PhD Studentship: Chemical Recycling of Next Generation Bio-Plastics

From the litter on our streets to the food that we eat, plastics have contaminated our global ecosystem with an estimated 400 million tonnes produced each year. To tackle this tidal wave of waste, bioplastics, such as poly(hydroxy alkanoates) (PHAs), are emerging as a highly promising alternative to conventional plastics; production of this bioplastic in particular is expected to grow by a factor of 10 by 2028. This will inevitably result in thousands of tonnes of waste. Although they are biodegradable, instead of just letting them decompose in the environment, it is imperative that we capture the value of these polymers at scale; a key challenge which this project seeks to address.

This project will apply chemical recycling techniques to samples of a PHA and screen suitable reaction conditions, solvents, and catalysts with the aim of recovering a pure monomer feedstock. Due to the wide range of variables, a Taguchi design of experiments approach will be harnessed in order to maximise the information gained from a minimum number of datasets. When selecting the recommended operating parameters, particular focus will be given to reducing the overall environmental impact of the process by utilising the principles of green chemistry and engineering. To fully characterise the reaction system, not only will the chemical products be identified and quantified, but the kinetics of the process will also be determined; a vital piece of information when considering industrial scale design.

It is envisaged that the recovered monomers can later be repolymerised to create virgin-quality PHA and thus demonstrate a fully circular economy. As part of this, it will be necessary to purify the product stream, complete the polymerisation reaction, and characterise the final product. A suite of characterisation techniques such as mechanical testing (strength and modulus), spectroscopy (infrared and Raman), and microscopy (scanning electron and atomic force) may be used, in addition to thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and viscometry.

Finally, to ensure that the developed recycling solution is environmentally beneficial, data generated from the process will be used to carry out a life cycle analysis (LCA). Standard procedures (ISO 14044) will be followed to enable comparison to other end-of-life options, along with the manufacture, recycling, and disposal of conventional, petrochemical-based polymers.

This project would be suitable for a graduate from a Chemistry, Chemical Engineering, or similar discipline, with an interest in carrying out experimental work. Some modelling (to determine the reaction kinetics and conduct the LCA) will also be completed. Full training on this, and the analytical techniques to use will be provided. You will also have the opportunity to collaborate with current PhD students and post-doctoral researchers within the School.

Funding notes:
This project is funded by the University of Birmingham and is open to UK students only. The funding covers a stipend payable to the PhD student (£18,622 p.a tax free), home fees (£4,712), and bench fees (~£600 p.a) which covers the cost of lab consumables.

References:
J. G. Rosenboom, R. Langer, and G. Traverso, “Bioplastics for a circular economy,” Nat. Rev. Mater., vol. 7, no. 2, pp. 117–137, 2022, doi: 10.1038/s41578-021-00407-8.

R. Meys, M. Bachmann, B. Winter, C. Zibunas, and S. Suh, “Plastics By a Circular Carbon Economy,” Science, vol. 76, pp. 71–76, 2021, doi: 10.1126/science.abg9853.

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