Pathways to the Circular City: Scenario Planning and Agent-Based Modeling to Explore Developer Decision-Making and City Policies

This article presents a novel use case of the deployment of agent-based modeling (ABM) to explore developers’ decision-making along a spectrum of reuse in the built environment. This research project used ABM to model multiple pathways to realizing circularity at the community scale through the reuse of existing buildings and adoption of deconstruction as alternatives to demolition in Ithaca, New York. This exploratory analysis demonstrates (1) the use of ABM in scenario planning, (2) the use of ABM to assess how preservation and building material reuse options affect city-wide greenhouse gas emissions in the form of embodied carbon, (3) and the potential to use the model results in policy analysis. The results of the analysis emphasize trade-offs in local government policies. A Business As Usual scenario produces the most CO2 emissions and the highest total dollars invested and total square footage developed. This is in contrast to the other three scenarios. A Maximize Preservation scenario achieves the lowest total embodied carbon emissions through retention of existing buildings while maintaining the second highest total investment in urban development. The Deconstruction Incentive and Mandatory Material Reuse scenarios, which involve incentivizing building material reuse, lead to strong ROI signals for developers, reducing the search for suitable properties for new construction as deconstruction becomes a viable avenue for generating returns. ABM-generated scenarios exhibit differences in the performance of developers according to their type and scale. This research produced a readily available ABM and graphical interface that could be used by researchers and local government agencies exploring pathways to achieving circular cities through policies that can affect urban development processes and embodied carbon emissions.