The environmental impacts of the scale of circularity in food systems

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CONTEXT Reconnecting nutrient cycles is essential to reduce environmental impacts of food systems. It remains unknown how circularity at different spatial scales affects nitrogen (N) losses, inputs, and greenhouse gas (GHG) emissions. OBJECTIVE We investigated impacts of reconnecting nutrient cycles in the Dutch food system at national or more local, i.e., provincial level, and assessed effects on N flows, N losses and GHG emissions. METHODS We adapted the agroecological food systems optimization model FOODSOM, by integrating soil type- and groundwater level-specific N transfer coefficients, and applied this extended model to evaluate N flows of Dutch circular food systems in a spatially explicit manner. We assessed how varying degrees of provincial food sourcing, and consequently local nutrient cycling, affected land use, N losses, and GHG emissions. The assumed diet followed national food-based dietary guidelines. RESULTS AND CONCLUSIONS Compared to the current state with substantial trade, a domestic circular food system in the Netherlands reduced land use by 26–35%, N inputs two-thirds, NH 3 emissions ∼80%, NO x emissions ∼50%, N leaching and runoff 19–38%, and GHG emissions 64–86%. High degrees of provincial food sourcing increased N losses and GHG emissions, because this required the use of less suitable peatland and wet soils, and more ruminants in urbanized provinces. However, 50–75% of consumed N could be sourced locally within provinces without significantly increasing impacts compared with national sourcing. SIGNIFICANCE Nutrient circularity substantially reduced N losses and GHG emissions. Food sourcing at provincial rather than national scale did not further reduce N losses and GHG emissions. In countries with more varied production conditions, benefits and drawbacks of local sourcing are likely more pronounced.