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The comparative hybrid life cycle assessments and sustainability of functional devices and related materials

Lucy Smith

A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy


Professor I. M. Reaney

Professor S. C. L. Koh

Department of Materials Science and Engineering

The University of Sheffield

May 2019


To begin, I would like to express my sincere gratitude to Professor Ian M. Reaney and Professor S. C. Lenny Koh for their supervision and support throughout this PhD journey. Their knowledge and experience in their respective fields has helped me tremendously in developing as a researcher. Furthermore, I am extremely thankful for the opportunities that they have provided through attending and presenting at global conferences and applying my skills to wider projects. Finally, I am thankful for the financial support provided through the SUbST grant, allowing me to achieve the goal of completing a PhD.

Special thanks go to Dr. Taofeeq Ibn-Mohammed for his help and support throughout this process. His knowledge and expertise in the application of hybrid life cycle assessment helped me to further my own understanding and produce robust and reliable results.

I would further like to thank Professor Derek C. Sinclair and Dr. Fan Yang for their help in my understanding of intermediate temperature SOFCs. To Jean Simpson, I give my thanks for providing additional opportunities and funding alongside my studies. To the Armourers and Brasiers’ Company for the travel grant which allowed me to present at the “Second Global Conference on the Theory and Applications of OR/OM for Sustainability” in Beijing in September 2017. Also, to my friend Dr. Giulia Poerio, who set me off on the right track for the statistical analysis required for the development of the MSI.

My family and friends, both outside and inside of the University of Sheffield, have been unwavering in their continued support and understanding throughout the period of my PhD, especially when (I thought) things were getting tough.

Finally, I wouldn’t be here today without the person who puts up with me on a day to day basis, provides me with ongoing support, grounds me when needed and always makes me laugh. Tony, thank you.


The world-wide demand for complex products is a challenge in the race to achieve global “sustainability”. As a society, our natural resource consumption and environmental pollution must be hampered in order to achieve a number of the United Nations Sustainable Development Goals. To date, a single methodology for the assessment of sustainability has not been presented, furthermore, a specific calculation to determine the sustainability of a material is absent.

As functional materials, and their associated devices, underpin many of the technologies that we rely on in modern life, from energy generation to communication and transportation, their contribution to global sustainability is of high importance. Despite this, the impact of these components on the environment are not widely studied.

With this in mind, the information presented in this thesis is three-fold. To begin, three comparative hybrid life cycle assessments (HLCAs) of; multi-layered ceramic capacitors (MLCCs) and tantalum electrolytic capacitors (TECs), high temperature and intermediate temperature solid oxide fuel cells (SOFCs) and lithium ion batteries (LIBs) and solid state batteries (SSBs) are outlined. The results of these HLCA are assessed within each system boundary. Secondly, a simple, robust calculation to assess the sustainability of a material, referred to from this point on as the Material Sustainability Index (MSI), is presented along with the underpinning methodology and detailed assessment of the final results. Finally, the results of the HLCA, the MSI and other existing measurements are compared.

Comparison of the environmental impacts of MLCCs and TECs shows that, from cradle-to-grave, the use of tantalum in TECs and nickel in MLCCs lead to the material carbon hot-spots within each supply chain. The results of this study show that the electrical energy requirement of MLCCs is higher than that of TECs but the material embedded energy requirement is found to be twenty times that of MLCCs. The impact of dysprosium use within the MLCC structure was diluted by the high electrical energy requirements and therefore not highlighted as a carbon hot-spot, this emphasises the need for modellers to consider assessing materials and components using multiple methodologies, for example criticality.

When the environmental impacts of high and intermediate temperature SOFCs were compared, the results indicated that the use of novel material structures for intermediate temperature SOFCs results in an impact reduction when compared to high temperature SOFC material architectures. This is due to a reduction in primary energy demand, though an increase in electrical energy is required to allow for the increasingly complicated manufacturing processes employed for the production of these novel structures.

