Integrated assessment models (IAMs) have become crucial tools for analyzing strategies to mitigate climate change, but many still lack the granularity to fully depict material flows and stocks. The new MESSAGEix-Materials module aims to bridge this gap by incorporating detailed representations of material extraction, production, processing, and end-of-life management within the MESSAGEix modeling framework.
This open-source model provides a systems-level perspective on the material-energy-emissions nexus, enabling more holistic assessment of the decarbonization potential across energy-intensive industries. The latest version, MESSAGEix-Materials 1.1.0, focuses on four major sectors: aluminum, iron and steel, cement, and petrochemicals. By interlinking material stocks and flows with energy demand and greenhouse gas emissions, the model offers novel insights into the complex trade-offs and synergies involved in realizing a sustainable, net-zero future.
Material Flow Representation
Conventional energy system models have traditionally focused on tracking energy commodities, from primary resource extraction to final energy use. However, this approach often overlooks the vital role of materials in driving energy demand and emissions. MESSAGEix-Materials addresses this shortcoming by adopting the principles of material flow analysis (MFA) – a methodology rooted in industrial ecology that comprehensively accounts for the physical stocks and flows of materials throughout the economy.
The model’s systems-level definition encompasses the entire material lifecycle, from raw material extraction, through industrial processing and manufacturing, to the accumulation of material stocks in end-use applications and eventual waste management. This holistic framing enables the integration of circular economy strategies, such as recycling and material efficiency, directly into the optimization framework.
Systems Optimization Model
MESSAGEix-Materials is implemented within the broader MESSAGEix modeling ecosystem – a family of global and country-level IAMs built upon the open-source MESSAGE linear programming model. The integration of material flows and stocks into this systems optimization framework represents a significant methodological advancement, allowing for the study of complex interactions between the energy system, industrial processes, and material demands.
The model’s cost-minimizing objective function now considers not only the traditional energy system parameters, but also the techno-economic characteristics of material production technologies and the dynamics of material stocks. This empowers the model to identify least-cost pathways for decarbonizing energy-intensive industries, accounting for material-oriented mitigation strategies in addition to conventional energy efficiency and fuel switching measures.
Material Flows in Systems Modeling
The explicit representation of material flows and stocks within an integrated assessment modeling context opens up new avenues for analysis. For the power sector, for example, the model can now endogenously determine the material requirements (e.g., steel, cement, aluminum) for building new electricity generation capacities, as well as track the retirement and recycling of these materials over time.
This enhanced material accounting enables a more nuanced understanding of the implications of the energy transition. Increased electrification and the scaling up of renewable energy technologies, while crucial for decarbonization, can also drive significant additional demand for energy-intensive materials. By quantifying these material-related impacts, MESSAGEix-Materials provides a more comprehensive assessment of the overall costs and emission reduction potential of different mitigation pathways.
MESSAGEix-Materials Framework
Version 1.1.0 Release
The latest version of MESSAGEix-Materials, released as v1.1.0, focuses on the four most energy- and emission-intensive industrial sectors: aluminum, iron and steel, cement, and petrochemicals. These industries account for a substantial share of global energy use and direct CO2 emissions, making their decarbonization crucial for achieving climate goals.
The model represents the full material lifecycle for these sectors, from raw material extraction to product manufacturing, stock accumulation, and end-of-life waste management. This encompasses processes such as bauxite refining, steel production via blast furnaces and electric arc furnaces, cement clinker production, and the steam cracking of hydrocarbon feedstocks to produce high-value chemicals.
Model Enhancements
A key enhancement in this version is the endogenization of material flows linked to the installation and retirement of energy infrastructure, particularly for the power sector. This allows the model to capture the material requirements and associated emissions resulting from the buildup of low-carbon electricity generation capacities, such as wind turbines, solar photovoltaics, and nuclear plants.
Additionally, the representation of recycling processes and material trade has been expanded, enabling a more comprehensive assessment of circular economy strategies and their implications for energy use and emissions. The model also incorporates novel carbon capture and storage (CCS) pathways tailored to the specific production processes of each industry.
Applications and Use Cases
The enhanced capabilities of MESSAGEix-Materials open up new avenues for research and policymaking. By integrating material flows with energy systems modeling, the framework can now provide deeper insights into the synergies and trade-offs between material efficiency, circular economy, and conventional energy-focused mitigation strategies.
For example, the model can be used to investigate the material implications of achieving ambitious climate targets, such as the EU’s goal of reaching net-zero emissions by 2050. It can also shed light on the material supply chain challenges and investment needs associated with the widespread deployment of low-carbon technologies required for the energy transition.
Moreover, the model’s detailed representation of industrial processes enables the assessment of sector-specific decarbonization pathways, including the role of technologies like hydrogen-based steel production, CCS in cement kilns, and biomass-derived chemicals. This granularity is crucial for designing effective, tailored policy interventions to support the transformation of energy-intensive industries.
Material Flows in Energy Systems
Energy System Dynamics
The integration of material flows within the MESSAGEix modeling framework allows for a more robust representation of the complex dynamics between energy systems and material demands. As the energy transition progresses, the increased deployment of renewable energy technologies and electrification across end-use sectors can drive significant changes in the material requirements for the energy system itself.
For instance, the model can now endogenously determine the material stocks needed for electricity generation infrastructure, such as the steel, cement, and aluminum used in wind turbines, solar panels, and power transmission networks. By accounting for these material-related impacts, MESSAGEix-Materials provides a more comprehensive understanding of the overall system costs and emission reduction potential of different decarbonization pathways.
Material Demand and Supply
The detailed representation of material production processes within the model also allows for a better characterization of industrial material demands and their evolution over time. This includes capturing the shifting patterns of material use, as well as the potential for increased material efficiency and recycling to offset primary material production.
Moreover, the model’s treatment of material trade enables the assessment of global supply chain dynamics and the implications for regional resource availability and energy use. This is particularly relevant for addressing concerns around critical material supplies, such as the availability of key metals required for low-carbon technologies.
Circular Economy Considerations
By explicitly modeling material stocks and flows, MESSAGEix-Materials provides a platform for evaluating the potential of circular economy strategies to contribute to climate change mitigation. The representation of recycling processes, waste management, and the dynamics of material stocks in end-use applications allows the model to assess the energy and emissions impacts of measures such as material lifetime extension, reuse, and closed-loop recycling.
This systems-level perspective is crucial for identifying synergies and potential trade-offs between circular economy initiatives and other decarbonization approaches. For instance, the model can help quantify the emission reduction benefits of increased steel recycling, as well as the additional energy demands and material requirements this may entail.
Optimization Techniques
At the heart of MESSAGEix-Materials is a linear programming (LP) optimization model that seeks to minimize the overall system costs while adhering to various constraints, such as emissions targets, resource availability, and technology deployment rates. This cost-optimal approach enables the identification of the most economically efficient decarbonization pathways for energy-intensive industries.
The model also incorporates mixed-integer programming (MIP) elements to handle discrete technology choices, such as the selection between different production processes or the deployment of carbon capture and storage facilities. Additionally, ongoing research is exploring the potential of nonlinear optimization techniques to better capture the inherent complexities of material flows and industrial processes.
Through these advanced optimization methods, MESSAGEix-Materials aims to provide policymakers, industry stakeholders, and researchers with a robust and flexible modeling platform to navigate the intricate challenges of decarbonizing the material-intensive sectors of the economy. By bridging the worlds of energy systems and industrial ecology, this open-source model promises to deliver crucial insights for achieving a sustainable, net-zero future.
