A Bibliometric perspective on the evolution of research in sludge management: Opportunities and challenges

Conventionally regarded as a liability, sewage sludge (SS) continues to accumulate due to rapid industrialisation and global population growth. However, the conversion of SS into energy and nutrients presents a promising alternative for sustainable waste management. Drawing from the Web of Science database and using VOSviewer for bibliometric mapping, this review investigates the research trends, intellectual structure, and collaborative networks in sludge management over the past decade. It further evaluates the strengths, particularly in alignment with the Sustainable Development Goals (SDGs), as well as the weaknesses, opportunities, and threats associated with current sludge management practices. The analysis reveals that key emerging research themes include microbial diversity in activated sludge, biological treatment processes and their limitations, and thermochemical conversion for energy and nutrient recovery. Future research is encouraged to focus on innovative remediation approaches for emerging contaminants and microplastics, and the development of scalable technologies for the commercial production of energy, nutrients, and value-added chemical products from SS. This study offers a comprehensive overview of the evolution of sludge management research and provides critical insights to inform policy direction, investment priorities, and academic engagement. It also advocates for increased financial support, stakeholder incentives, and collaborative partnerships, noting that substantial progress toward achieving multiple SDGs can be made through strategic investment in sludge management initiatives.