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@INPROCEEDINGS{Sltzer:1054085,
      author       = {Söltzer, Lana and Wortmann, Bernhard and Heinrichs, Heidi},
      title        = {{S}hen {M}aterials {M}atter: {E}ndogenous {R}esource
                      {C}onstraints in {G}lobal {E}nergy {S}ystem {O}ptimization},
      reportid     = {FZJ-2026-01719},
      year         = {2026},
      abstract     = {As clean technologies are adopted more widely as part of
                      the energy transition, more attention is being given to the
                      availability of critical materials that could constrain the
                      expansion of low-carbon infrastructure. Current ex-post
                      analyses of electrolyzers and batteries, based on planned
                      capacity expansions and market shares, indicate that the
                      demand for certain critical raw materials will exceed the
                      available supply, even when accounting for recycling and
                      battery reuse [1, 2]. Nevertheless, the majority of energy
                      scenarios still treat material availability as an external
                      factor or assume an unlimited supply in their underlying
                      energy system models. While recent advances have begun to
                      acknowledge material bottlenecks, many approaches rely on
                      external accounting layers as a post-processing step or use
                      abstract criticality indicators. Others lack an endogenous
                      representation of recycling and supply dynamics.
                      Consequently, material constraints rarely influence energy
                      scenarios. This study, therefore, addresses the
                      methodological gap in representing material availability,
                      circularity, and resource scarcity within long-term energy
                      system models. Here, we demonstrate that introducing
                      materials as explicit commodities, subject to balance
                      constraints, a dynamically emerging secondary supply, and
                      cumulative primary resource limits, fundamentally alters the
                      optimal pathways of the system compared to conventional,
                      unconstrained resource models. Using the
                      ETHOS.FINE.Resources extension, which we have developed for
                      the open-source ETHOS.FINE framework [3], we demonstrate
                      that technology deployment is directly influenced by
                      material feasibility, as well as by cost and operational
                      constraints. Unlike prevailing modelling practice, secondary
                      material supply arises endogenously from past infrastructure
                      stocks, thereby linking historical investment decisions to
                      future system feasibility. This reveals system-level effects
                      that remain invisible in post-processing approaches,
                      including shifts towards alternative technology portfolios,
                      altered deployment timing, and the increased strategic value
                      of recycling capacity. We apply the framework to a
                      regionalized global model spanning eleven world regions
                      characterized by their roles as major material importers and
                      exporters. The model encompasses key low-carbon
                      technologies, such as photovoltaics, onshore and offshore
                      wind, batteries (NMC and LFP), and electrolyzers (PEM and
                      AEL), as well as a wide range of critical materials (Li, Ni,
                      Co, Cu, Si, Pt, Ir, Dy, and Nd). Primary material supply is
                      modelled endogenously through the explicit representation of
                      existing mining operations and new mine investments,
                      including by-product modelling and geological reserve
                      constraints, as well as endogenous secondary supply from
                      recycling. This allows us to consistently quantify global
                      material requirements, identify potential bottlenecks, and
                      explore mitigation strategies such as ramping up recycling,
                      substitution, and supply diversification. By incorporating
                      material demand, recycling potential, and primary supply
                      into the model, the approach enables a systematic assessment
                      of circular economy strategies and resource efficiency
                      pathways, as well as their implications for energy system
                      design and environmental impact. The framework enables the
                      monitoring of progress towards physically feasible
                      transition pathways at national and global scales, revealing
                      trade-offs between cost-optimal and material-realizable
                      energy systems. By unifying energy system optimization and
                      resource dynamics, ETHOS.FINE.Resources supports more
                      physically credible transition assessments and provides a
                      quantitative basis for informing critical materials policy,
                      circular economy strategies, and resilient industrial
                      planning within urgent decarbonization timeframes. Beyond
                      our findings, we aim to engage in a critical discussion with
                      the ISIE-SEM conference audience regarding the most
                      promising avenues for further material-induced constraints,
                      as well as non-technical mitigation strategies and the
                      methodological options for incorporating them endogenously.
                      Finally, we will jointly seek feedback on the best
                      strategies to support the community with our tools and
                      data.},
      month         = {Jul},
      date          = {2026-07-06},
      organization  = {ISIE-SEM 2026, Cambridge (UK), 6 Jul
                       2026 - 8 Jul 2026},
      cin          = {ICE-2},
      cid          = {I:(DE-Juel1)ICE-2-20101013},
      pnm          = {1111 - Effective System Transformation Pathways (POF4-111)
                      / 1112 - Societally Feasible Transformation Pathways
                      (POF4-111)},
      pid          = {G:(DE-HGF)POF4-1111 / G:(DE-HGF)POF4-1112},
      typ          = {PUB:(DE-HGF)1},
      url          = {https://juser.fz-juelich.de/record/1054085},
}