Building a circular economy is one of the biggest aims to achieve sustainability and fight climate change. But what if cycles cannot be closed easily? Then it’s time to apply rougher measures and – literally – smash everything to pieces. Some material cycles can be closed relatively easily, and appropriate systems have been in place for years: Glass, steel, but also certain types of plastics as long as they are homogeneous. But what about the giant amounts of municipal waste containing mixed and often soiled plastics?