Incineration of sewage sludge and recovery of residue ash as building material: A valuable option as a consequence of the COVID-19 pandemic.

Circular economy principles were adopted by European Commission, to support a sustainable growth. They contain general rules that should be considered in all situations. At present, during pandemic, some waste disposal practices are under evaluation to guarantee safety conditions. For example, in view of the recent results reporting the presence of SARS-CoV-2 virus in sewage sludge, the possibility that it diffuses in the environment is alarming. The situation may result critical in densely populated cities, which are the largest sources of sewage sludge. In this frame the diffused practice of reuse of this waste in agriculture is under revision. In this context, incineration may represent a valuable alternative strategy to manage sewage sludge during pandemic. Indeed, due to thermal treatment, the destruction of organic micropollutants and pathogens, eventually present in the waste, is guarantee. Moreover, it is fundamental to highlight that also if the management of sewage sludge changes, the ash resulting from its combustion may have suitable reuse opportunities, and their landfilling should be avoided. This work presents the available possibilities of sewage sludge ash recovery in building applications and shows the results obtained by the analysis of their sustainability. The approach is based on the use of embodied energy and carbon footprint values, to make a simple and fast new method able to be a suitable tool to support and promote sustainability also in critical situations (such as pandemic) and when all the information about a technology are not available, making not possible to perform a full-LCA approach. This work aims to be not only a reference paper for promotion of strategies able to increase waste management safety, but also an example showing that circular economy principles should be pursued also if boundary conditions can change.