"Material can follow a circular path, but energy can only add up. One of the challenges is that even "circular economy" needs "linear energy."

“In physics, energy has a very precise definition: it is what characterises something changing in the world surrounding us. Counting energy is therefore nothing else than counting how much the world has changed.”

“If we have a bottleneck on energy, in terms of volume not in terms of price, then we can have a bottleneck on production. And its is probably what has been happening by little steps since 1975. And if we have an additional bottleneck on resources, then we will also get an additional bottleneck on production.”

“When we have replaced human workers by machines, we have gained the fact that we can change the world for 1,000 to 10,000 times less in terms of monetary input. This explains all that has happened to us during the Industrial Revolution. This basically explains all that we have witnessed during the last two centuries.”