Life cycle energy and GHG emission within the Turin metropolitan area urban water cycle

The aim of this study is to analyze the urban water cycle in the Turin Metropolitan Area (Northwestern Italy), with a focus on quantifying the annual life cycle energy consumption and greenhouse gas emissions. The study made use Material Flow Analysis and Life Cycle Assessment methods for a defined urban water cycle system (ATO3) operated by one water utility (SMAT S.p.A.), and examines all main sub-systems of the entire urban water cycle. The study quantified the annual direct and indirect energy consumption and the direct and indirect greenhouse gas emissions related to system-wide energy consumption and the production and transportation of chemicals used in water treatment and wastewater treatment plants. It is found that the wastewater treatment consumes the biggest share of the total energy (44%), but a significant part of this energy demand is provided by the energy in biogas produced from wastewater sludge. On the basis of this study it was possible to provide strategic recommendations to the water utility on how to improve the water/energy/carbon nexus and contribute better to sustainability performance of urban water cycle systems.