Recycling of composite waste by sequential application of multi-criteria decision-making, pyrolysis, and reproduction

This paper summarizes our work aimed at applying different methods sequentially in the evaluation of GFRP (glass fiber reinforced polyester) waste, which is a composite waste according to circular economy assumptions. For this aim, the management alternatives that are defined as mechanical recycling, chemical recycling, pyrolysis, and incineration methods are compared using the ANP (Analytic Network Process) and the VIKOR (Vise Kriterijumska Optimizacija I Kompromisno Resenje) methods. To show the applicability of the pyrolysis, which was determined as the most appropriate method, experiments were carried out at different temperatures. After the general characterization of the products was conducted, the solid product was used to reproduce GFRP. After a tensile strength test of the GFRP, which was produced using fibers obtained from pyrolysis at 500°C, it was found that it had approximately 43.15% more tensile strength than polyester cast without fiber. Following a further oxidation step, the tensile strength increased by 61.50%. The liquid products have the potential to be used as fuel oil, and the gas product is sufficient to provide the energy requirements of a process plant. Pyrolysis proved to be a profoundly feasible method for not only recovering glass fiber, but also energy from GFRP waste.