Yogurt producer Stonyfield Farms, Montpelier, Vt., has switched to polylactic acid (PLA) for many of its thermoformed containers. Stonyfield announced this week that it will use PLA for its Yo Baby and other products that had been packaged in polystyrene. This is believed to be the first use of PLA for yogurt. The company’s initiative is unusually far-reaching: Not only did it do a comprehensive lifecycle analysis of all the alternatives, it reached all the way back to the farm. As part of the initiative, Stonyfield will pay farmers to grow corn that has not been genetically modified, although the company admits that it would be impossible to keep genetically modified corn out of the cup feedstock.