Climate Change and Photochemical Ozone Creation Potential Impact Indicators of Cow Milk: A Comparison of Different Scenarios for a Diet Assessment

Simple Summary Milk is one of the most globally produced foods with a growing trend, so its environmental performance needs to be studied. This research assessed the environmental impact of cow milk according to herds' performance through climate change and photochemical ozone creation potential indicators. The quality of feeds was also addressed. Under our conditions, knowing the nutritional characteristics of diets fed to animals as an alternative to tabulated values reduces the estimated impacts of considered indicators.Abstract An estimate of the environmental impact of dairy farms in Northern Italy producing milk for hard cheese (protected designation of origin) has been obtained through a comprehensive life cycle assessment. The estimate focused on climate change (CC) and photochemical ozone creation potential (POCP) indicators, which were evaluated according to the Intergovernmental Panel on Climate Change (IPCC) guidelines and interpreted with the aid of the feeds' composition evaluated using near-infrared reflectance spectroscopy (Foss NIR-System 5000) as well as with a diet evaluation according to the NRC (National Research Council) or the CNCPS (Cornell Net Carbohydrate and Protein System) nutrient requirement modeling. Herds were classified into high-, mid-, and low-performing based on the daily milk yield per cow. A lower impact on indicators was observed as herd performance increased. The high-performing herds had a lower contribution from enteric fermentation (6.30 x 10-1 kgCO2-eq), and the more milk that they produced allowed for a differentiation of CC from land use and transformation (2.39 x 10-1 kgCO2-eq), compared to low-performing herds (3.66 x 10-1 kgCO2-eq). Compared to the IPCC approach, the CC and POCP indicator estimates were reduced when addressing the feed's quality, particularly in mid- and high-performing herds. The results could be helpful in the dairy sector as they provide an insight into how diet quality affects the environmental impact of milk.