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A systems approach to plastic waste valorisation

The inherent limitations of conventional mechanical recycling technologies in dealing with highly contaminated plastic waste streams and the economic barriers for new chemical recycling technologies are among the major challenges in maintaining the value of plastic materials within the loop and to achieve a circular economy. Plastic waste that comprises a mixture of materials with variable properties and contamination level needs to be recycled, upcycled or recovered using advanced technologies which are economically promising and environmentally benign. The ultimate goal is to shift from selective plastics recycling (single and homogenous type of plastics) model into an “omnivorous” recycling (including highly contaminated and heterogeneous plastics) model while diverting more plastic waste from landfills and incineration, and preventing leakage to the environment.This project aims to explore existing and emerging technologies for plastic waste valorisation. This project will adopt a whole system approach by considering the collection, transportation, pre-treatment (sorting, washing/cleaning) and reprocessing steps for plastic waste management. This will enable a more in-depth understanding of different technologies/strategies and further facilitate the decision-making process of which pathways could best maintain or maximise the overall value of plastic materials whilst reducing the cost of investment and environmental footprint.Skills and Experience Required:• Computational modelling: This project requires simulation modelling and mathematical optimisation techniques. Software such as Aspen Plus, Matlab, Python and GAMS will be applied.• Sustainability assessment: This project involves rigorous techno-economic analysis and environmental life cycle assessment (LCA). LCA software such as Gabi or SimaPro will be applied.Applicants should have received a First or Upper Second Class honours degree in Chemical Engineering, Environmental Engineering, Chemistry or a similar discipline. Applicants should be highly motivated, able to work independently and in a team, and have good written and verbal communication skills.


1. Ng, K.S., Phan, A.N., Iacovidou, E., Wan Ab Karim Ghani, W.A., 2021. Techno-economic assessment of a novel integrated system of mechanical-biological treatment and valorisation of residual municipal solid waste into hydrogen: A case study in the UK. J Clean Prod. 298: 126706.

2. Ng, K.S., Phan, A.N., 2021. Evaluating the techno-economic potential of an integrated material recovery and waste-to-hydrogen system. Resour Conserv Recycl. 167: 105392.

How to apply

If you are interested in applying for the above PhD topic please follow the steps below:

  1. Contact the supervisor by email or phone to discuss your interest and find out if you would be suitable. Supervisor details can be found on this topic page. The supervisor will guide you in developing the topic-specific research proposal, which will form part of your application.
  2. Click on the 'Apply here' button on this page and you will be taken to the relevant PhD course page, where you can apply using an online application.
  3. Complete the online application indicating your selected supervisor and include the research proposal for the topic you have selected.

Good luck!

This is a self funded topic

Brunel offers a number of funding options to research students that help cover the cost of their tuition fees, contribute to living expenses or both. See more information here: The UK Government is also offering Doctoral Student Loans for eligible students, and there is some funding available through the Research Councils. Many of our international students benefit from funding provided by their governments or employers. Brunel alumni enjoy tuition fee discounts of 15%.

Meet the Supervisor(s)

