A Critical Review of Life Cycle Assessment and Techno-Economic Studies

Rapid population growth has led to increasing quantities of wastewater treatment sludge, creating environmental, economic, and public health challenges that require sustainable management strategies. This review critically examines recent advances in wastewater sludge management by evaluating sludge characterization, conventional and emerging valorization technologies, and the application of life cycle assessment (LCA) as a decision-support tool. The analysis shows that sludge can be successfully valorized through agricultural reuse, energy recovery, industrial applications, and resource recovery. However, the suitability of each pathway depends on sludge properties, environmental conditions, regulatory requirements, and economic feasibility. LCA highlights the environmental trade-offs associated with different management scenarios and provides a systematic framework for comparing their environmental and economic performance while supporting circular economy principles. Overall, integrating sludge valorization with comprehensive life cycle assessment enables more informed decision-making and promotes environmentally sustainable and economically viable wastewater sludge management. This review provides practical insights for researchers, policymakers, and industry stakeholders seeking to optimize sludge management strategies and advance sustainable wastewater treatment.