Life cycle assessment of a detailed dairy processing model and recommendations for the allocation to single products

Purpose This study analyses the environmental impacts referring to dairy products and to the operation of a dairy. The study aims to better understand different process stages in a dairy operation. This analysis can be used to improve the flows of energy, water, and materials in the dairy operation. The results are also used to suggest an improved allocation model for assigning the impacts of operation to single dairy products. Methods The analysis is based on a detailed, product-specific model calculation for the use of energy, water, and chemicals for more than 40 subprocesses of a dairy operation. This model has been used to elaborate the life cycle inventory for a detailed life cycle assessment study. The environmental impacts are analyzed from cradle to gate including and excluding the raw milk input. The environmental impacts are assessed with the midpoint indicators suggested by the International Reference Life Cycle Data System. Finally, results of this study are compared with an allocation model recommended for life cycle assessment (LCA) studies on milk products. Results and discussion The analysis of the model dairy shows that raw milk production has the main impact in all categories. Consumer packaging has the second biggest impact in many categories. The detailed dairy processing model allows the assignment of inputs and outputs for each subprocess to single dairy products and thus avoids allocation largely. The analysis of inputs to different dairy products per kilogram shows that ultra-high-temperature (UHT)-processed milk uses more chemicals for cleaning compared to the other products. Cream uses more electricity and heat compared to UHT milk and to yogurt. Conclusions A detailed discussion shows the overlaps and differences found for the allocation of inputs to the milk processing to final dairy products. Allocation models for different types of inputs are partly confirmed by the detailed theoretical model used for this LCA. The allocation of chemicals, steam, and electricity to single products can be improved based on the detailed dairy model developed in this study.