Towards zero-waste cities: Insights from building material waste flow mapping and stakeholder engagement in Montréal

Montréal is among numerous cities pursuing zero-waste objectives aligned with global sustainability goals. Construction, renovation, and demolition (CRD) waste represents a significant component of urban waste streams and offers substantial opportunities for reduction through circular economy (CE) strategies and innovative material management approaches. Achieving zero-waste urban resource management requires an integrated understanding of three key dimensions: (1) the characterization of CRD materials, (2) the infrastructure supporting CRD waste management, and (3) stakeholder dynamics within the building sector and their interactions with CRD materials across the life cycle. However, data describing these dimensions remain fragmented, limiting the implementation of CE practices and evidence-based policy and planning decisions. This paper presents Montréal as a critical case study demonstrating how qualitative and quantitative CRD data can be integrated and visualized to create an exploratory data-integration and stakeholder-informed mapping framework for urban resource management. The study combines a literature review, semi-structured interviews, field observations, thematic analysis, and data visualization methods to spatialize and map CRD flows. The objectives are to characterize CRD waste and its spatial distribution, identify key stakeholders and their roles throughout the CRD waste life cycle, and determine challenges and opportunities for policy intervention. Results indicate that Montréal recovers 42% of CRD materials, while the remainder is landfilled. Stakeholder analysis revealed that 65% of interviewees are involved in end-of-life activities, while material classification, intersectoral collaboration, and financial incentives emerged as key challenges influencing CE implementation. Findings highlight the need for coordinated stakeholder engagement and data-driven decision-making to advance towards zero-waste.