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

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.