TECHNOLOGY | PET RECYCLING


polyesters from coloured, colorless, transparent, and opaque bottles and from textiles that are 100% polyester as well as mixtures like PU, cotton, polyether, and polyurea with up to 30% of pres- ence in the textile, the company said. Chinese research organisation Nanjing Institute


of Environmental Sciences (NIES), has conducted work on biotic and abiotic recycling and upcycling strategies for PET as an avenue toward enhancing the efficiency and environmental sustainability of PET recycling. Li Wei, a senior environmental scientist, and Zhang Ming, a polymer chemist, led research of this innovative approach at NIES that is based on the integration of biotic and abiotic processes to optimise the breakdown and repurpos- ing of PET. The paper was published this year in the peer-reviewed journal Eco-Environment and Health.


Above: Gr3n’s facility in Spain has started construction: image shows how it will look when it is complete


offers recyclers the ability to process PET flexibly, ensuring that diverse sources of plastic waste can be handled efficiently. This is a critical improve- ment over older systems that require strict feed- stock specifications, said Crippa. Traditional chemical depolymerisation processes


often require high temperatures and prolonged reaction times, consuming large amounts of energy and contributing to higher greenhouse gas emis- sions, said Crippa. By utilising microwave technol- ogy, Gr3n’s process operates at lower temperatures and shorter cycles, resulting in reduced energy costs and a smaller environmental footprint. Gr3n’s technology competes directly with


traditional chemical recycling methods, such as glycolysis and methanolysis, which rely on bulk heating and can involve hazardous chemicals and extensive processing times. Mechanical recycling, another prevalent method, sometimes results in downcycled products of lower quality due to polymer chain degradation and contamination. By contrast, Gr3n’s microwave-assisted approach offers a scalable solution that maintains the integrity of recycled materials. Gr3n earlier this year signed a Memorandum of Understanding with Spanish engineering company and shareholder Intesca Industrial to set up a facility in Spain. The partners have started the first phase of construction of the facility which aims to produce 40,000 tonnes/yr of virgin-like PET from hard-to-recycle PET materials such as textile waste, when it becomes operational in 2027. The new facility will produce PET chips from the


recycled monomers, saving nearly 2m tonnes of CO2


32 PLASTICS RECYCLING WORLD | November/December 2024


during its operational life. It will be designed to process post-consumer and/or post-industrial


Dual strategy According to the researchers, biotic recycling employs biological agents – specifically, enzymes and certain strains of bacteria and fungi – to degrade PET at a molecular level. Abiotic recycling, on the other hand, leverages non-biological processes, including chemical and thermal meth- ods, to depolymerise PET. The innovation from NIES lies in the synergistic combination of these two methods. The dual strategy significantly increases the yield of monomer recovery while maintaining environmental and economic viability. Li Wei said: “We have discovered that pre-treat-


ing PET with controlled thermal or chemical processes can enhance the efficiency of subse- quent enzyme-based degradation. This combina- tion reduces the overall energy demand and speeds up the breakdown process.” This combined approach offers multiple benefits


over traditional mechanical recycling, which often degrades the quality of PET over successive cycles. By reverting PET to its monomers through biotic- abiotic integration, the resulting material retains the same quality as virgin PET, enabling endless recycling without loss of properties. Zhang Ming said the work addresses the main limitations of conventional recycling by providing a method that preserves material integrity. The reduced energy consumption of enzyme-driven processes, paired with strategic thermal pre-treatment, leads to a lower carbon footprint compared to purely chemical methods. Additionally, the research explores upcycling


strategies that transform PET waste into higher- value products. By adjusting the enzyme formula- tions and reaction conditions, the team has success- fully converted PET’s monomers into specialty


www.plasticsrecyclingworld.com


IMAGE: GR3N


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