Materials in energy system modelling: A review and integrated energy–material framework for circular economy and decarbonisation pathways

Achieving climate neutrality requires transforming both energy and material systems. Energy system models (ESMs) are central to assessing decarbonisation pathways, yet they lack a consistent representation of material dynamics, limiting their ability to capture material-related energy demand and the role of circular economy (CE) strategies in reducing it. Material flow analysis (MFA), on the other hand, provides a detailed representation of material stocks, flows, and circularity, enabling the assessment of material system evolution, but does not explicitly capture the associated energy demand, emissions, and broader energy system implications. This study presents a review of how industrial sectors, material flows, supply chains, and CE strategies are represented in ESMs. Based on this assessment, three state-of-the-art models, FORECAST, IESA-Opt, and IMAGE-TIMER, are reviewed in greater detail. The review reveals that, despite recent improvements in industrial representation and the inclusion of CE strategies, inter-sector material supply chains are rarely modelled, leading to inconsistencies in associated energy demand representation, while CE elements remain largely fragmented and exogenous. Building on these findings, we introduce dynamic MFA (dMFA) as a complementary approach for representing materials and develop a conceptual integrated ESM-MFA framework. The framework identifies explicit interlinkage points, clarifies their functional roles, and maps CE strategies to appropriate modelling components. It aligns material demand with production and enables a consistent estimation of material-related energy use and emissions within energy system modelling, while also highlighting key methodological challenges associated with integration. Overall, the framework strengthens the assessment of the energy transition and supports integrated energy-material scenario development, enabling circularity-informed decarbonisation pathways.