Assessing nitrogen circularity in food systems in the North China Plain

Enhancing nitrogen (N) circularity is crucial to mitigate the environmental impacts of N losses in food systems. Substance flow analysis (SFA) effectively assesses N flows, but its application to evaluating food system circularity in China remains limited. We used a SFA model of food system with detailed representation of animals and waste in the North China Plain, an agricultural-intensive area, to assess eight circularity indicators. Findings revealed that the area imported 49 % of feed N yet maintained food N self-sufficiency by producing 110 % of consumed food N. Nitrogen Use Efficiency was 19 %, with 56 % of waste N recycled, contributing half and one-third of fertilizer and feed N inputs. Furthermore, circularity performance varied among prefecture-level cities, with better outcomes in agriculturally active, less populated, and less urbanized areas. We illustrate SFA's value in assessing circularity in Chinese food systems while advocating for improved model accuracy and complementary indicators, emphasizing tailored strategies.