Nutrient-extended input–output analysis for food nitrogen footprint

Nitrogen (N) inputs to agro-food systems are ultimately lost to the environment and threaten human and ecosystem health. We developed and applied a novel approach—the nutrientextended input–output (NutrIO) analysis—to evaluate the N footprint.

The method sums N inputs through supply chains by linking a material flow analysis (MFA) of N and economic transactions. The estimated N footprint of Japan in 2011 was 21.8 kg-N capita−1 year−1 (16.7 kg-N capita−1 year−1 sourced from agriculture and fisheries and 5.1 from non-fertilizer chemical industries). The analysis provides a better understanding of N use in complex agrofood systems.