Research Overture 3 | Circular Future Cities

Key Concepts

• Circular Economy in Construction: Moving from a linear "take-make-dispose" model to a circular model emphasizing reuse, remanufacturing, and recycling of building materials.
• Urban Systemic Perspective: Shifting focus from the building level to the city scale and beyond, considering material flows and interdependencies within the larger settlement system.
• Systemic Circularity: Mapping and analyzing material flows across space and time to identify environmental hotspots and resource needs.
• Input/Output Interface: Understanding and improving resource use and recovery between buildings and the city.
• Information Management: Supporting the flow, quality, and longevity of material data for effective circular economy practices.
• Material Passport: A data carrier that follows a product, containing information about its composition, manufacturing, and life cycle.
• Distributed Circular Data: Utilizing distributed ledger technology (e.g., blockchain) or distributed databases to create immutable records of building assets and facilitate data sharing.
• Mutual Learning Network: Establishing a collaborative environment involving government, industry, and civil society to co-create knowledge for circular future cities.
• Circular Economy Potential Model: Modeling the yield of resources out of buildings using configurational properties to understand how design affects recovery.
• Urban Harvesting: A paradigm of certain, planable, and cyclical recovery of materials from buildings, contrasting with the uncertain "urban mining" approach.

1. The Problem: Waste in the Built Environment

• Globally, an estimated 2.2 billion tons of waste will be generated annually from building deconstruction and demolition by 2025.
• In the United States, construction waste is twice the amount of all residential waste combined.
• This highlights the significant environmental impact of the construction industry and the need for circular economy solutions.

2. The Goal: Circular Economy in Construction at the City Scale

• The project aims to support circular economies in construction at the scale of the city and its surrounding settlement system.
• This involves understanding and supporting material flows between buildings and the urban system.
• The focus is on key enabling technologies at a systemic level and their interdependencies.

3. Three Urban Systemic Perspectives

• The project is structured around three key perspectives:
  • Systemic Circularity: Analyzing material flows and economies in space and time.
  • Input/Output Interface: Examining material flows between buildings and the circular economy.
  • Information Management: Managing information flows, quantities, and qualities systemically.

4. Systemic Circularity: Mapping and Analyzing Material Flows

4.1. System Analysis and Diagnosis (Theme 1)

• Goal: Identify environmental hotspots related to material types and estimate when and where resources are needed.
• Approach: Refine and combine multiple detailed bottom-up models on building energy, material use, and household consumption.
• Methodology: Combine dynamic material flow analysis with life cycle assessment to model supply chains and assess environmental impacts.
• Output: A spatial-temporal mapping of the Swiss building stock and its material resources, serving as a basis for environmental assessments.

4.2. Mapping Material Stocks for Building Types (Theme 5.2)

• Goal: Develop a spatial-temporal mapping and analysis tool for building material stocks based on building types.
• Focus: HDB (public housing) typologies in Singapore, representing a significant portion of the residential housing stock.
• Methodology: Build and calibrate machine learning classification models to infer material quantities from building type and geometry.
• Output: A geospatial tool to explore material stocks in space and time, integrating data from life cycle assessment and material recovery yield models.

5. Input/Output Interface: Improving Resource Use and Recovery

5.1. Design of Improved Materials (Theme 2)

• Goal: Focus on the design of improved materials with less consumption of primary resources and closed material cycles.
• Examples: Concrete with lower CO2 impact, materials that can be reused and remanufactured more easily.
• Approach: Identify non-recycled material flows and linear material flows to optimize new materials in terms of environmental and economic impacts.
• Considerations: Design for disassembly, recyclability, and extended lifespans.
• Output: Definition of information about new materials and mapping of resources for new materials.

5.2. Modeling Material Recovery Yields (Theme 5.1)

• Goal: Model material recovery yields from buildings using configurational properties (how components and materials are assembled).
• Model: Circular Economy Potential Model, evaluating goals and indicators for recovery and reuse.
• Focus: How building components and materials are attached, as this greatly determines how much can be recovered and for what purpose.
• Paradigm Shift: Moving from "urban mining" (uncertain discovery of precious materials) to "urban harvesting" (certain, planable, and cyclical recovery of materials).
• Benefits of Design for Disassembly: Easier maintenance, adaptation, and longer building lifespan.

6. Information Management: Supporting Data Flow and Longevity

6.1. Material Passport Ontology (Theme 3)

• Goal: Improve the idea of material passports as carriers of circular information.
• Approach: Develop a material passport ontology using ontology-based data integration to combine data from multiple sources across the construction life cycle.
• Focus: Relationships between actors, functional classes, data properties, and life cycle phases.
• Building on Existing Ontologies: Building Topology Ontology, work by Souther on agent inactivity and reference.

6.2. Distributed Circular Data (Theme 4)

• Goal: Solve the issue of data longevity by moving towards distributed circular data that can be computationally distributed and carried forward in the long term.
• Original Perspective: Using blockchain to create an immutable record of assets.
• Current Approach: Exploring alternatives to blockchain, such as distributed databases (e.g., interplanetary file system, big chain database) to create a distributed data marketplace.
• Focus: Data organization around a peer-to-peer (P2P) network and the role of the broker in dealing with the distributed data.
• Considerations: Financial incentives for data sharing and the value of circular product data and ownership.

7. Synthesis and Mutual Learning Network (Theme 6)

• Goal: Identify and inform the structures that need transformation to enable circular future cities.
• Approach: Collaboration and engagement between governments, industry, and civil society to co-create knowledge for new institutional structures.
• Considerations: Institutionalized governance structures, norms, and cultural acceptances around privacy and data sharing in different cities.
• Emphasis: Systems-level transition that considers the unique characteristics of each city.

8. Case Studies: Switzerland and Singapore

• The project utilizes case studies in Switzerland and Singapore to explore different contexts and challenges.
• Singapore's leasehold system provides opportunities for planning resource recovery due to the limited lifespan of buildings.
• The differences between the two countries highlight the need to question assumptions and adapt approaches to different settings.

9. Conclusion

• The Circular Future Cities project aims to address the significant waste generated by the construction industry by promoting circular economy principles at the city scale.
• The project utilizes a systemic approach, considering material flows, information management, and stakeholder collaboration.
• The research explores key enabling technologies and their interdependencies, with a focus on creating a more sustainable and resilient built environment.
• The project is still in its early stages, with many open questions and opportunities for further exploration.