Indicators and methods to assess sustainability of wastewater sludge management in the perspective of two systems ecology models

Abstract

This paper, inspired by Sven Erik Jørgensen’s academic life, takes a systems ecology perspective on sustainability in wastewater sludge management. First, an overview identifies the indicators and methods currently used to assess sustainability and sustainable development in the area of wastewater sludge. Second, two systems ecology conceptual models are presented. Third, the indicators and methods are discussed in the perspective of these systems ecology models. Four methods were found common in assessing wastewater sludge sustainability: Life Cycle Assessment (LCA), Exergy Analysis (ExA), Emergy Analysis (EmA), and Cost Benefit Analysis (CBA). Environmental Risk Assessment (ERA) was added since it was found to be used in the larger wastewater treatment context, and complements the other four methods. When comparing the indicators and methods with the systems ecology models it was found that no method covered every aspect of the models. ExA, EmA and ERA covered the full extent of the models but not from every aspect interesting from a sustainability point of view. LCA and CBA had a lower reach at the ecosystem side of the models, but produced deeper knowledge regarding environmental impacts for LCA, and economic flows and storages for CBA. The investigation concludes that a complementary approach of methods and indicators is needed to assess sustainability, and they are suggested to be used in an integrated way, in the spirit of Sven Erik Jørgensen’s findings.