Department of Chemical and Environmental Engineering, University of Oviedo, C/ Julián Clavería s/n, 33071, Oviedo, Spain.
Environ Sci Pollut Res Int. 2020 Jan;27(2):1650-1666. doi: 10.1007/s11356-019-06857-6. Epub 2019 Nov 21.
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 kgCOeq kg). Specifically, in the semi-confinement and the pasture-based dairy farms, 1.22 and 0.99 kgCOeq kg 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 kgCOeq kg of cheese for milk produced in semi-confinement and pasture-based systems, respectively. The production of raw milk represented more than 60% of COeq emissions associated with cheese, so the primary production is the critical factor in reducing the GHG emissions due to cheese making.
牛奶生产估计占人为温室气体（GHG）排放的 3-4%。然而，生牛乳的碳足迹因多种因素而异，例如地理区域、奶牛品种和生产系统。在本研究中，提供了生牛乳碳足迹（CF）研究的全球概述。此外，通过生命周期评估（LCA）分析了两种不同的奶牛养殖系统（半封闭和放牧），以确定它们对所产牛奶 CF 的影响。清单数据直接从这些设施中获得，并包括牛奶生产中涉及的主要因素（副产品、牲畜饲料、水、电、柴油、清洁用品、运输、粪便和泥浆管理、向大气排放的气体等）。与已审查的文献一致，发现牛奶的碳足迹主要由牛的饲养系统和奶牛的气体排放决定。在所研究的系统中发现的牛奶 CF 值在全球奶牛养殖范围内（0.9-4.7 kgCOeq kg）。具体而言，在半封闭和放牧奶牛场，分别获得 1.22 和 0.99 kgCOeq kg。放牧系统带来的环境效益不仅主要归因于对购买饲料的低利用，还归因于牛奶和肉类的分配，这被发现是 CF 计算中的一个决定性方法因素。最后，评估的奶牛养殖系统的数据被用于分析生牛乳生产对奶酪制造的影响。为此，还获得了一家小型奶酪工厂的 CF。包括奶酪工厂清单中的主要子系统（原材料、水、电、能源、清洁产品、包装材料、运输、废物和气体排放）。半封闭和放牧系统生产的牛奶的 CF 值分别为 16.6 和 14.7 kgCOeq kg 的奶酪。生牛乳的生产占奶酪相关 COeq 排放的 60%以上，因此初级生产是降低奶酪生产导致温室气体排放的关键因素。
