Energy intensity and environmental analysis of mechanical recycling of carbon fibre composite

The increased usage of composites in industry coupled with European Union restrictions on landfill disposal has resulted in an urgent need to develop resource efficient recycling technologies. The purpose of this work was to model the electrical energy requirements of milling as a recycling option for carbon fibre composite. By separating the contributions to the total energy required of the machine tool, material cutting energy and material removal rate, the energy demand of carbon fibre composite recycling can be theoretically calculated for any milling process. The model was validated experimentally by comparing the theoretical energy demand to the measured energy demand of an industrial scale milling machine. It was found that at a processing (recycling) rate of 10 kg/hr, the specific energy was significantly less than the embodied energy of virgin carbon fibre (2.03 MJ/kg compared to approximately 200 MJ/kg). Although the form of the recyclate fibres (short, single filaments and bundles) was vastly different to their virgin equivalents (continuous tows), the energy difference highlights the potential environmental benefit of utilising recyclate fibres in place of virgin ones in short fibre composites where mechanical performance is less critical. The relationship between specific energy of recycling and processing rate was also calculated, which highlighted that further energy savings can be achieved at higher processing rates. This work is fundamentally important to provide new data sets for Life Cycle Assessment in order to assess the potential environmental benefits of utilising recyclate fibres.