Surplus corn might be used to make plastics that are biodegradable

Surplus crops might be used to replace petrochemicals in a wide array of plastic products, government scientists say. Use of corn starch as a basis for plastics could usher in an era in which discarded manufactured goods would not linger in the environment as trash, but would be biodegradable, in effect disappearing into the soil.

Scientists at the Agriculture Department's Northern Research Center in Peoria, Ill., are attempting to develop a corn starch-based plastic film for use as a mulch, a protective covering that keeps in moisture and heat, for tomatoes and other crops.

``We are working on new formulas for mulches that microorganisms can break down after a crop is harvested,'' says chemist Felix Otey.

No longer would farmers have to remove and burn or bury the mulches. About 125 million pounds of petroleum-based plastic film were produced for mulching in 1985, according to the National Agricultural Plastics Association.

Other uses for corn starch-based plastics, according to a recent article by Ben Hardin in the department magazine Agricultural Research, range from plastic wrap to serving as semipermeable membranes, which could help recover lye used in making rayon. Already starch films produced commercially, as a result of research by Otey and his colleagues, are used as water soluable laundry bags for hospitals.

The depressed price of corn caused by surpluses could make starch film more competitive. As of Sept. 1, the nation had a surplus of 2.5 billion bushels of corn.