The circular economy. It is difficult to determine where it starts and where it ends. We could imagine a 3D journey in which a circle becomes a spiral and the third axis is represented by the second law of thermodynamics, the one about the irreversibility of physical processes without adding energy. If this was the case, linear economy advocates could be right. They claim that a resource must be exploited full stop while enjoying the benefits of this “development” in the short term. But there is a fly in the buttermilk of this theory: solar energy powers the whole renewable energy system and should do so for the next 4 billion years. In practice, it is this energy that we will need to power the circular economy in the near future, without undermining the second law of t...