Towards a circular nutrient economy. A novel way to analyze the circularity of nutrient flows in food systems

Recent years have seen a steep rise in the interest in nutrient circularity. In the context of food systems and waste management, nutrient circularity seems to generally encompass the reduction of nutrient losses and increased recovery of nutrients from various organic residual streams for reuse in agricultural production. Many studies that aim to contribute to improving nutrient circularity in food systems have limited the analysis to a given geographical area. But nutrient circularity likely looks different when the analysis includes what happens outside the borders of the considered area. This paper presents and discusses an analytical framework that allows for the analysis of nutrient circularity not only inside a given geographical area being considered, but also in those parts of the global food system with which the local food system interacts in terms of feed and food trade. This framework explicitly characterizes the impact of system openness associated with feed and food trade. This enables: (i) a separate discussion of four possible interpretations of nutrient circularity – internal and external input and output circularity; and (ii) an analysis of how these four circularity indicators relate to one another depending on system openness. The proposed analysis can thus reveal the extent to which a high level of nutrient circularity in the considered area comes at the cost of a decreased level of nutrient circularity in the places with which feed and food are traded, or vice versa.