Carbon fiber recycling from composite: A multimethodological approach combining pyrolysis experimental data, energy modeling, and environmental analysis

The study presents an integrated technical-environmental impact of carbon-fiber recycling from carbon-fiber-reinforced composites (CFRCs) through pyrolysis, combining experimental tests, parametric energy modelling, and life cycle assessment (LCA). Preliminary LCA, based on literature data comparing pyrolysis with mechanical and chemical recycling, identified energy demand as hotspot. Pyrolysis was tested at laboratory scale yielding 66.2 ± 2.4 % solid product, 12.1 ± 5.0 % oil, and 21.7 ± 2.7 % gas and 70 % of virgin mechanical properties. The obtained fibers showed high carbon content (>87 %wt) and limited resin residues (1–2 %wt). Experimental data were used to design a parametric model estimating process energy requirements under 200 kg/h. Experimental data and energy-modelling were applied in final LCA (functional unit: 1 kg CFRC waste). Sensitivity analyses, including inert gas, fuel type, thermal integration, and inert/feed ratio, showed that nitrogen and liquefied-natural-gas represent the lowest-impact configuration, while the inert/feed ratio is the highest one. Process optimization via internal energy-recovery of pyrogas was technologically unfeasible under the conditions investigated whereas the exploitation of 50 % of the oil produced as virgin phenolic compounds leads to a reduction of all the impact categories. The study provides a reproducible, multi-methodological framework and identifies key levers for reducing the environmental burden of CFRC pyrolysis.