Detailed nitrogen and phosphorus flow analysis, nutrient use efficiency and circularity in the agri-food system of a livestock-intensive region

The agri-food value chain is a major cause of nitrogen (N) and phosphorus (P) emissions and associated envi-ronmental and health impacts. The EU's farm-to-fork strategy (F2F) demands an agri-food value chain approach to reduce nutrient emissions by 50% and fertilizer use by 20%. Substance flow analysis (SFA) is a method that can be applied to study complex systems such as the agri-food chain. A review of 60 SFA studies shows that they often lack detail by not sufficiently distinguishing between nodes, products and types of emissions. The present study aims to assess the added value of detail in SFAs and to illustrate that valuable indicators can be derived from detailed assessments. This aim will be attained by presenting a highly-detailed SFA for the livestock-intensive region of Flanders, Belgium. The SFA distinguishes 40 nodes and 1827 flows that are classified into eight different categories (e.g. by-products, point source emissions) following life cycle methods. Eight novel indicators were calculated, including indicators that assess the N and P recovery potential. Flanders has a low overall nutrient use efficiency (11% N, 18% P). About 55% of the N and 56% of the P embedded in recoverable streams are reused providing 35% and 37% of the total N and P input. Optimized nutrient recycling could replace 45% of N and 48% of P of the external nutrient input, exceeding the target set by the F2F strategy. Detailed accounting for N and P flows and nodes leads to the identification of more recoverable streams and larger N and P flows. More detailed flow accounting is a prerequisite for the quantification of technological intervention options. Future research should focus on including concentration and quality as a parameter in SFAs.

Automated summary

The agri-food value chain is a significant contributor to nitrogen and phosphorus emissions and their impacts. The EU's farm-to-fork strategy aims to reduce nutrient emissions and fertilizer use. Substance flow analysis is a useful method for studying the agri-food chain, but current studies lack detail in distinguishing between nodes, products, and emissions. This study presents a highly-detailed SFA for the livestock-intensive region of Flanders, Belgium, which identifies recoverable streams and calculates novel indicators. Optimized nutrient recycling could exceed the targets set by the F2F strategy. Future research should consider concentration and quality in SFAs.