While the results of the comparative HLCA of LIBs and SSB found that the environmental impacts of material use in SSBs are lower than those relating to LIBs, the high electrical and thermal energy demand relating to SSBs far outweighs that relating to LIBs. Despite this, this energy requirement is likely to decrease in an industrial manufacturing environment through the use of more efficient processing techniques and processing aids.

The MSI, a composite indicator consisting of four individual indicators, provides a single result relating to the sustainability of a material. Overall, a large percentage of materials have a final MSI value of 0 points, due to a recycling rate of 0%. In general, it is the social aspect, which is accounted for using the Human Development Index that has the highest impact on the final result with the Global Warming Potential and National Economic Importance of each material having a smaller impact.

Over the period of 2005 to 2015, sustainability decreases for those materials assessed which are linked to an increase of the environmental impact of a process when output is low. Furthermore, the sustainability of a material can be improved through increasing its recycling rate and decreasing the environmental impact relating to its extraction.

When the results of the MSI are compared to those of the HLCAs and other available data sets, it is clear to see that the simple and robust MSI tool should not be viewed as a replacement for other metrics, but as a complementary tool, highlighting the need for concern and further study.


Publications to date 11 List of Tables 12 List of Figures 15 Abbreviations 19 1. Introduction 1 1.1. Aims and objectives 1 1.2. Novelty and contributions 2 2. A review of published literature 4 2.1. Sustainability 4 2.2. Measuring sustainability 6 2.2.1. Life cycle assessment 7 Life cycle assessment methodologies 8 Life cycle assessment data collection 10 Application of life cycle assessment to functional ceramics and related devices 11 Environmental impact categories 12 Component level analysis 13 Material level analysis 17 Limitations of Life Cycle Assessment 18 Sustainability of functional ceramics and related devices 18 Use of critical materials 19 Summary of the application of LCA to functional ceramics and related devices 20 2.2.2. Life cycle costing 20 2.2.3. Social life cycle assessment 20 2.2.4. Sustainability indicators 21 General sustainable development indices 21 Material sustainability assessment specific literature 23 2.2.5. The impact of sustainability on policy 45 2.3. Developing a composite indicator 47 2.3.1. Theoretical framework 50 2.3.2. Missing data 52 2.3.3. Normalisation 53 2.3.4. Weighting and aggregation 56 2.3.5. Uncertainty and sensitivity 58 2.3.6. Revisiting the data 59 2.3.7. Links to other indicators 59 2.3.8. Visualisation of the results 61 2.4. Summary of reviewed literature 61 3. Hybrid life cycle assessment methodology 63 3.1. General HLCA methodology 63 3.1.1. General limitations of the HLCA methodology 65 3.1.2. Overview the HLCA studies 66 3.2. Hybrid Life Cycle Assessment and Environmental Profile Evaluations of High Volumetric Efficiency Capacitors 67 3.2.1. Introduction 67 3.2.2. Methodology 70 3.2.3. Results 86 3.2.4. Discussion 94 Primary energy consumption 94 Component level analysis 95 Comparison of environmental profiles 97 Impacts of end of life methodologies 97 Limitations of this study 100 3.2.5. Conclusion 100 3.2.6. Further research 101 3.3. Comparative Environmental Profile Assessments of Commercial and Novel Material Structures for Solid Oxide Fuel Cells 102 3.3.1. Introduction 102 3.3.2. Methodology 103 Commercial SOFC manufacturing process 104 IT-SOFC, with ESB electrolyte, manufacturing process 105 IT-SOFC, with NBT electrolyte, manufacturing process 106 Production of a functioning SOFC 106 Data collection 106 3.3.3. Results 118 3.3.4. Discussion 123 Comparison of environmental profiles 124 Primary energy consumption 125 Component level analysis 126 Use of critical materials 127 Limitations 128 3.3.5. Conclusion 129 3.3.6. Further research 129 3.4. Comparative Hybrid Life Cycle Assessment of Solid State Batteries as a replacement for Lithium-Ion Batteries 131 3.4.1. Introduction 131 3.4.2. Methodology 132 Lithium-ion battery manufacturing process 134 Solid state battery manufacturing proc