Researchers have developed a clean, cost-effective way of upcycling used plastic to turn it into valuable nanomaterials and high-quality fuel.
Important points
- New technology produces carbon nanotubes and cleans liquid fuel from used plastic
- Intelligent solution for the simultaneous upcycling of plastic and agricultural waste
- Circular economy approach to turn two massive waste streams into real revenue
Worldwide only around 20% of plastic waste is recycled. Increasing that number remains a challenge, as recycling plastic cleanly can be expensive and typically yields inferior products, often making it financially unprofitable.
The new method developed by researchers at RMIT University can make high-quality plastic products – carbon nanotubes and clean liquid fuel – while recycling agricultural and organic waste.
The team’s two-step process, published in the Journal of Environmental Management, converts organic waste into a high-carbon, high-quality form of charcoal and then uses that as a catalyst for upcycling the plastic.
Lead researcher, Associate Professor Kalpit Shah, said upcycling two massive waste streams through a circular economy approach could bring significant financial and environmental benefits.
“Our method is clean, inexpensive, and easily scalable,” said Shah.
“It is a clever solution for processing both used plastic and organic waste – whether tons of biomass from a farm or food waste and garden clippings from the green household bin.
“We hope that in the future this technology can be used by municipalities and local governments to turn this waste into real revenue streams.
“With Australia banning the export of plastic waste from next year, it is important that we explore sustainable and cost-effective alternatives beyond recycling.
“Upcycling plastic with local technology would allow us to get the most value from our limited resources and bring us closer to a true circular economy.”
Unfantastic plastic
The export of unprocessed single resin / polymer plastics will be banned from July 1, 2022 under new Australian laws phasing out the export of waste plastic, paper, glass and tires.
Australia’s national recycling target calls for 70% of the country’s plastic packaging to be recycled or composted by 2025, but a recent report found that only 9.4% of plastic was recycled between 2017 and 2018.
Recycling and clean energy is one of six national priorities in the Federal Government’s Modern Production Strategy.
High quality nanomaterials
The new plastic upcycling approach offers a sustainable alternative to the production of carbon nanotubes (CNTs).
These hollow, cylindrical structures have exceptional electronic and mechanical properties with applications in a variety of sectors including hydrogen storage, composites, electronics, fuel cells, and biomedical technologies.
There is increasing demand for carbon nanotubes, particularly in the aerospace and defense sectors, where they can facilitate the design of lightweight components. The global market for CNTs is projected to reach $ 5.8 billion by 2027.
From old to new
The new method begins by converting agricultural or organic waste into biochar – a carbon-rich form of charcoal that is widely used to improve soil health.
The biochar is used to remove toxic impurities – such as polycyclic aromatic hydrocarbons known as PAHs – while the waste plastic is broken down into its constituent parts gas and oil.
The process removes these contaminants and converts plastics into high quality liquid fuel.
At the same time, the carbon in the plastic is converted into carbon nanotubes that encase the biochar.
These nanotubes can be exfoliated for use in various industries, or the nano-reinforced biochar can be used directly for environmental remediation and agricultural land upgrading.
The study is the first to use inexpensive and widely available biochar as a catalyst for the production of pollution-free fuels and carbon nanomaterials from plastic.
Shah, the assistant director (academic) of the ARC Training Center for Transformation of Australia’s Biosolids Resource at RMIT, said that while the study only looked at one type of plastic, the approach would be applicable to a range of plastic types.
“We focused on polypropylene because it is widely used in the packaging industry,” he said.
“We need to do more research to test different plastics as the quality of the fuel produced will vary, but the method we developed is generally suitable for upcycling polymers – the basic components of all plastics.”
Hyper efficient reactor
The laboratory-scale experimental study can also be replicated in a novel hyper-efficient reactor developed and patented by RMIT.
The reactor is based on fluidized bed technology and offers a significant improvement in heat and mass transfer to reduce total capital and operating costs.
The next steps for the upcycling research will include detailed computer modeling to optimize the methodology, followed by pilot tests in the reactor.
The RMIT School of Engineering team is committed to working with the plastics and waste industries to advance research and explore other potential applications of the upcycling method.
The research was supported by a DECRA grant from the Australian Research Council.
“Conversion of pyrolytic non-condensable gases from polypropylene copolymer into bamboo-like carbon nanotubes and high-quality oil using biochar as a catalyst”, with the RMIT co-authors Dr. Savankumar Patel, Pobitra Halder, Dr. Sazal Kundu, Mojtaba Hedayati Marzbali, Ibrahim Gbolahan Hakeem, Dr. Biplob Kumar Pramanik, Dr. Ken Chiang and Tejas Patel are published in the Journal of Environmental Management (DOI: 10.1016 / j.jenvman.2021.113791).
/ Public release. This material is from the original organization (s) and may be of a sporadic nature that has been edited for clarity, style and length. The views and opinions expressed are those of the author (s).
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