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Foundry Daily News

12. November 2007

Plastic bags may help recycle steel

That evergrowing pile of plastic bags under the kitchen sink, could be used to recycle steel, thanks to some clever Australian technology.

Steelmaker OneSteel has signed an agreement with the University of NSW that will see waste plastic replace up to 30 per cent of the coke and coal used in their steelmaking process.

Like coke, polyethylene plastic contains carbon, which is an essential raw material used in electric arc furnace (EAF) steelmaking.

EAF is used to recycle steel from scrap metal and accounts for 40 per cent of the world's steel production, which is around 1.1 billion tonnes globally.

The technology, which won the 2005 Eureka Prize for scientific research, has been tested for the past two years at OneSteel's Sydney plant in Rooty Hill.

The results showed a boost in productivity, cut power bills, reduced greenhouse gas emissions and diverted significant volumes of plastic from landfill dumps.

"Plastic is simply another form of carbon," UNSW materials scientist Professor Veena Sahajwalla said.

"In making steel there's essentially no difference between the polyethylene plastic in shopping bags, soft packaging and some drink containers, and a natural resource like coal."

During the EAF steelmaking process, carbon is added to scrap metal and heated to around 1,600 degree celsius.

As the scrap metal melts, a layer of gaseous slag foam forms on top of the molten steel. This ensures the heat remains in the molten mix, rather than radiating into the furnace walls, reducing the amount of energy and time needed to complete the process.

"We are pleased with the trial results of the technology and we see it as an environmental win-win," OneSteel Rod and Bar Division commercial manager, Adrian Howard, said.

According to Mr Howard, the use of plastic in the process doesn't result in toxic fumes escaping into the atmosphere.

"The nasties tend to combust at such high temperatures and disappear," Mr Howard said.

"We have also conducted extensive environmental testing and the results have been very good."

According to Clean Up Australia, four billion plastic bags are used in the country each year, with approximately 90 per cent ending up in landfill. The use of the "green" EAF process will hopefully see a significant percentage of that head instead to the steelworks.

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