Milk production has been estimated to contribute 3–4% of anthropogenic greenhouse gas (GHG) emissions. However, the carbon footprint associated with raw milk can vary, depending on a variety of factors, such as the geographical area, species of cow and production system. In this study, a global overview of research published on the carbon footprint (CF) of raw cow milk is provided. Additionally, two different dairy systems (semi-confinement and pasture-based) have been analysed by life-cycle assessment (LCA) in order to determine their effect on the CF of the milk produced. Inventory data were obtained directly from these facilities, and the main factors involved in milk production were included (co-products, livestock food, water, electricity, diesel, cleaning elements, transport, manure and slurry management, gas emissions to air etc.). In agreement with reviewed literature, it was found that the carbon footprint of milk was basically determined by the cattle feeding system and gas emissions from the cows. The values of milk CF found in the systems under study were within the range for cow milk production worldwide (0.9–4.7 kgCO₂eq kgFPCM⁻¹). Specifically, in the semi-confinement and the pasture-based dairy farms, 1.22 and 0.99 kgCO₂eq kgFPCM⁻¹ were obtained, respectively. The environmental benefits obtained with the pasture grazing system are not only mainly due to the lower use of purchased fodder but also to the allocation between milk and meat that was found to be a determining methodological factor in CF calculation. Finally, data from the evaluated dairy systems have been employed to analyse the influence of raw milk production on cheese manufacturing. With this aim, the CF of a small-scale cheese factory has also been obtained. The main subsystems involved (raw materials, water, electricity, energy, cleaning products, packaging materials, transport, wastes and gas emissions) were included in the inventory of the cheese factory. CF values were 16.6 and 14.7 kgCO₂eq kg⁻¹ of cheese for milk produced in semi-confinement and pasture-based systems, respectively. The production of raw milk represented more than 60% of CO₂eq emissions associated with cheese, so the primary production is the critical factor in reducing the GHG emissions due to cheese making.

Milk can be considered as an indicator of the degree of environmental contamination of the place where it is produced and this is especially important when assessing its content in toxic metals. Therefore, 36 bovine milk samples from 7 farms with a semi-extensive grazing system were analysed, located in Asturias (Spain), in an area with high probability of being highly contaminated due to a mining zone, with important industrial activity and near high-density highway traffic. The samples were lyophilised to achieve total dehydration, further analysed using inductively coupled plasma mass spectrometry (ICP-MS). The metals titrated were aluminium (Al), arsenic (As), molybdenum (Mo) and mercury (Hg) in the lyophilised samples and subsequently extrapolated their values to whole milk. All samples analysed showed levels of Al and Mo above the limit of detection, with mean values of Al of 140.89 ± 157.07 in liquid milk and 1065.76 ± 1073.45 in lyophilised milk and Mo of 20.72 ± 14.61 μg/kg and 152.26 ± 96.82 μg/kg in whole and lyophilised milk. Only As was detected in four samples with mean values of 18.45 ± 6.89 and 166.45 ± 42.30 μg/kg in liquid and lyophilised milk, respectively, and no Hg was found in any of them. In no case do the values found indicate a significant hazard to the population and are in agreement with those found in other investigations. Although the various anthropogenic activities of the area (industrial, mining, traffic density) could, a priori, indicate a possibly contaminated area.