New tech could see plastic upcycled into fuel and carbon nanotubes

30 Sep 2021

A magnified image of a carbon nanotube created through the new upcycling method. Image: RMIT University

Researchers at Australia’s RMIT University are trying to develop a cost-effective way to boost the recycling of waste plastics.

A team of Australian scientists has found a way to upcycle used plastic into high-value products such as carbon nanotubes and fuel, while also upcycling organic waste in the process.

The new method converts agricultural and organic waste into a valuable and carbon-rich form of charcoal called biochar, often used for improving soil health.

The biochar is then used in the breakdown of the waste plastic into its components of oil and gas. This process removes contaminants such as polycyclic aromatic hydrocarbons (PAHs) and converts the plastic into high-quality liquid fuel.

Globally, less than 20pc of used plastic is recycled. The process can be expensive and can produce lower-value products.

The new two-step method developed by researchers at the Royal Melbourne Institute of Technology (RMIT) could make the upcycling process financially viable and incentivise investment in something that would have environmental benefits.

‘We hope this technology could be used in future by local councils and municipal governments to help turn this waste into genuine revenue streams’

“Our method is clean, cost-effective and readily scalable,” lead researcher Prof Kalpit Shah said. “It’s a smart solution for transforming both used plastic and organic waste – whether tonnes of biomass from a farm or food waste and garden clippings from household green bins.”

The upcycling process can also use the remaining carbon from the plastic to produce carbon nanotubes – a highly lucrative product in the aerospace and defence industries – to meet demands in a market projected to be worth $100bn by the end of the decade.

“We hope this technology could be used in future by local councils and municipal governments to help turn this waste into genuine revenue streams,” Shah added.

Carbon nanotubes are hollow, cylindrical structures that are known for their mechanical and electronic applications in areas such as hydrogen storage, composite materials, electronics, fuel cells and biomedical tech. They are high in demand in the aviation industry because of their potential use in the manufacture and design of lightweight parts.

In the RMIT study, published in the Journal of Environmental Management, researchers found that the carbon in the plastic could be converted into carbon nanotubes that coat the biochar.

These can then be exfoliated from the material and used in different industries. Alternatively, the carbon nanotube-coated biochar could be used in agriculture to boost soil health and quality.

While Shah said the study only focused on polypropylene – the type of plastic commonly used in the packaging industry – the method could be applied to other forms of plastic waste in the future.

“While we need to do further research to test different plastics, as the quality of the fuel produced will vary, the method we’ve developed is generally suitable for upcycling any polymers – the base ingredients for all plastic.”

The RMIT team will now use computer modelling to optimise the process and conduct trials in a new reactor developed and patented by the university. The team hopes to collaborate with plastic and waste industries to further the research and investigate other potential applications.

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Vish Gain is a journalist with Silicon Republic