## 2 Thermal Pyrolysis
### Feedstock Closed-Loop Disposal  
Plastic waste materials are a type of polymer that comes in a wide range, of which poly(ethylene terephthalate) makes up a significant share. According to [38], a huge portion of total PET (polyethylene terephthalate) output, which includes materials such as films, plastics, and fibres, is recycled using diverse technologies and for a wide range of applications, making PET one of the most recycled polymers. It is generally triggered by the PET application option for the direct reuse of uncontaminated old plastic, sometimes known as \"closed-loop recycling.\" From an ecological standpoint, recycling in a closed loop is the best option. However, because of the combination of multiple types of materials, the method in which the material is developed and used in consumer goods is restricted in many ways. This is because, at the end of a product's life cycle, fractions of different origins are subjected to different separation and recycling processes. To make closed-loop recycling better, waste management needs to be more proactive and friendly to the environment, and political efforts need to focus on obtaining funds for developing and making new recycling technologies [39].  
Other difficulties arise when attempting to recycle complex composite materials. The fundamental difficulty in processing composite waste is the variety of physicochemical properties, and composites are difficult to recycle due to the use of crosslinked thermoset polymers in their matrix, which cannot be remelted or remoulded [40; 41]. Composite waste that is difficult to recycle includes wind turbine waste blades. Wind energy is a renewable, limitless, and energy-efficient energy source. In 2020, the worldwide wind power industry installed more than 93 GW, bringing the total to 742.7 GW (707.4 GW onshore and 35.5 GW offshore) [42]. The global wind energy industry uses 2.5 million tons of composite materials. Recycling and reusing waste blades is the most effective way to safeguard the environment and encourage long-term growth. Pyrolysis and gasification are two thermal recycling processes for such waste, with TRL levels of 9 and 5/6 [43; 44]. Pyrolysis can degrade the fibre quality by leaving oxidation residue or char on the fibres or by damaging their chemical structure. Gasification may be facilitated by energy recovery processes, the stream of chemical precursors it produces, and a higher heat-transfer efficiency. A chemical recycling approach based on solvolysis is another viable option for this type of composite waste. Most resin samples are epoxy resins, which, as previous research has demonstrated, require organic solvents and long reaction times to break them down and separate them from glass fibres. According to a previous study's findings and analysis, solvolysis removed complex, frequently multi-component wind turbine blade waste matrices. An organic catalyst-alcohol solution can be used to chemically recycle (solvolyze) cured epoxy resins by fast transesterifying ester bonds with an alcohol to dissolve samples of wind turbine blades. The solvolysis of wind turbine blades allowed for the chemical recycling of both glass fibres and epoxy resin oligomers. Depending on the solvents utilised and the processing conditions, this procedure can take place in an inert N\({}_{2}\) environment at temperatures ranging from 100 to 190 \({}^{\circ}\)C. The resin breakdown rate of this method reached 90%. Different solutions with the option of adding different supplements and opportunities for polymeric materials pyrolysis were reported.