Evaluation of the sustainability of technologies to recover phosphorus from sewage sludge ash based on embodied energy and CO2 footprint

This paper reports a novel and simplified approach for sustainability evaluation of new technologies, based on the use of two parameters (i.e. embodied energy and CO2 footprint) that account for the energy and emissions involved in the formation of a material, suitable to perform pre-screening analysis, preliminary to life cycle assessment. This new approach is presented and used to compare the available technologies for phosphorous recovery from sewage sludge ash. A dimensionless index, defined as SUB-RAW index, is used to compare the results about the environmental impact of each selected substituting material/process. This method is applied to full, pilot, and laboratory scale processes available in literature in the context of phosphorus extraction technologies. The results show that wet chemical leaching approaches appear to be the most sustainable methods.