Sewage Sludge Quality and Management for Circular Economy Opportunities in Lombardy

Abstract

From the perspective of a circular economy that prioritizes resource reuse and recovery, sewage sludge could be a source of nutrients for agricultural soils or a source of energy, depending on its characteristics. Lombardy is the region with the highest quantity of sludge production and management in Italy. A methodology was developed to: extract and analyze quantitative data on sewage sludge (EWC 190805) production and management (2017–2018); collect and analyze qualitative data from publicly available documents in tender processes for sewage sludge management (2014–2020). Sludge from Lombardy’s wastewater treatment facilities displayed average qualities that were useful for recovery in agriculture after additional stabilization treatments. Sludge showed generally low heating values and elevated water content and should require additional treatments to be used in mono-combustion. The study discovered that there is still work to be done in sludge recovery in agriculture in Lombardy, taking biosolid quality into account. Sludge, on the other hand, can be converted into energy. The methodology for collecting and analyzing site-specific data presented here can be applied to other areas. The findings can assist and guide decision-makers in developing future regional sewage sludge management strategies.