Tarragona, España
This paper explores the integration of the Circular Economy within the energy sector, focusing on the European Union’s legislative and policy context. It examines the evolution and definitions of the Circular Economy, highlighting its expansion from waste management to a broader sustainability paradigm. The analysis uses a comparative approach between the theoretical definition of the circular economy and energy efficiency. It emphasizes the biophysical and thermodynamic limits of circularity, particularly the impossibility of creating closed energy loops due to the laws of thermodynamics. The role of energy efficiency emerges as a crucial bridge between circularity and sustainability, with the EU’s “energy efficiency first” principle serving as a key policy tool. The study argues that while material loops can be narrowed, energy flows remain inherently linear, making efficiency measures essential for advancing circular objectives. The relationship between energy efficiency and the Circular Economy is presented as mutually beneficial but asymmetrical, with efficiency being indispensable for circularity’s success.