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Eco-friendly CDs

Sanyo turns to corn for a greener optical disc

Sanyo has developed an optical disc based on a polymer derived from corn which, it says, is as sturdy as current plastic discs but will biodegrade when disposed of.

The company, which is labelling the technology a world first, will begin selling its MildDisc in December. It is initially targeting volume customers producing prerecorded compact discs such as music CDs, VideoCDs or CD-ROMs, said Ryan Watson, spokesman for Sanyo.

The discs have been designed to tackle a problem common to many plastics upon disposal. If burned, toxic gases can be released into the atmosphere causing health and global warming concerns. But if buried they don't break down, which is a potential problem for future generations.

The MildDisc will degrade after a period of about 50 years to 100 years and break down into water and carbon dioxide, Watson said. This timespan means users don't have to worry about losing information during the lifetime of the discs, he said.

The production process begins when US company Cargill Dow, based in the farming state of Nebraska in the US, converts the corn into a polylactic acid. This is done by milling the corn to separate out the starch and then processing the starch to get unrefined dextrose. Using a fermentation process similar to that of beer production, the dextrose is transformed into lactic acid.

Next the acid is converted into a polymer to form the base of the optical disc by Sanyo in a process the company developed with Japan's Mitsui Chemicals and for which the companies have applied for patents, Watson said.

Sanyo estimates that around 85 corn kernels, each weighing an average of 0.5g, are needed to produce enough polymer for a single 12cm optical disc, so an average ear of corn can produce around 10 discs.

The International Recording Media Association estimates world demand for CDs at around nine billion annually and the US Department of Agriculture calculates world corn production at about 600 million tons, so making enough polymer to satisfy the demand for discs would require less than 0.1 percent of the world's corn production.

Initially the company will focus on discs for prerecorded applications although it is considering recordable and rewritable versions of the MildDisc. DVDs based on the same technology are also a future possibility, according to Watson.

When sales begin at the end of this year, the disc blanks will sell in bulk for roughly three times the price of current plastic discs. However, Sanyo estimates it will be able to reduce this premium to around 1.2 times as much as production ramps up and volume shipments begin.

Cargill Dow is using the same initial process and its own refining process to produce its NatureWorks polymer film. Several companies are using the film to make a range of goods including cartons, candy wrappers, kitchen utensils and acrylic sheets and fabrics


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