This lecture explores the innovative solutions developed by EPFL engineers to tackle the energy transition problem, focusing on renewable resources, circularity, and waste-water-energy integration. It covers topics such as fossil carbon budget, CO2 emissions in Switzerland, energy needs, and learning from nature. The instructor presents case studies on biomass-based fuel production, heat pump integration, and district-level energy management. The lecture also discusses the challenges and opportunities of defossilizing industries through industrial symbiosis and circular economy.