Nitrogen food-print: N use related to meat and dairy consumption in France
Human foods typically contain a minor fraction of the nitrogen (N) used in agricultural production. The major fraction is lost to the environment and interferes with all current environmental problems and global change issues. Food is also generally consumed far from its production location and associated N losses remain unknown unless connected to products through consumption-based indicators. We develop the N food-print as an indicator to connect N flows and losses in livestock systems to the consumption of dietary N in the form of beef, pork and fresh milk in France. This N food-print of a product is the N loss associated with its agricultural production. The conversions of N, from field application to recovery in vegetal and animal proteins, are calculated from statistical data on crop and animal production and through modelling of feed rations for cattle and swine. Beef farming to feed an individual in France uses 11.1 kg N cap −1 yr −1, out of which 3.8 kg N cap −1 yr −1 (or 35%) is the N food-print, 7% is recovered in retail products, 3% is slaughter waste and 55% returns to agriculture as manure. Pork and dairy production use 7.5 and 2.3 kg N cap −1 yr −1, respectively, out of which 53 and 48% is the N food-print, respectively; about 11% is recovered in retail products and 35% returns to agriculture as manure. In total, more than 75% of the N food-print relates to crop cultivation for feed and much of these losses (80% for dairy and pork production, 20% for beef production) occur in crop farms far from where the livestock is reared. Regional and national policies to reduce N losses should take into account that trade in feed implies causal relationships among N losses in agrosystems distant from each other.