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

Doctoral thesis, 2023

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 product systems, there is also a need for a prospective (that is, a future-orientated) approach to assessing developing technologies. This is because choices made in the early stages of technology development greatly influence the environmental impact of final product systems.
 
An increasingly popular range of materials on the market is carbon fibre composites, with a common 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. However, carbon fibres are based on a fossil raw material and their production is highly energy-intensive. This means that if used in a vehicle, there may be no overall environmental benefit from a life cycle perspective. In fact, the use of carbon fibre composites might even increase the environmental impact of vehicles’ life cycles. Thus, the carbon fibre composite manufacturing process needs to be changed.
 
In this thesis, I present an environmental screening method to be used in the early stages of material development research projects when primary data is scarce. I also provide recommendations on how to allocate benefits and burdens between life cycles and co-products in prospective studies. Moreover, I reconceptualise the composite recycling process into a multi-output separation process, which leads to an allocation between both composite constituents and life cycles. I also provide three consistent future scenarios developed for carbon fibre composites. Finally, I include advice on how to compare immature to mature technologies in prospective life cycle assessments.