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Abstract

Urban rooftop agriculture (RA) and photovoltaics (RPV) offer sustainable solutions for energy-23 food system nexus in cities but compete for limited rooftop space. Here we explore the potential 24 benefits (productivity, economic, and environmental) and allocation strategy of RA and RPV 25 across 13 million buildings in 124 Chinese cities, considering urban characteristics and regional 26 productivity. We found that RA yields superior economic benefits, while RPV excels in 27 greenhouse gas emission reductions. Prioritizing either RA or RPV can only retain 0–29% of 28 the above benefits brought by the other. However, allocating 61% of the flat rooftop area to RA 29 and all the remaining to RPV would retain >50% of their potential, meeting 15% (mean, 0.5 30 99% across cities) of urban vegetable needs and 5% (0.5 27% across cities) of the electricity 31 needs. While the productivity from RA and RPV have significant environmental and 32 socioeconomic benefits, they require considerable water (up to 15% of urban residential water 33 use) and materials (e.g., totaling 13 kt silver).