Leveraging circular nutrients to improve the sustainability of peri-urban agriculture

Agriculture in the urban periphery (peri-UA) can potentially reduce its environmental impact through nutrient recovery from municipal solid and water waste, promoting local crops and displacing some dependency on imports. Shifting from linear to circular food-supply strategies should systemically consider trade-offs that depend on city-specific factors, such as crop patterns, waste management capabilities, and ecosystem status. We investigate these effects spatially and temporally with a tool based on prospective regionalized life cycle assessment to determine how the local and transboundary impacts of various strategies of nutrient circularity (such as struvite, compost, and recovered ammonium salts) applied to peri-UA areas affect climate change, regionalized marine and freshwater eutrophication, abiotic resource depletion, and water consumption, providing maps reflecting crop yields and impacts to aid urban planners. We illustrate with the Metropolitan Area of Barcelona, where we find that applying compost with current waste management infrastructure can reduce the carbon footprint of peri-UA areas by up to 85%.