How a coffee grinder and some old tyres led to the creation of sulphur-free light oil

Monash University

Using a coffee grinder, a freezer and a furnace, researchers have discovered a chemical synergy between scrap tyres and polystyrene can be harnessed to create sulphur-free, light oil.

Scrap tyre chips were frozen with liquid nitrogen and ground using a coffee grinder, blended with plastics and placed in a furnace at 600 ◦C.

Believed to be the first study of its kind, chemical engineers at Monash found strong synergies between tyre scrap and plastics including low-density polyethylene (LDPE) and polystyrene when they were treated together in a system using the process known as rapid pyrolysis that involves subjecting them to high temperatures over a short time.

Blending either polystyrene or LDPE with tyre scrap for pyrolysis effectively eliminated the production of hazardous sulphur-containing compounds that are normally found in the liquid oil produced from the breakdown of tyres.

Professor Lian Zhang, of the Department of Chemical and Biological Engineering, who led the research team, said LDPE and polystyrene are both very commonly used across a range of consumer goods including packaging, plastic bags and films, bottles and containers and even medical disposables.

“Adding these plastics and using this process to break down tyres can substantially reduce the risk of releasing hazardous materials into the environment,” said Professor Zhang.

“We believe our findings provide a very solid foundation and justification for using co-pyrolysis as an effective and value-added technology for upcycling potentially troublesome waste products.”

Further analysis allowed the mechanisms underpinning the interactions between the chemical components in the system to be identified in detail, explained PhD student Wahyu Narulita Dewi, first author of the study just published in the international journal Waste Management.

The Monash team is already undertaking further work to develop and optimise the technology with the aim of enhancing the yield and the quality of the sulphur-free light oil produced by the process.

The research is being supported by Tyre Stewardship Australia, a tyre industry organisation that promotes the development of viable markets for end-of-life tyres.

Further related research will also be a focus of a new Australian Research Council (ARC) Industrial Transformation Research Hub for Value-Added Processing of Underutilised Carbon Waste, led by Professor Zhang, to be launched later in 2024.

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