Limited water and phosphorus resources and large carbon footprints of chemical fertilisers drive increased recovery of water and nutrients for reuse in agriculture. Alongside end-of-pipe technologies at conventional wastewater treatment plants, nature-based solutions provide a robust and low-energy alternative solution. This paper evaluates the potential of nature-based solutions (NBS) to close water and nutrient cycles in urban food systems, using Vienna as a case study. Applying Substance Flow Analysis, it quantifies recoverable nitrogen, phosphorus, and potassium from household wastewater and kitchen waste, modelled through treatment wetlands and biogas digesters. Results show that NBS can fully meet the nitrogen and phosphorus fertiliser demands for Vienna’s vegetable production serving 77,250 people, currently covering one-third of local consumption.
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