Advancing prospective life cycle assessment -Experiences from guiding carbon fibre composite development

Abstract: Life cycle assessment is a powerful tool for quantifying the environmental impacts of goods and services. While most easily done for well-defined and known systems, there is also a need for a prospective approach to assess developing technologies. This is because choices made in the early stages of technology development greatly influence the environmental impact of the final product systems.   A material becoming increasingly popular on the larger market is carbon fibre composites, a popular application being in vehicles. The relatively light and strong carbon fibre composites can significantly reduce vehicles’ weight and, therefore, the impact of the use phase. Carbon fibres are, however, based on a fossil raw material, and their production is highly energy intensive. This means that if used in a vehicle, there might not be an overall environmental benefit from a life cycle perspective. In fact, the use of carbon fibre composites might even increase the vehicles life cycle environmental impact. As a result, the carbon fibre composite manufacturing process needs to be changed.   In this thesis, I present a screening method to be used in the early stages of material development research projects when primary data are scarce. I also provide recommendations on how to allocate benefits and burdens between life cycles and co-products in prospective studies. Moreover, I reconceptualization the composite recycling process to a multi-output separation process, which leads to allocation between composite components as well as life cycles. In addition, I provide three consistent future scenarios developed for carbon fibre composites. Finally, advice on how to make systems comparable in prospective contexts is also included.