Kok Siew Ng - Dr Kok Siew Ng is a Lecturer (Assistant Professor) in Chemical Engineering at Brunel University London and an NERC Fellow. He joined Brunel in March 2022 after the completion of his 4-year independent fellowship at University of Oxford. He is also currently the Co-Investigator and Coordinator of the Oxford Agile project (Sprint 2) – a university-wide initiative focusing on tackling various environmental challenges using an interdisciplinary approach, funded through the £10 million NERC Changing the Environment programme. The sprint project aims to develop strategies for determining the best regional combination of nutrient recovery and utilisation options for both economic viability and environmental benefits. Prior to joining Brunel, Kok Siew was a UKRI/NERC Industrial Innovation (Rutherford) Research Fellow and Lecturer in Chemical Engineering at the Department of Engineering Science, University of Oxford, from 2018 to 2022. During his time in Oxford, he was a Principal Investigator for the SYNERGORS project 'A systems approach to synergistic utilisation of secondary organic streams' (£0.5 million), funded by NERC. The project aimed to explore novel approaches to addressing challenges in organic waste management and achieving circular economy. As the first Research Fellow in the Department to be offered a concurrent lectureship contract, he took on the role of delivering comprehensive full-module teaching. This includes conducting lectures, guiding tutorials, managing exams, and overseeing MEng project supervision. He completed his MEng Chemical Engineering with Chemistry (First Class Honours) in 2008, and later gained his PhD in 2011 from the Centre for Process Integration (CPI), The University of Manchester. After completing his PhD, he joined Process Integration Limited (PIL) as a consultant and later took up a position as a Postdoctoral Research Fellow at the Centre for Environment and Sustainability (CES), University of Surrey.  Kok Siew is a chemical engineer by training with >10 years of research and industrial consultancy experience in systems engineering, process integration, techno-economic analysis and environmental life cycle assessment (LCA). His research vision is to develop novel and sustainable solutions from a systems engineering perspective, to facilitate the transition of the chemical, energy and waste industries from a fossil-based, linear system to one that is fundamentally sustainable by using renewables as the mainstream resources and by fully embracing circular economy principles. He has contributed to more than 10 UK and international projects funded by NERC, Innovate UK, EU FP7, Royal Academy of Engineering and Newton Fund. His research is significant in terms of addressing global challenges in the 21st century, aligned with the UN SDG 7 and 12, the UK Industrial Strategy, and international ambitions to achieving circular economy and net-zero target. Kok Siew has published more than 30 articles including journals, book chapters and magazine article, and have co-authored an advanced textbook “Biorefineries and Chemical Processes: Design, Integration and Sustainability Analysis”. His work related to decarbonisation of energy systems has been recognised by the IChemE Junior Moulton Medal award (best publication) in 2011. Furthermore, Kok Siew has been nominated for the University of Oxford Vice-Chancellor's Environmental Sustainability Staff Award in 2022 for his contribution in actively promoting environmental sustainability through his research vision, which develops sustainable solutions from a systems engineering perspective. He is an Editorial Board Member of Resources, Conservation & Recycling Advances (RCR Advances) journal and also a reviewer for French ANR and UKRI/EPSRC proposals. Kok Siew is enthusiastic in establishing international collaboration with researchers from multidisciplinary background. He has been working closely with international academic and industrial organisations in the UK, Europe, China and South East Asia. He has organised and participated in a number of British Council/Newton Fund workshops in Malaysia, Mexico, Brazil, Kazakhstan and China, and attended the Royal Academy of Engineering Frontiers of Engineering for Development Symposium “From feeding people to nourishing people”. He has a long-term ambition in influencing resources and waste management practices in developing countries towards sustainable development through cross-disciplinary and cross-sectoral collaboration between the UK and international organisations. His ambition in international development together with the objectives of SYNERGORS are well aligned with the UK Industrial Strategy in enhancing resource efficiency and mitigating pollution and waste materials, while achieving a sustainable industrial growth and a more resilient economy at global level. Awards and Achievements -
  • Nominated for the University of Oxford Vice-Chancellor's Environmental Sustainability Staff Award, 2022.
  • Best Oral Presentation Award, Newton-Al-Farabi UK-Kazakhstan workshop “Low-carbon Future: Efficient Management of Resources and Energy”, 26-28 September 2016, Astana, Kazakhstan.
  • IChemE Junior Moulton Medal for the best publication, 2011 - “Ng, K.S., Lopez, Y., Campbell, G.M., Sadhukhan, J., 2010. Heat integration and analysis of decarbonised IGCC sites. Chem Eng Res Des., 88 (2): 170-188.”
  • PhD Scholarships (2008-2011): Overseas Research Scholarship (ORS), Manchester Alumni Funds, Process Integration Research Consortium (PIRC) Research Funds, School of Chemical Engineering and Analytical Science Scholarship
  • MEng Chemical Engineering with Chemistry Specialist Subject Course Prize (ranked 1st in the cohort), 2008, The University of Manchester.