Robust monitoring and assessment methods are required to assess circular economy (CE) concepts in terms of their degree of circularity and their contribution to sustainability. This research aimed to develop an integrated framework for the CE context—considering both the technical circularity and the complexity of the three dimensions of sustainability (environment, economy, and social). Two existing methods were identified as an appropriate foundation: CE indicators and life cycle sustainability assessment (LCSA), combining life cycle assessment (LCA), life cycle costing (LCC), and social life cycle assessment (S‐LCA). The developed circular life cycle sustainability assessment (C‐LCSA) framework added circularity assessment (CA) as an additional dimension to LCSA (C‐LCSA = LCA + LCC + S‐LCA + CA). The abundance of CE indicators required a systematic selection process to identify the most appropriate indicators for the framework which was built on criteria levels, performance, loops, unit, dimension, and transversality. The material circularity indicator, product circularity indicator, and longevity indicator were identified as most suited for C‐LCSA. Being developed for a single life cycle, the traditional life cycle approaches needed refinements for application to CE concepts, derived from discussions and proposed adaptions presented in the academic literature. The cut‐off approach was identified as the most suitable end‐of‐life allocation method for C‐LCSA, being in line with the technical system boundaries. C‐LCSA can be used by LCA practitioners to identify trade‐offs between an improved circularity and resulting impacts on the environmental, economic, and social pillars to provide a basis for decision making in industrial ecology.

Purpose: Robust assessments are needed to identify the best circular economy (CE) approaches related to their contribution to achieving a CE by simultaneously considering the complexity of the three pillars of sustainability (environmental, economic, social). In this regard, the circular life cycle sustainability assessment (C-LCSA) framework was recently developed. This study aimed to demonstrate its applicability and capability of identifying trade-offs and interlinkages between the different dimensions using a case study of different CE approaches to carpet tiles. Methods: C-LCSA integrates circularity and life cycle sustainability assessments (LCSA). Thus, this study applied the material circularity indicator (MCI) in parallel to life cycle assessment (LCA), life cycle costing (LCC), and social life cycle assessment (S-LCA). The last technique was applied as social hotspot assessment. Five CE approaches of carpet tiles produced in the US, including strategies like reducing the consumption of primary materials through recycled and bio-based feedstock or replacing carpet tiles for a longer overall service life, as well as recycling, were assessed and compared to their mainly linear counterpart. Results and discussion: The study revealed that recycling carpet tiles containing recycled and bio-based materials at the end-of-life (EoL) resulted in the lowest global warming potential (8.47 kg CO₂ eq.) and the highest circularity (MCI value of 0.76, with 1 indicating the maximum level of circularity) compared to the other scenarios. However, this scenario had a trade-off with a higher acidification potential (0.039 kg SO₂ eq.) and higher costs (US$19.98) compared to the disposal scenario. On the other hand, the scenario using primary, non-bio-based materials in production and disposing of the carpet tiles at their EoL performed the worst in circularity (MCI value of 0.11) and implied high environmental impacts while being more cost-effective (US$10.27). Conclusions: C-LCSA transparently revealed interlinkages in terms of circularity and the overall sustainability performance of different CE approaches. While no significant differences in terms of social hotspots were identified, approaches associated with a higher circularity and improved environmental performance in most impact categories tended to result in higher costs. This emphasized the need for individual and holistic assessments of the new CE approach to identify and address trade-offs. To enhance and foster C-LCSA in academia and industry, further studies applying the framework to different sectors are encouraged.

This study assesses the environmental performance in the end-of-life (EoL) of double walls made of carbon-reinforced concrete (CRC) and steel-reinforced concrete (SRC). The most feasible CRC EoL scenarios are evaluated using life cycle assessment and their environmental performances are then compared to those of SRC. The results showed that mechanical recycling is the best CRC EoL scenario, with a global warming potential (GWP) of 7.0 kg CO₂ eq., while the use of renewable energy can save over 50% of GWP. For SRC, the best scenario was obtained using a mobile recycling plant (GWP of 8.8 kg CO₂ eq.). In general, the further life of the reinforcements is hardly comparable. Steel can be recycled nearly without losses or downcycling, while a closed cycle of carbon fibers is not yet possible. Therefore, carbon fiber properties or EoL processes need to be improved for a closed loop with an optimized environmental performance.