RALEIGH -- New plastics designed to break down naturally have been hailed as environmentally friendly alternatives to traditional plastics. Instead of taking decades or even centuries to decompose, they vanish in a few years.

But new research at N.C. State University suggests they may not be so green after all.

The study, led by NCSU doctoral student James Levis, found that biodegradable plastics can release large amounts of methane gas when they break down in landfills. Methane is one of the most problematic greenhouse gases, able to trap much more heat than carbon dioxide, making it a major contributor to global warming. It's also flammable.

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