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Recycling breakthrough to manufacture green aluminium

A recycling breakthrough at UNSW Sydney offers new possibilities for the re-purposing of polymer-laminated aluminium products, such as  coffee pods and post-consumer food packaging.

Previously, recycling of these materials has been inhibited by difficulties separating the materials resulting in excessive material loss and lack of control during smelting. New Thermal Disengagement Technology, described in scientific publications Springer Nature and the Journal of Cleaner Production, offers an innovative, efficient and sustainable microrecycling technique to separate the materials in complex waste.

Thermal Disengagement Technology (TDT) uses heating at specific temperatures to breakdown and separate complex materials. The team found the 550°C was the ideal temperature to destroy the plastics within the polymer laminated materials without damaging the aluminium resulting in the recovery of high quality aluminium with zero metal loss. The entire process only takes 20 minutes.

The researchers managed to achieve 96-99 per cent purity in the recovered aluminium making it cost effective for industrial production. Along with the increased purity, and low oxidation, the method does away with the need for secondary smelting and results in less metal loss than other aluminium recycling techniques.

Scanning electron microscopy at Microscopy Australia’s UNSW Sydney facility, the Electron Microscope Unit, was used to compare the structure of the aluminium prepared using different TDT techniques. Very thin samples were made using a focused ion beam so the resulting microstructure could be observed using a transmission electron microscope.

This research compliments Prof. Sahajwalla’s previous ‘Green Steel’ technology developed using Microscopy Australia’s UNSW Sydney facility. “We developed Green Steel technology where we extract hydrogen and carbon [for coking] from old rubber tyres as an innovative and green pathway in steelmaking, and we now can develop new ‘Green Aluminium’ with our novel technique called Thermal Disengagement Technology,” said Prof. Sahajwalla, whose SMaRT Centre is part of UNSW’s Faculty of Science. Microscopy Australia’s UNSW Sydney facility also played a large role in the development of the ‘Green Steel’ technology.

Prof. Sahajwalla said: “Green Steel and green manufacturing are capabilities we have been pioneering for over a decade. The jobs and sustainability revolution our government wants to create as announced in its 2020 budget can get a boost from some of these sort of existing innovations where industry and researchers are already successfully partnering.

“Using waste-reforming technology can create new supply chains and jobs, especially in regional locations, because it doesn’t have to be large scale nor expensive. That is why I see a future where recycling and manufacturing are aligned, where waste and recycling become part of the manufacturing supply chain, and that is important in this new COVID era where we now highly value ‘sovereign capability’.”