The case follows Danish brewer Carlsberg as it develops the Green Fiber Bottle, a beer bottle made of wood pulp, in collaboration with a startup, a small-to-medium sized enterprise (SME), and a Danish University. The case has a dual focus. First, it demonstrates how a company can successfully innovate by leveraging the concept of open innovation. Second, it shows how sustainability - and relatedly, the idea of purpose - can be a powerful motivator to drive open innovation efforts. In this respect, this case serves as one of the first formal documentations of how open innovation can effectively drive innovation activities to address a stated sustainability objective. This co-mingling of sustainability and open innovation has the potential to become a domain in its own right (perhaps under a moniker such as "Sustainable Open Innovation").