Phosphate recovery from exhausted extinguishing powders: A case study of circular economy in the chemical industry

Nowadays in Europe, an exhausted extinguishing powders (EEP) industrial recovering process is still missing, fertilizer demand is increasing, phosphorous is a critical raw material. In this perspective, an EEP treatment pilot plant was realized, allowing the recovery of a high-value, non-renewable raw material, phosphate, transformed into fertilizers. This case study offers an example of circular economy and industrial symbiosis in the chemical industry (EEP are valorised as secondary raw materials in another sector, otherwise disposed of as special waste and not recovered) and highlights how to tackle with chemical processes using waste as secondary raw material. The boundaries choice between first and second life and on how to assess processes comparative analyses are the main critical points to deal with. The innovative PHOSave process is based on a mechanical treatment, a washing phase with an aprotic solvent and a biological treatment. To evaluate its environmental feasibility an LCA study was performed at the design stage. The scenario considered is from cradle-to-gate, from the collected EEP to the micro-fertilizer produced. Life cycle impact assessment of the innovative PHOSave process, using the CML impact method, has demonstrated that solvent choice for the washing phase has a huge influence on the overall environmental performance; in any case, the highest burden comes from the granulation phase.