Eco-energy without limits? Federal Laboratory for Materials Testing and Research Dübendorf, St. Gallen und Thun, 11.05.2021 - Even a sustainable circular economy doesn't run without energy. Solar panels and wind farms, tidal and geothermal power plants: They all divert energy from energy fluxes that had remained untapped since time immemorial. The question is therefore: What part of these energy fluxes can mankind use for its own purposes without damaging the Earth's energy system? Empa researchers have developed an approach to estimate this. The Earth has its limits. We are becoming more and more aware of this in view of the climate crisis, the increasing extinction of species and the littering of the oceans (and even space) as a result of human activity. In response, governments and institutions the world over are championing the concept of a circular economy. By closing material cycles, the environmental impacts associated with the extraction of raw materials shall be avoided and the waste problem solved. This approach is, however, not sufficient to build a sustainable society in and by itself, as it leaves the questions open of how much and how quickly materials can be cycled and what energy is used to power these cycles. After all, in a truly sustainable society, not only material flows but also energy flows must remain within the limits set by our home planet.