Water-Energy-Food nexus index proposal as a sustainability criterion on dairy farms

Cow milk is a fundamental nutrients source for the human diet at all stages of life. However, the decline in cow milk consumption over the years has been driven by increased consumer awareness of animal welfare and the environmental burdens associated. In this regard, different initiatives have emerged to mitigate the impacts of livestock farming, but many of them without addressing the multi-perspective view of environmental sustainability. Thus, the Water-Energy-Food (WEF) nexus emerges as a framework to consider the complex synergies among carbon emissions, water demand, energy requirements and food production. In this study, a novel and harmonised WEF nexus approach has been proposed and applied to evaluate a set of 100 dairy farms. For that, the assessment, normalisation, and weighting of three lifecycle indicators such as carbon, water and energy footprints, as well as the milk yield were carried out to obtain a single value, the WEF nexus index (WEFni), which varies from 0 to 100. Results show that the WEF nexus scores obtained vary from 31 to 90, demonstrating large differences among the farms assessed. A cluster ranking was performed to identify those farms with the worst WEF nexus indexes. For this group, consisting of 8 farms with an average WEFni of 39, three improvement actions focused on the feeding, digestive process and wellbeing of the cows were applied to determine the potential reduction in the two main hotspots identified: cow feeding and milk production level. The proposed methodology can establish a roadmap for promoting a more environmentally sustainable food industry, although further studies are still required in the pathway of a standardised WEFni.