Conclusion
Economic aspects of sewage sludge management

Sewage sludge management lies at the heart of the transition to a circular economy and can no longer be viewed strictly from a technical or accounting perspective. The sum of internal costs and environmental and health externalities requires aligning the private optimum with the social optimum through economic instruments (Pigouvian taxes, fees, permits, subsidies, Extended Producer Responsibility) and a strengthened regulatory framework (land application standards, traceability, quaternary treatment, revision of the European directive).

Sustainable solutions combine technological innovation, process optimization, resource circularity, and shared governance. Best practices (nutrient and energy recovery, advanced wastewater treatment, reduction at the source, and pooling of resources) are technically and economically viable if the mechanisms are properly calibrated...