A critical review of the recent evolution of Life Cycle Assessment applied to milk production

Life Cycle Assessment (LCA) is one of the key tools for the evaluation of the environmental sustainability of the agricultural sector. LCA related to milk production has gained attention in recent years, but the results are often discordant and conditioned by the practitioners’ choices. This has made it difficult to clearly identify the most environmentally friendly way to produce milk. In the present paper, 44 milk LCA studies published after 2009 are reviewed, in order to evaluate the level of harmonization and comparability of methods and results, and to discuss emerging issues and hot topics that would be worth further investigation. Furthermore, the effects that the choice of functional unit and allocation rule could have on the results were statistically analyzed. The understanding of the current research direction of milk-LCA studies is useful to promote a more responsible and sustainable livestock production in the perspective of increasing animal protein demand. This review highlighted the difficulties encountered in comparing milk LCA studies, underlining the importance of practitioners’ choices in determining the results. Harmonization among LCA studies applied to the milk sector still represents a goal to be achieved. It appeared that future LCAs should investigate a broad range of impact categories, including biodiversity and water consumption; define one or more common functional units; improve transparency, giving a detailed description of system boundaries and reporting the method used for impact calculation; and systematically conduct a sensitivity analysis for a better understanding of the effects of the choices of method.