Process simulation and life cycle analysis in the dairy industry – application to milk powder production

The design and development of sustainable food processes, which integrate technical and economic criteria, satisfy customer demands, and are less harmful to ecosystems constitutes a major challenge in a context of global changes (climate change, energy scarcity and energy price increase,...). An interesting way to meet these constraints entails a systemic approach combining modelling, simulation, and optimisation. Although methodological tools have been developed in the chemical industry (Steffens et al. (1999), Azapagic et al. (2011), Ouattara et al. (2012)), this kind of approach suffers from a lack of available models that can be applied in the food processing industry. The aim of this work is to develop a framework for the ecodesign of food processes, with a focus on sustainable milk proteins concentrating systems. A systemic approach is proposed in this paper, involving process modelling and simulation of a highly energy-consuming milk process coupled with its associated environmental assessment. More precisely, the approach combines the use of a flow-sheet simulation software tool with a commercial Life Cycle Assessment (LCA) software tool. The process to be studied leads to the production of milk powder from whole milk. The main principle is to concentrate a fat-standardised milk with a number of unit operations, i.e., skimming, homogenisation, pasteurisation, evaporation, and spray drying. The energy consumption of concentration and drying processes alone accounts for 25% of the dairy processing industry energy consumption. These operating steps thus require to be optimized to improve the overall performance of the whole process evaluated through the proposed systemic approach. Literature review about process simulation and environmental analysis in the milk industry demonstrated that both aspects are seldom simultaneously treated: environmental assessment is mostly achieved with fixed process operating conditions. The analysis of the necessary degree of granularity of the related models could lead to the selection of the Aspen Plus® (Aspen Technology, Inc.) software, because of its substantial unit operation models library, and a strong capacity to integrate and model new components (not included in its built-in database). The simulation results give the material and energy flows, which are analysed and compared with experimental results. The LCA of the process is performed with the SimaPro® software, and then discussed from a multicriteria point of view. Finally, the extraction of the environmental database of the milk powder process from EcoInvent makes it possible to carry out sensitivity analyses, and suggest scenarios which are interesting both from economic and environmental viewpoints.