Measuring the environmental impacts of sewage sludge use in agriculture in comparison with the incineration alternative

This study compares two scenarios for sewage sludge treatment i.e., agricultural-land application (LA) and incineration (INC), in an Italian context (Pavia province, Po Valley). The study was realised within a regional project aiming to obtain useful data to better address future sludge management policies. To do so, an attributional Life Cycle Assessment (LCA) approach was chosen and the multi-functionality was addressed by using system expansion. Results indicated that the scenario INC had higher impacts than scenario LA for the categories linked to process inputs and to the direct emissions of incineration, such as Global warming potential (= + 60 %)., Stratospheric Ozone Depletion, Ozone Formation, Mineral Resource Scarcity and Fossil Resource Scarcity. System expansion i.e., the production of non-renewable fertilisers, played a large role (higher impacts) in the categories related to resource scarcity in the INC scenario. On the other hand, LA scenario showed higher impacts than INC for direct emissions due to fertilisation (Marine and Freshwater Eutrophication, and Particulate Matter). In conclusion, the use of sewage sludge in agriculture seemed to be competitive with the alternative of incineration but both sludge quality and emission reduction during sludge distribution in the field play an important role in the reduction of environmental impacts.