# The Carbon Footprint of Milk Production on a Farm
## 3 Results and Discussion  
Stages of Calculating the Product Carbon Footprint, the Application of LCA Methodology, and the Calculation Approaches  
The calculation of the product carbon footprint (PCF), including that for milk production, comprises several key stages in accordance with standards such as the GHG Protocol Product Life Cycle Accounting and Reporting Standard [30,31]. This is closely related to the life cycle assessment (LCA) methodology outlined in standards ISO 14040 [10] and 14044 [11]. The stages of the analysis include the following [32]. 1. Determining the objective and scope of the study, which involves the following. (a) Identifying the purpose of the analysis, which may be to determine the carbon footprint of milk production on a farm or along the entire production chain, milk consumption, and packaging handling. It may also involve a comparison of the CF values from different groups of farms (e.g., farm size) or two products, e.g., organic and conventionally produced milk. (b) Selecting and determining the system boundaries, i.e., which treatments and processes will be considered in the analyses. Does the research end with milk production on the farm, or perhaps at the entrance or exit gate of the dairy, or does it also take into account further distribution of milk, preparation and consumption, and disposal/recycling of packaging? (c) Determining the functional unit for which greenhouse gas emissions are calculated, e.g., 1 litre of milk, 1 kg of milk, 1 kg of FPCM, 1 kg of cheese, 1 dairy cow, etc. 2. Collecting input data based on specific system boundaries, e.g., acquisition of raw materials (fertilisers, feed materials, feed); production (energy use, fuel consumption); distribution and transport (fuels and energy in transport and storage); use (storage, processing at the consumer's premises); or waste management (recovery, recycling or landfilling). Depending on the LCA accuracy, the data may originate from actual measurements (e.g., detailed, simplified LCA) but also from existing databases or estimates (simplified, screening LCA). 3. Calculating greenhouse gas emissions for all the treatments and processes taken into account in the analysis, based on relevant emission indicators for different greenhouse gases (e.g., CO\({}_{2}\), N\({}_{2}\)O, CH\({}_{4}\)) to carbon dioxide equivalents (CO\({}_{2\,\mathrm{eq}}\)), most often using commercially available software dedicated to performing life cycle assessment or carbon footprint analysis. By using the software, various methodologies for environmental impact assessment that consider greenhouse gas emissions can be easily applied. 4. Interpreting the results, enabling the quantitative determination of greenhouse gas emissions per selected functional unit, both for the product and individual stages of its production or logistics. At this stage, it is possible to identify stages with high CF levels and propose solutions for reducing emissions, such as using green energy or more efficient transportation. 5. Reporting emissions considering greenhouse gas emissions in terms of the CO\({}_{2}\) eq. The documentation should include all the assumptions, restrictions, data sources and methodology for each of the four stages of the carbon footprint calculation outlined above. It is essential to note that for more detailed analyses (e.g., detailed LCA), ISO 14044 standards [11] require the use of an external critical review to ensure the transparency and impartiality of the study, as well as compliance with ISO standards. The choice of LCA methodology has a significant impact on the carbon footprint calculation results. [PERSON] [33] emphasised that the comparability of CF results between studies is limited by the strong heterogeneity of the LCA methods applied, including different system boundaries, allocation methods and the selection of a functional unit. [PERSON] et al. [1] demonstrated that the application of system expansion significantly reducesthe share of emissions attributable to milk, as compared with the allocation methods.