Making waves: Multicriteria strategies are key to reimagine the future of sewage sludge processing in Europe

Sewage sludge management in Europe needs to be thoroughly rethought. While concerns about hazardous contaminants increasingly drive interest in thermochemical sludge treatments, this approach risks causing considerable losses of organic matter and nutrients, key components to be recovered, considering the urgent need to restore degraded soils in some European areas. In fact, there is no single technology capable of simultaneously optimizing risk minimization and resource recovery. This perspective calls for a rethinking of sludge management, from a single technology solution approach to multicriteria strategies that can find a compromise between risk and valorization according to context-specific conditions. Multicriteria approaches, considering physicochemical, agronomical, environmental, economic and social dimensions, offer a more realistic basis for sustainable choices. To enable this, Europe needs harmonized data, standardized measurement protocols and shared statistical tools leading to a "sludge passport" that integrates key information on composition, quality and ecotoxicological risks. Emerging integrated and modular process configurations, such as the coupling of biological and thermochemical treatments, offer a vision of how multiple goals can be reconciled. The path forward is not about identifying a single "best" option, but about building flexible strategies that align sludge management with Europe's soil health and circular economy goals.