Nitrogen loss in a region with developed food industries: a new method of nitrogen flow and recyclability analysis focusing on distribution system

The present study investigates nitrogen (N) flows within the food system of Yamanashi Prefecture from 2000 to 2015, by longitudinally integrating Input–Output analyses with N flow models. By unveiling detailed N flows specifically in the food manufacturing sector (food processing, distribution, and food service), this study aims to analyse the recyclability of N losses quantitatively. Results showed approximately 60% of the total N input resulted in N loss. The N losses can be classified into highly recyclable nitrogen (high-RAN: 11%), low-recyclable nitrogen (low-RAN: 16%) and non-recyclable nitrogen (non-RAN: 73%). A comparative analysis was performed with three scenarios according to the Green Food System Strategy: a control scenario of 2050, Scenario l targeting chemical fertilizer reduction, and Scenario 2 targeting chemical fertilizer reduction and increased feed self-sufficiency. Compared to the control, both Scenario 1 and Scenario 2 demonstrated improvements in N recycling efficiencies by 4.9% and 15.0%, respectively. Notably, the Scenario 2, which separately reutilised high-RAN and low-RAN, expanded the N demand for recycling, achieving a 6.4% enhanced N loss reduction compared to the Scenario 1. In conclusion, this study provides the suggestion that the sophistication of the reutilisation network can promote the reduction of N losses.