 A study conducted by PricewaterhouseCoopers and commissioned by the major cork manufacturer Amorim concluded that cork is the most environmentally responsible stopper, in a one-year life cycle analysis comparison with plastic stoppers and aluminum screw caps.While many synthetic corks can be at home, natural corks can either be composted or recycled at specific stores.Companies partner with stores to accept used corks and recycle them into other products; ReCork is the largest of these companies in the United States.