Quality Before Quantity? Considering Material Properties in Prospective Modelling of Recycling

Other conference contribution, 2024

As recycling technologies emerge for materials that have previously not been recycled, new uncertainties arise. These include which impacts the recycling process causes, the quality of the recycled materials, and quality requirements on the recycled materials to be used in a secondary application. In this study, we assess how to include different quality indicators for the secondary material, as well as their influence on the impacts of emerging recycling systems.

We use recycling of carbon fibre composite as a case study to illustrate the influence of the quality indicators on the secondary material when assessing recycling. Carbon fibre composite is a light and strong material, often used to decrease the weight of vehicles and consequently their fuel consumption, but the energy-intensive production phase often counteracts environmental benefits from a lower fuel consumption. However, it has been shown that recycling of the composite and recovery of the fibres for a secondary application could remedy this, if and when implemented at large scale.

This study provides insights on how to choose an appropriate quality indicator in prospective life cycle assessment of recycled materials. We first identify relevant quality indicators for recycled carbon fibres by consulting the industry and carbon fibre experts. We then apply these quality indicators in case studies for two emerging recycling technologies: Microwave radiation pyrolysis and solvolysis by means of acetic acid. Additionally, mechanical treatment and conventional pyrolysis are included as they are the most commonly (yet sparsely) used recycling technologies for carbon fibre today. The emerging technologies with lower technology readiness levels are upscaled to represent an industrial scale.

Preliminary, six relevant quality indicators for recycled carbon fibres are identified. Initial results shows that the environmental impacts are strongly influenced by the choice of quality indicator. We provide suggestions on how these can be included in the prospective assessment, for example by altering the functional unit, or by letting the impacts of the recycling process depend ion what materials can be substituted downstream.