Nature-Based Units as Building Blocks for Resource Recovery Systems in Cities

Cities are producers of high quantities secondary liquid and solid streams that still poorly utilized within urban systems. In order to tackle this issue, there has been an ever-growing push for more efficient resource management waste prevention in areas, following the concept a circular economy. This review paper provides characterization flows (including water, nutrients, metals, potential energy, organics), which pass through selected nature-based solutions (NBS) supporting units (SU), expanding on study existing cases. particular, presents currently implemented NBS recovery, applicable SU dedicated increasing quality minimizing hazards specific at source level (e.g., concentrated fertilizers, disinfected recovered products). The recovery efficiency systems, where combined, operated micro- or meso-scale applied technology readiness levels higher than 5, is reviewed. importance collection transport infrastructure, treatment technology, (urban) agricultural green reuse quantity input output materials discussed, also regarding current main circularity application challenges.