When organic, biodynamic and sustainable vintners look to bring their low-impact philosophies to their packaging, they often end up torn over how to handle closures. Cork is the traditional choice, and it is a renewable material; screw caps, meanwhile, are made from mined metals, and synthetic corks are typically derived from petrochemicals. On the other hand, if consumers discover that a wine has spoiled from cork failure and are forced to throw it away, that's not exactly sustainable either. The answer to this dilemma may lie in the emergent field of bioplastics. Wine Spectator's Dana Nigro explains.