The circular economy (CE) and its emergent application to the built environment has been progressively discussed in industry, academia, and government spheres. However, the intrinsic complexity of CE practices and the distinct characteristics of the construction industry pose considerable challenges to CE implementation. Digital tools are increasingly recognized as a viable solution to overcome these challenges, but there remains a notable gap in understanding the extent to which digital tools can facilitate the transition to CE in the built environment, especially within the context of broader decision-making. This study investigates how current research elucidates the role of digital tools in facilitating CE practices, and in what specific ways these tools can effectively enable circularity in the built environment. We provide a comprehensive overview of state-of-the-art approaches for enabling circularity in the built environment with digital tools, and identify the challenges, gaps, potentials, and future themes that are occurring in the current literature. Based on the literature review, we developed a framework that identifies and maps ten prominent digital tools: BIM, GIS, AI & ML, IoT, blockchain, digital twin, AR & VR, digital platform/marketplace, and material bank/database. The proposed framework integrates life cycle assessment stages for buildings and building products with key CE principles and the role of each digital tool in enabling CE in the built environment. Our findings indicate that, despite the considerable focus on Building Information Modeling (BIM) and Geographic Information Systems (GIS), technologies such as the Internet of Things (IoT), big data, and blockchain, while promising, have not seen widespread adoption by industry practitioners. Key challenges identified include the need for continuous updates to GIS and BIM models, uncertainties due to unreliable data, difficulties in data management and accessibility, and limited integration of digital tools in construction. To address these challenges, our framework proposes six strategies: (1) Tracking: Systematic tracing of material flow throughout the life cycle, (2) Reducing: Minimizing resource use and environmental impact through optimized production and design, (3) Collecting: Gathering and storing data from existing building stocks in a digital format, (4) Circulating: Effective end-of-life management through reuse, recycling, and waste management, (5) Maintaining: Regular product maintenance and data updating, and (6) Improving: Promoting biodiversity, environmental conditions, and societal well-being. This study contributes to the body of knowledge by highlighting the use of digital tools in advancing CE practices, and offering valuable insights for researchers, practitioners, and policymakers committed to sustainable development across industries.

Macro energy system optimization models are important tools for understanding the possible outcomes of deep decarbonization pathways and can inform the impacts of policy mechanisms that aim to reach net-zero greenhouse gas emissions by mid-century. Given that current U.S. federal climate policy is insufficient to achieve carbon neutrality, state-level decarbonization efforts are of increasing importance. In this research, we use a comprehensive energy systems model (Temoa) to explore the implications of achieving decarbonization goals through either federal or state action. We consider two carbon budget policy scenarios: (1) 23 climate-friendly states set net-zero carbon dioxide emissions targets by 2050; (2) a federal policy that matches the greenhouse gas emissions levels of the state-policy, but with the added flexibility of this being a national constraint. Both scenarios achieve a carbon dioxide emissions reduction of approximately 40% by 2050, but the spatial distribution of emissions limits varies by scenario. Because our approach endogenizes end use technology choice, through this investigation, we demonstrate that state-driven net-zero carbon pathways select a substantially different least-cost set of technologies relative to the federal policy. Specifically, through state-level climate policy, we see a roughly 17% increase in electricity generation by 2050 as compared to a federally-led scenario, indicating an expansion of the electric sector’s role in decentralized decarbonizations. Of this electric sector expansion, the Northeast accounts for nearly 62% of generation increases by 2050. Additional increased technology deployments within the state-led scenario include direct air capture systems in the California and Northeastern regions while, conversely, the federally-led decarbonization scenario relies heavily on the utilization of bioenergy with carbon capture and storage (BECCS) systems in the Southeast. Further, traditional fuel use increased within the federal scenario’s transport sector. This study offers new understanding of the risks associated with technology lock-in under different decarbonization pathways, highlighting the importance of early planning for long-term action.

