The technical or biological loop? Economic and environmental performance of circular building components

The construction sector can become more sustainable by applying the Circular Economy concept, which distinguishes two main pathways: substituting materials for biological materials, or optimizing the use or reuse of technical materials. Practitioners sometimes choose one pathway over the other, but knowledge of which of these pathways yields the best circular performance for the building industry is lacking. To determine which pathway is the most circular, the performance of biological, technical, and hybrid variants for a circular kitchen and renovation façade are developed and compared with one another and with the linear ‘business-as-usual’ (BAU) practice components. The novel methods of Circular Economy Life Cycle Assessment (CE-LCA) and Circular Economy Life Cycle Costing (CE-LCC), and traditional material flow analysis (MFA) are used. The results show that the biological kitchen and façade consistently perform best in the CE-LCA, but perform second best and worst in the MFA respectively, and consistently perform the worst in the CE-LCC. Technical solutions perform best in the MFA. However, while the technical kitchen performs second best in the CE-LCA and best in the CE-LCC, the technical façade performs worst in the CE-LCA and third best in the CE-LCC. A purposeful, reversible, hybrid application of biological and technical materials yields the most consistent circular performance overall, performing best in the CE-LCC (saving 17 % compared to BAU), second best in the MFA (saving 23 % compared to BAU), and third best in the CE-LCA (an increase of 21 % compared to the BAU). This study shows that neither a purely biological nor purely technical solution performs best overall, but that a purposeful hybrid solution can mitigate the disadvantages of both pathways. Further research is recommended to assess more building components and other hybrid variants.