Stonyfield's new cup ??? now being used in its multipack Yo-Baby products and a few others ??? replaces polystyrene with a plant-based plastic called polylactic acid, or PLA. Essentially, it is a plastic made from corn.The PLA is made by NatureWorks in Nebraska, which is owned by Cargill, then sent to Clear Lam Packaging in Illinois, where it is mixed with colorings and other additives and turned i