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Field of Dreams

Corn-based plastics have reached the big leagues

Field of Corn

Corn on the cob. Corn nibblets. Corn muffins. Corndogs. And now, corn containers. When the world’s largest retailer recently announced it is switching from petroleum-based plastic containers to those made of corn for its cut fruit, herbs, strawberries, and Brussels sprouts, it signaled that this new generation of plastic had reached the big time.

The environmental benefits of the new containers are expected to be huge: saving the equivalent of 800,000 gallons of gasoline and eliminating more than 11 million pounds of emissions. In addition, the process of extracting the building blocks of plastic from crude oil involves some highly toxic compounds. Not so with corn.

The new plastic is also easier to trash. Because of its natural makeup, this “bioplastic” is biodegradable. It breaks down naturally and can even be composted. This is all good news for our landfills, where containers and packaging account for about one-third of municipal solid waste by weight.

Brewing Plastics
The idea of harvesting plastics from corn has been around for more than six decades, according to Dr. John Dorgan, a chemical engineering professor at the Colorado School of Mines (CSM) in Golden, Colorado.

In the late 1990s, Dorgan and fellow CSM Professor Dan Knauss received a grant from the Technology for a Sustainable Environment (TSE) program. Part of the U.S. Environmental Protection Agency’s (EPA) Science to Achieve Results (STAR) research program, TSE is a joint effort by the EPA and the National Science Foundation to support research and engineering projects in environmentally friendly “green” chemistry.

“EPA’s support allowed me to populate the technical literature with data showing how corn-based plastics compare to petroleum-based plastics. This scientific, apples-to-apples comparison enabled plastics users to replace petroleum-based materials with plant-based materials” Dorgan explains.

Dorgan and Knauss synthesized and studied research-grade PLA, or polyactic acids, which can be harvested from corn. PLAs have the high molecular weight and other physical characteristics needed to make plastics.

Turning corn into PLA is a multi-step process that starts with milling the kernels to remove starch and produce a natural sugar. Then, as in a brewery, that sugar is fermented into lactic acid (the same chemical that makes your muscles ache from overdoing it at the gym). Finally, molecules of lactic acid are linked together in long chains to form PLA.

The EPA-sponsored team focused on making PLA production more attractive to industry. They created and studied specially-synthesized, research grade PLA polymers, and worked to learn how to standardize production and quality control and quality assurance methods. Continuing under EPA support, the CSM researchers are now working to improve the properties of PLA using new advances in nanotechnology to make the first ever polymeric nanocomposites based on 100% renewable resources.

Living the Dream
As the technology advances, some big, exciting questions are on the horizon. Will “bio-refineries” begin to replace oil refineries? Will the Corn Belt of the future bring us as many raw materials for plastic and other products as we now get from imported oil? Now that corn-based plastics have moved into the market place, that future is clearly not just a pipe dream.

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