Carbon fibre reinforced polymer (CFRP) composites have become integral to modern day society, forming the backbone of lightweight, high performance structures in aerospace, renewable energy and automotive applications amongst other. Their exceptional strength-to-weight ratio, stiffness and corrosion resistance in such applications make them indispensable for improving fuel efficiency, thereby contributing to lower greenhouse gas emissions. However, their end-of-life management and recycling remains a critical challenge. The thermoset polymer matrix used in most high-performance CFRP composites, makes fibre-matrix separation difficult leading to limited recyclability and continues reliance on energy- and cost- intensive virgin carbon fibre production.

Among the emerging approaches for CFRP recycling, electrochemical processes have gained attention as promising low-energy and environmentally friendly alternatives to traditional thermal or chemical processes. The electrochemical recycling of CFRP operates under mild conditions, without the need of hazardous solvents or external heating. Despite these advantages, current literature focuses predominantly on fibre recovery efficiency with limited understanding of the gaseous, liquid and solid by-products formed during such process. These by-products may significantly influence the true environmental footprint and industrial feasibility of this technique.

To address this gap, this study systematically investigated the influence of constant applied voltage (4, 6 and 8 V) on by-product generation and CFRP degradation behaviour in an alkaline saline electrolyte composed of 3wt.% NaCl and 0.01M KOH. The by-products were characterised using gas chromatography and proton nuclear magnetic resonance spectroscopy. Additionally, the pH of the electrolytes after electrolysis was monitored and surface analysis techniques were employed to evaluate the degradation mechanisms and fibre integrity.

Results revealed that higher voltages increase current density, gas evolution and epoxy degradation, but also produced greater quantities of CO2, hydrocarbons and liquid by-products, alongside visible fibre damage. Conversely, lower voltages achieved sufficient resin removal while maintaining fibre integrity and reducing emissions. Liquid-phase analysis identified ethanol, acetone and formate, whose decomposition correlated with increasing CO2 evolution at higher potentials.