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Resource consumption in LCA: a thermodynamic approach
Stefan Goessling-Reisemann,* University of BremenSome of the impacts measured in LCA have no generally accepted characterisation method. One of them is resource consumption. Some proposed characterisation factors are based on the extraction of material from the earth crust, others are based on the throughput of matter and energy through the assessed production system, and yet others are based on future additional energy expenditure. It has been argued, however, that the methods for assessing resource consumption in LCA must come from thermodynamics, and must take account of the second law of thermodynamics (entropy law). There are basically two different approaches using thermodynamics: exergy loss analysis and entropy production analysis. The challenge arising for both of these methods, especially in respect to its application and software implementation, is the increase in data requirements. While already being a data intensive methodology, including a thermodynamic measure for resource consumption in LCA will increase the data that needs to be handled significantly. This can only be managed by employing thermodynamic data bases and combining these with dedicated LCA software. I will present an approach that makes use of the scriptability of a commercial LCA software and combines it with a thermodynamic database where values are stored in a parameterised form. Processes from the metallurgical sector serve as an illustrative case study. In addition to characterising resource consumption, having calculated the entropy flows through the analysed system highlights the potential targets for a thermodynamic optimisation. Another level of analysis can be reached, when the mixing and unmixing of materials is evaluated using the entropy of mixing. From this conclusions regarding the effectiveness of separation processes (especially recycling processes) can be drawn. In this manner, the LCA process can be accompanied by a technical optimisation using the same material flow model and software as used for the life cycle modelling.
* corresponding author: sgr@uni-bremen.de