It is becoming clear that the post-COVID era will have to be characterized by a paradigm shift in the proposed use of our increasingly limited and valuable resources. The idea of waste, especially in the design field, is gradually taking on new interpretations and, thanks to an ecological and systemic approach, innovative and sustainable. Waste, as natural processes teach us, can be generative sap for something different. The world of design, which as long ago as the 1970s offered a proactive look at the subject, is now in a leading role in the debate on sustainability. The article develops first of all by outlining a theoretical framework of reference that is rooted in the topic of systemic ecology; then presents some cases considered relevant to try to trace a possible way to identify the factor "RE".