Circular Economy in Heat Supply Systems for Buildings: An Overview of the End of Life of System Components and Existing Evaluation Systems and Products

Abstract In order to achieve climate protection targets, many heating systems must be converted to renewable energies and more efficient systems. Most of residential buildings in Germany are heated with natural gas (50 %), 25 % with an oil. Around 45 % of the heating systems are older than 15 years, 20,5 % are even older than 25 years. Therefore, a high replacement rate is to be expected in the next few years. In the context of circular economy, the accumulating materials should remain in the material cycle. Some materials, such as metals, can be recycled easily. However, building services engineering, in particular heat supply, has become increasingly complex. This paper focuses on the state of the circular economy of heat supply systems for buildings. Firstly, a detailed examination of products utilized in heat supply systems is undertaken. Secondly, an assessment of the end-of-life scenarios for these components was conducted, considering disposal routes and recycling rates. Lastly, an evaluation of assessment systems fostering a circular economy regarding heat supply systems is performed. The aim of the work is to provide an overview of the state of the art with regard to circular economy in heat supply and thereby draw conclusions as to where potentials and obstacles exist.