Embodied energy of pyrolysis and solvolysis processes for recycling carbon fiber reinforced polymer waste

Abstract

Composites are being increasingly used in aerospace, automotive, energy, gas storage, marine, infrastructure, sporting goods, and other secondary industries. The key drivers for composites is light weight, high specific strength, and durability. The composites market is projected to grow from $72.58 billion to $115.43 billion by 2022 (CAGR of 8.13% between 2017-2022) with carbon fiber demand alone projected to soar to 150,000 metric tons by 2020 globally, implying that much of this will reach their End-of-Life (EOL) stage in the coming years. Due to rising disposal cost of landfills and lack of space, it is important to diversify composite waste streams in order to address feasible options related to recovery, reuse, and remanufacture. The Institute for Advanced Composites Manufacturing Innovation (IACMI) has partnered with several industry collaborators to address the issue of carbon fiber reinforced polymer (CFRP) waste. This paper highlights the significance, complexities, application, and the embodied energy (EE) associated with two types of recycling processes for EOL CFRP. The cumulative energy demand (CED) method was applied to analyze the pyrolysis and solvolysis processes using the life cycle assessment (LCA) software SimaPro v.9.0.0.33 and the FRPC Energy Use Estimation Tool developed by the Oak Ridge National Laboratory. Data was sourced to model the amount of fiber, resin, and embodied energy that may be recovered from each recycling system considering 1 kg of carbon fiber-epoxy laminate as benchmark. It was found that a continuous natural gas furnace based pyrolysis system consumes a total of 52 MJ/kg by default and 42 MJ/kg while reusing syngas generated within the system as avoided energy. The supercritical solvolysis process considered for analysis presented a total embodied energy of 257 MJ/kg.