Turning plastic bags into steel!
Your plastic shopping bag could one day be turned into steel to make your next car, according to Professor Veena Sahajwalla at the University of NSW.
Instead of being discarded as waste, polyethylene plastic - the type used in shopping bags, soft packaging and some drink containers - potentially can be recycled as both a raw material and a source of energy for making iron and steel, says Professor Sahajwalla.

Professor Sahajwalla is based at the UNSW School of Materials Science and Engineering and she leads the School's Sustainable Materials Processing Program.
"Plastic is just another form of carbon," she says. "When it comes to making iron and steel there's essentially no difference between polyethylene and natural resources such as coal."

Her experiments hold promise of an environmental win-win, significantly cutting the steel industry's use of coal and its production of greenhouse gases, as well as stopping thousands of tonnes of plastic waste from being discarded every year in landfill dumps.
Polyethylene typically is about 15 per cent hydrogen - a potential energy source to fuel blast-furnace processes - and about 85 per cent carbon, roughly the same carbon content as the high-quality coal used for steelmaking.
Under controlled conditions, Professor Sahajwalla experimented with various mixtures of pulverised plastic and coal by injecting them into a furnace.

"By adding plastic into a molten 'melt' at more than 1,500 degrees C we have shown that carbon from plastic can dissolve into iron," she says. "This is exciting because what would otherwise become waste is recycled to become a raw material for this vital industry and it reduces our use of coal in the process. If we want to move along the path to sustainability, this is one way to go."
In 2002, the latest year for which figures are available, Australians used almost 1.2 million tonnes of plastic but recycled only about 13 per cent. Of the resulting one million tonnes of waste, polyethylene accounted for about half.
"If we substituted recycled polyethylene for only five per cent of the coal we use in blast furnaces, that would save about 40,000 tonnes of coal a year. That much coal would make about 80,000 tonnes of iron."
A question mark remains over whether burning polyethylene might release unwanted air pollutants: "We need to do more research on that question, because experience with burning plastics in waste incinerators suggests it may be an issue.
"But incinerators typically operate at about 1,000 degrees C, whereas a blast furnace operates at around 1,500 to 1,600 degrees and is likely to burn the plastic more completely, with fewer troublesome pollutants.
"Polyethylene actually has fewer impurities than coal, such as sulphur and oxides, so there's less of a residue problem after burning it."
Sahajwalla's findings have emerged from her work on other materials used in iron and steel making.
She credits her collaborator in Japan, Professor Masanori Iwasi, of Kyoto University, with having the original idea of using plastic waste as a raw material in blast-furnace ironmaking, but she is extending the technique for the first time into electric-furnace steelmaking, which uses scrap steel to recycle into new materials. Dr Sahajwalla's research is being done in co-operation with BHP Billiton and BlueScope Steel and with support from the Co-operative Research Centre for Coal in Sustainable Development.