Scenario Based Dynamic Material Flow Analysis of Dutch Macro Infrastructure Stocks: Assessing Future Material Demand and Circularity Potentials

Technical Summary: Scenario Based Dynamic Material Flow Analysis of Dutch Macro Infrastructure Stocks

Problem Statement
Achieving circularity in infrastructure systems requires the effective recovery of secondary raw materials from end-of-life (EoL) stocks to offset future demand for virgin materials. While the Netherlands possesses a well-developed infrastructure stock that is now reaching the end of its designed lifetime (primarily built in the 1960s–1970s), there is a significant research gap regarding the quantification of future secondary material availability from non-building macro-infrastructure. Existing studies often focus on buildings or specific sectors like mobility, overlooking water, utility, and fossil fuel infrastructures. Furthermore, a critical distinction exists between theoretical recovery potential and actual "closed-loop" circularity, where materials retain their original functionality and value. Much of the current recovery in the Netherlands involves downcycling (e.g., concrete aggregates used as road fill), which fails to reduce primary material demand effectively. This study addresses the need to quantify future material demand and the potential for closed-loop circularity for steel, concrete, and asphalt in Dutch macro-infrastructure under diverse transition scenarios.

Methodology
The study employs a stock-based Dynamic Material Flow Analysis (dMFA) model, conceptualized based on the framework by Müller (2006). The analysis covers macro-infrastructure (excluding buildings) across five categories: Highway & railway, Water, Oil & gas, Electricity, and Utility. The three bulk materials analyzed are steel, concrete, and asphalt, which constitute over 90% of the material usage by weight in these sectors.

• Data Sources: Historical stock development, material intensity, and average lifetimes (1950–2023) were collected from the SUBLIME database.
• Lifetime Modeling: A Weibull distribution function was used to model infrastructural lifetime survival curves, as recommended for long-lived assets.
• Scenario Development: Three distinct scenarios were developed to capture future uncertainty:
  • Reference Scenario: Aligns with central projections of asset owners and current trends.
  • Low-Demand Scenario: Assumes limited regulatory incentives and slow technological progress.
  • High-Demand Scenario: Assumes an ambitious energy transition, strong policy interventions (e.g., recovery mandates), and advanced recycling infrastructure.
• Quantification: Future material stock ($MS$) was calculated using the stock-flow-service nexus: $MS = Pop \times (S/Pop) \times (M/S)$, where $Pop$ is population, $S/Pop$ is per-capita infrastructure requirement, and $M/S$ is material intensity.
• Circularity Metrics: The study distinguishes between Maximum Supply Potential (theoretical outflow) and Actual Recovery Potential (accounting for systemic losses). Crucially, it calculates Closed-Loop Circularity (CLC), defined as the percentage of total material demand met by secondary materials reused at the same level of functionality, explicitly excluding downcycling.

Key Results
The analysis projects material flows from 2024 to 2070 under the three scenarios:

• Material Demand Trends:

  • Steel: Annual demand is projected to increase significantly by 94–104% by 2070 compared to 2024 levels, driven largely by the expansion of energy infrastructure (offshore/onshore wind, solar).
  • Concrete: Demand is projected to rise by 58–94%, driven by utility networks and renewable energy foundations.
  • Asphalt: Demand remains relatively stable, with a projected increase of only 1–2%, as the road network is mature and demand is driven by replacement rather than expansion.

• Supply and Recovery Potential:

  • Steel: Theoretical EoL supply could meet 74–86% of future demand. However, due to export dependence, contamination (e.g., hexavalent chromium), and regulatory barriers (NEN-EN 1090), realized closed-loop circularity is estimated at 31–40%.
  • Concrete: Theoretical supply could meet 71–83% of demand. However, widespread downcycling into low-value road foundations limits realized closed-loop circularity to 3–23%.
  • Asphalt: Theoretical supply could meet 92–101% of demand. Due to mature recycling frameworks and high Reclaimed Asphalt Pavement (RAP) usage, realized closed-loop circularity is estimated at 50–85%.

• Sectoral Shifts: By 2070, energy infrastructure is projected to account for the majority of steel (50–60%) and concrete (42–56%) stocks and outflows, shifting away from the historical dominance of highways and utilities.

Key Contributions

1. Comprehensive Scope: The study expands the scope of material flow analysis beyond buildings and mobility to include water, utility, and energy infrastructures, providing a holistic view of Dutch macro-infrastructure stocks.
2. Differentiation of Circularity: It explicitly quantifies the gap between theoretical recovery and closed-loop circularity, highlighting that high recycling rates (e.g., 98% for construction waste) often mask significant downcycling that fails to displace virgin materials.
3. Scenario Sensitivity: The analysis demonstrates how policy ambition and technological progress (specifically in the High scenario) can significantly improve circularity outcomes, with the High scenario achieving up to 13–35% higher circularity than the Reference scenario.
4. Identification of Bottlenecks: The study identifies specific systemic barriers, including the lack of domestic Electric Arc Furnace (EAF) capacity for structural steel, strict quality standards preventing high-value concrete reuse, and the logistical challenges of storing reclaimed asphalt in urbanized regions.

Significance and Claims
The authors claim that these findings provide a systems-level understanding of material circularity potential in the Dutch macro-infrastructure sector. The study asserts that while the theoretical potential exists to meet a large majority of future material demand with secondary resources, current systemic inefficiencies limit actual closed-loop circularity to a fraction of that potential.

The paper concludes that fully recovering EoL material stocks could reduce annual virgin material demand by 16–49% between 2024 and 2070. This reduction is presented as a critical component for achieving the Dutch government's 2050 net-zero emissions target. The authors emphasize that realizing this potential requires a synergistic approach integrating:

• Technological Innovation: Specifically, high-grade concrete upcycling and component-level reuse of structural steel.
• Policy Intervention: Stronger recovery mandates, secondary material incentives, and updated regulatory frameworks (e.g., moving beyond NEN-EN 1090 constraints).
• Design Interventions: Prioritizing design-for-disassembly, modularity, and material traceability.

The study positions the Netherlands as a representative case for other early-industrialized nations facing similar aging infrastructure challenges, offering transferable insights for transitioning toward infrastructural circularity.