Wednesday, August 10, 2005

Australian scientists use plastic to make steel

By Paul Tait

SYDNEY (Reuters) - Australian scientists have developed a technique to use waste plastic in steel making, a process that could have implications for recycling scrap metal that accounts for 40 percent of steel production.

Professor Veena Sahajwalla of the University of New South Wales has won a prestigious Australian science award for what she calls "the hottest research in town," which she hopes will turn an environmental headache into a valuable resource.

Under the process, waste plastics are fed into electric steel-making furnaces as an alternative source of carbon and heated to super-hot temperatures of 1,600 degrees Celsius (2,912 Fahrenheit).

Sahajwalla said many waste plastics, from shopping bags to dishwashing liquid containers and drink bottles, contain high enough levels of carbon to be useful in steelmaking.

Carbon is used to add strength to steel. The higher the carbon content, the stronger but less ductile it is.

"What happens in a steelmaking furnace is that we are melting scrap steel, you can imagine if you've got your old cars and washing machines and so on," Sahajwalla told Reuters.

"The carbon component that's present inside plastic is what we're after and, at those high temperatures, we're able to react it in a way that we're able to use that carbon that's locked in the plastics. Typically you would add coal and coke," she said. Clyde Henderson, of coal industry newsletter Energy Economics, said similar technology using pellets of recycled plastic had been used in firing power stations in Japan. "I guess it's probably going to be, in terms of proportion of feed for these kinds of plants, a relatively minor kind of thing," Henderson told Reuters.

"I don't think the coal industry would see it as a threat. It's more an environmental angle, I think," he said.

Sahajwalla said her process did not replace all of the coal and coke, but still used a mix of plastic and coal.

Australia is the world's top coal exporter, shipping 122 million tonnes of metallurgical grade coal worth $9 billion ($6.8 billion) last year.

Australians use roughly a million tonnes of plastics a year, much of which ends up as waste destined for landfills.

"If you've got a whole lot of waste plastics that end up in landfill, not just in Australia but across the world, then it's really coming up with alternative technology for its disposal which is environmentally friendly," Sahajwalla said.

Sahajwalla, from the university's School of Materials Science and Engineering, won one of the Australian Museum's Eureka prizes for achievements in science for her work on Tuesday and said she was in talks about industrial applications for her project.

She said PVC was one of few plastics not suitable for the process because of potentially carcinogenic emissions when burned. ($1=A$1.32)

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