Life cycle assessment is a valuable tool used to assess the environmental impacts of a given product or process. Standard attributional life cycle assessment methodology focuses on a set of direct environmental impacts resulting from a given production process or system and often focuses on the global warming potential quantified by the release of greenhouse gasses from the system. While the standard approach can provide a valuable means of comparing a variety of environmental impacts from individual technologies or entire systems, standard practices focus on emissions to air, water, and soil. Studies following this framework fail to quantify stresses to the global supply of food, water, and energy imposed by arable land use, freshwater use, energy consumption, and changes to human well-being, biodiversity, and the global climate system. Ignoring these indirect impacts can lead to incomplete conclusions from life cycle assessment studies by missing disproportionate shifts in the water-energy-food nexus which carry significant economic, social, and environmental implications. This work presents a conceptual framework for quantifying stresses induced by engineered climate solutions on local and global suppliers of food, water, and energy. This framework presents a new results metric, the water-energy-food index (WEF index), to evaluate the sustainability of climate solutions while considering the synergies, trade-offs, and conflicts of these important resource sectors.

(1) Background

The United States healthcare industry is the second largest industry contributor to landfill waste worldwide [1]. The healthcare sector is also responsible for as much as 4.6% of greenhouse gas (GHG) emissions worldwide, with emissions continuing to rise [2 ]. These emissions not only contribute to climate change and negative environmental impacts, but also threaten human health. Communities are directly impacted by the health concerns associated with waste processing, harmful emissions, and pollutants associated with the production of healthcare products. Reducing the amount of healthcare products that end up in landfills could greatly reduce these negative impacts.

Moving from single use to reusable medical devices has been identified as a priority and high-impact intervention in healthcare [3]. Thus, we conducted a comparative life cycle assessment (LCA) study of disposable versus reusable stethoscopes. This research was conducted at UPMC’s Children’s Hospital of Pittsburgh (CHP). Disposable stethoscopes are sometimes used instead of reusable stethoscopes to prevent cross-contamination between patients. A research team at CHP was exploring the option of reducing disposable stethoscopes, and the results from this LCA will be used to aid in decision-making at CHP and other hospitals and physicians.

(2) Methods

The cradle-to-gate system boundary included raw material extraction and the manufacturing phase. The functional unit includes one year at CHP’s emergency department and the equivalent disposable stethoscopes (20,000) and reusable stethoscopes (1/7th the lifespan). Foreground data for the disposable stethoscopes was collected by disassembling, weighing, and inventorying the materials of in the disposable stethoscope used at CHP. For the reusable stethoscope, the material composition and weights were derived from prior literature [4]. We used Ecoinvent version 3.8 and TRACI 2.1 V1.05. [5]. These impacts were then scaled to the functional unit of 1 year of use. The impact categories included: ozone depletion, global warming, smog, acidification, eutrophication, carcinogenics, non carcinogenics, respiratory effects, ecotoxicity, and fossil fuel depletion.

(3) Preliminary Results

For every category, the impacts of the reusable stethoscope are less than 0.005% of the impacts of the disposable stethoscopes over 1 year of use. The most significant material contributors were brass in the disposable stethoscope and steel in the reusable stethoscope. These materials also were the largest contributors to the weight of their respective stethoscopes. Switching from disposable to reusable stethoscopes at CHP for 1 year would save 5,783 kg CO2-equivalent.

References:

[1] American Medical Association. (2022, October 11). U.S. health system must come to terms with its environmental impact. American Medical Association. https://www.ama-assn.org/delivering-care/public-health/us-health-system-must-come-terms-its-environmental-impact

[2] Eckelman, M. J., Huang, K., Lagasse, R., Senay, E., Dubrow, R., & Sherman, J. D. (2020). Health Care Pollution And Public Health Damage In The United States: An Update. Health Affairs, 39(12), 2071–2079. https://doi.org/10.1377/hlthaff.2020.01247

[3] Keil, M., Viere, T., Helms, K., & Rogowski, W. (2023). The impact of switching from single-use to reusable healthcare products: a transparency checklist and systematic review of life-cycle assessments. European journal of public health, 33(1), 56–63. https://doi.org/10.1093/eurpub/ckac174.

[4] Chow, K., Divone, J., Leung, K., & Sunday, C. (2012, February 25). Stethoscope—DDL Wiki. Stethoscope. https://wiki.ece.cmu.edu/ddl/index.php/stethoscope

[5] Bare, J. (2011). TRACI 2.0: The tool for the reduction and assessment of chemical and other environmental impacts 2.0. Clean Technologies and Environmental Policy, 13(5), 687–696. https://doi.org/10.1007/s10098-010-0338-9