Hypothesis

Green May Not Be Clean

Plastic made from corn? That has to be better for the Earth than plastic made from petro-chemicals, right? Wrong. While corn-based plastics have been hailed as a major breakthrough in the biological processing of an industrial commodity, one Dartmouth professor decided to take a closer look. Tillman Gerngross of the Thayer School of Engineering studied the process of substituting a corn extract called polyhydroxyalkanoate (PHA) for petroleum polymers used in plastics. He discovered that producing plastics from maize extract is more harmful to the environment than traditional, petroleum-based plastic production. Gerngross analyzed the amount of energy required to plant, fertilize, harvest, clean and ready the corn for plastic production and found, among other things, that the green approach uses 19 times more electricity than the process it was supposed to replace.

Gerngross, a plastics specialist, was surprised and disappointed in the results of his study. But he sees a silver lining in his work. "We now have the tools to look at the environmental impact of biological processes," says the professor. "We expect some processes to fail this analysis, but we anticipate others will demonstrate superior performance. We will be looking for both."