Portugal is deficient in phosphate fertilizers. However, it also hasa phosphorus (P) consumption chain with potential to promote sustainable management of P from waste. Creating a link between the waste and agricultural sectors supports a reduction in external dependence and promotes the circularity of a secondary raw material.
Gathering information about productive quantities, pollutant discharge points (PDPs), and P concentration in industrial activities, it is possible to infer the following: the food industry is concentrated in coastal urban areas like Lisbon and Porto, but contributes minimally to P losses in the form of waste (383 t/year); wastes from slaughterhouses, while rich in protein and suitable for biogas production, only contribute minimally to P resources (82 t/year); urban solid waste management is more structured, although with efforts in recycling and biogas production, its role in P recovery remains modest (1,35 kt/year); urban wastewater, however, shows the greatest potential for P recovery due to its widespread geographic distribution, and nutrient-rich sludge (7.3 kt of P). This highlights opportunities for P management, enhancing biofertilizer production.
Using the concept of Regional Resilience (RR) and Territorial Metabolism (TM), this work estimated agricultural demand for P fertilizer in mainland Portugal and P content in sewage sludge, from urban wastewaters, to partially replace the use of inorganic P fertilizers, at the municipal level. So far, Lisbon Metropolitan region appears to have the potential to reach 2,631.87 t/year of P recovered from wastewater, surpassing local agricultural demand (126.83 t/year). In the northern region, sewage sludge contains enough P to meet 25% of the region's fertilizer needs. In the Centro Litoral region, it is possible to meet 48% of the corresponding P needs. Opportunities for implementing synergy require accurate information on infrastructures, technology assessments corresponding to local characteristics, economic and environmental contributions, and compliance with legislative targets.
