REMIND Materials: Coupling IAM and MFA to Model Synergies of Circular Economy and Decarbonization of Energy-Intensive Industries

Steel, cement, and chemical products, which serve as the foundation of economic development and daily life, account for 70% of annual greenhouse gas emissions of global basic material production and 16% of total anthropogenic emissions. Emission reduction is urgently needed to meet climate targets. However, these sectors are considered hard-to-abate: Mitigation options for primary production of material such as hydrogen- and bio-based processes, or carbon capture and storage (CCS) are indispensable, but face challenges such as high costs, often low technological maturity and sometimes limitations in their sustainable potential. This causes substantial uncertainty with respect to their short-term availability and long-term feasibility. Therefore, circular economy (CE) approaches - which reduce primary material demands through measures like material substitution, light-weighting, and recycling - are promising complementary alternatives partially due to their scalability, economic viability, and sometimes potential for early implementation. Moreover, they come with the co-benefit of mitigating other adverse effects of primary material production chains such as water use and pollution. Previous scenario modeling studies have explored material transition opportunities through two main approaches: technological substitution in production processes, and strategies from CE such as improvements in material efficiency and enhanced recycling and reuse. To fully capture these transformation options, as well as their interactions, the two research communities of scenario modeling and industrial ecology have increasingly collaborated in recent years. Here, we present REMIND Materials, an integrated approach that couples the integrated assessment model (IAM) REMIND with a dynamic material flow analysis (MFA) framework. REMIND links a macroeconomic general equilibrium model with a bottom-up engineering-based energy system model.  REMIND Materials adds process-based modeling of steel, cement, and chemical production. The MFA framework, represented by the in-house SIMSON model, captures demand, use, and recycling dynamics, enabling the representation of circular economy (CE) strategies such as recycling, reuse, and material efficiency improvements. This integration provides a comprehensive lifecycle perspective on energy-intensive industry pathways to carbon neutrality, including production process transformations, demand-side mitigation measures, and end-of-life strategies. This facilitates not only to investigate each single strategy’s impacts and potentials, but also to demonstrate the strong synergies and economic interactions between different mitigation options. The holistic approach provides decision-makers with critical insights to shape transition pathways that balance climate goals with economic feasibility.

Figure. REMIND Material Model Framework Overview