Environmental impacts of dairy system intensification: the functional unit matters!

In the current context of the end of dairy quotas, the increasing size of dairy farms and the expected growth in food demand, European dairy production systems are facing major challenges. The aim of this study was to assess environmental impacts of dairy system intensification to identify production systems that combine high productivity and low environmental impacts. We used the concept of the Technological Management Route, i.e. a logical set of technical options designed by farmers, to describe the diversity of milk production systems in France. Life Cycle Assessment was used to estimate impacts of these systems according to two functional units: t milk and hectare of total (on- and off-farm) land occupied. Dairy system intensification has three major effects: i) an increase in all impacts when expressed per hectare, ii) a decrease in eutrophication and land occupation per t milk, and iii) no clear effects on other impacts when expressed per t milk. The two first effects are due mostly to the switch from grass-based feed to maize silage and concentrate feed when intensifying production systems. Furthermore, the choice of functional unit leads to radically different conclusions. Using only a mass-based functional unit, which is predominant in current life cycle assessment practice, does not provide a balanced view of the impacts of intensification and could mislead decision makers in identifying promising dairy systems. More generally, current LCA practice seems largely blind to the negative environmental consequences of agricultural system intensification, as revealed by the area-based functional unit. Therefore, we recommend the use of both mass-based and area-based functional units in life cycle assessments of agricultural goods.