Carbon-reinforced concrete (CRC) has the potential to play a pivotal role in optimizing the built environment and has therefore been experiencing a wave of research and development in the construction industry in recent years. The production of carbon fibers for CRC is energy-intensive, prompting the need to explore circular economy approaches (e.g., recycling at the End-of-Life (EoL)) to optimize the environmental performance of this material. Underdeveloped processes and a resulting lack of primary data regarding the recycling of CRC have hampered a comprehensive sustainability assessment of the novel composite building material. The novelty of this article is the detailed presentation of possible EoL scenarios for CRC and the detailed determination of the respective environmental impacts. This study aims to model EoL options within a Life Cycle Assessment (LCA), focusing on the EoL stage based on ISO 14040/44 using the GaBi ts 10.5.1.124 software and the CML2001 (2016) methodology. The practical relevance of the study lies in the early consideration of the entire life cycle of new materials, such as CRC, already in the design phase. Furthermore, the EoL can have relevant impacts on the environment, and due to an increasing significance of sustainability aspects, this LCA clarifies first approaches for the future of the construction sector in quantitative statements (e.g., CO₂ emissions). All data are literature-based and are explained in detail and calculated for our case study with the functional unit of one kilogram of re-usable material (reusable and fully usable “raw” material for further use/ development) from a double wall. The impact assessment was calculated for 11 midpoint categories and related indicators, although the main focus was on Global Warming Potential (GWP). It was found that the highest-quality recycled options for CRC arise when the individual fractions (concrete matrix and carbon fibers) are first broken up, separated and then individually processed. This study focused mainly on the processing of the carbon fibers contained in CRC, for which pyrolysis and mechanical recycling have the strongest potential for industrial application. For the demolition and separation of both the concrete and the carbon fiber fractions, the conventional transport from the demolition site to the stationary processing plant proved to be the main driver of the GWP (1.4 × 10⁻³ kg CO₂e). In the subsequent processing of the carbon fibers, pyrolysis showed a higher GWP (9.7 × 10⁻³ kg CO₂e) than mechanical recycling (3.1 × 10⁻⁴ kg CO₂e). In addition, the production of one m³ of concrete (C30/37) was compared to a primary raw material concrete fraction. Concrete can be successfully used as a substitute material for the gravel present in the C30/37 concrete. The use of recycled parts in concrete (originating from the concrete used in carbon-reinforced concrete) as a substitute for primary gravel showed a savings of 6.9 kg CO₂e per m³ of primary concrete, corresponding to a reduction of 22.5%. The results show that the mechanical recycling of carbon fibers is overall the route with the lowest energy input and emissions. However, compared to pyrolysis, the recycled carbon fibers from mechanical recycling have a lower quality. Therefore, despite the higher energy input, pyrolysis is a more promising approach to close the material cycle. Furthermore, recycled aggregate concrete can reduce emissions by a quarter compared to primary concrete. Finally, this work aimed to provide a basis for further life cycle optimization in the construction sector. In subsequent studies, the EoL must be combined with the production and use stages to depict the entire life cycle, identify possible trade-offs and compare the results with conventional construction methods or materials such as steel-reinforced concrete.

The transition to sustainable resource management necessitates frameworks that capture complex interconnections between resource systems and environmental impacts. To identify and evaluate potential benefits, harms and their interconnection during the transition toward a sustainable and resilient energy system, the Resource Nexus Approach systematically considers the interconnections between critical and abundant resources to highlight synergies and trade-offs. This article introduces and proposes the concept of a Resource Nexus Life Cycle Assessment (RN-LCA) methodology, integrating life cycle approaches with the RN framework. I consider the environmental resources biota, climate, material, soil, space, water, as well as the derived resources land, energy, waste, food, and sea, and analyze their roles within LCA. A review of existing literature on LCA and the RN reveals that while LCA is frequently employed in RN studies, its application often overlooks systemic interactions and multidimensional trade-offs. The proposed RN-LCA methodology operationalizes these interconnections by adapting LCI and LCIA methods to quantify and characterize resource flows as well as evaluate resource use alongside environmental impacts and guiding the identification of synergies and trade-offs in the LCA study. Using the transition from lignite based to photovoltaic electricity generation as an example, this study shows how RN LCA enables the assessment of environmental synergies and trade offs in renewable energy transitions.Policy relevance is addressed by embedding metrics for emission targets, starting with planetary boundaries.

Portland cement, the most widely used binder, generates large amounts of unavoidable process-related CO2 emissions that are hard to capture and store. Achieving carbon neutrality in construction therefore requires alternative binders. Alkali-activated binders (AAB) are a key option, but their manufacturability remains challenging. This study synthesised AAB using either basalt with ground granulated blast furnace slag or calcined clay with natural pozzolan. Extrudability was central, since suitable rheology is essential for continuous processes such as fine concrete extrusion and thus for advanced applications. A cradle-to-gate life cycle assessment (LCA) compared the environmental impacts of the AAB to a cement-based fine concrete, using a functional unit based on compressive strength and extrudability. The influence of slag addition and activator concentration on strength development was assessed, as were the effects of activator type and methylcellulose on setting behaviour. Setting was monitored by continuous ultrasonic pulse velocity measurements combined with ball penetration tests to evaluate suitability for extrusion. A low-risk, targeted optimisation method for AAB extrusion was developed. Results show that AAB substantially reduce environmental impacts, especially CO2-equivalents, mainly by avoiding clinker production. Electricity use, activator production, and transport remain hotspots, indicating further savings through renewable energy and supply-chain optimisation in this study.

Biological diversity, or short, biodiversity, is hereby defined as the variety of living organisms, classified as the genetic, species, and ecosystem diversity in terrestrial and aquatic ecosystems. Biodiversity loss is a significant global risk and highlights the importance of understanding its impacts and developing strategies for its preservation by all relevant decision-makers. It introduces the five drivers of biodiversity loss identified by the SCBD and shows that LCA already assesses bits and pieces to consider biodiversity impacts. The need for spatial modelling in LCA is discussed to account for global impacts related to biodiversity. The text suggests potential research areas for LCA, such as sound pressure, odour, and loss of genetic and ecosystem diversity. It mentions the GLAM project, which is working on recommendations for new impact assessment models, and introduces the concept of global extinction probability (GEP) and product biodiversity footprint (PBF) as examples to assess potential biodiversity loss.