Soutenance de thèse : Antoine Teixeira

Abstract

Global Greenhouse Gas (GHG) emissions related to the production of base materials are experiencing rapid growth, driven by global industrial and economic development. These emissions account for nearly one quarter of global emissions and pose major challenges in the fight against climate change. A particularly salient challenge is the incompatibility between existing National Low-Carbon Strategies (NLCS), which focus on reducing territorial emissions, and the globalized nature of material supply chains. In that context, there is a pressing need to identify more adequate sustainable national strategies that can balance overall material needs with carbon footprint reduction. This thesis explores various aspects of this question by developing integrated modeling experiments on the case of France.

The first part of this thesis examines the role of materials needs in shaping current and future carbon footprints under the framework of existing NLCS. Through a Multi-Regional Input-Output (MRIO) analysis, an introductory chapter provides an overview of the Carbon Footprint of Materials production (CFM) worldwide nowadays. It highlights the North-South disparity regarding the environmental impacts associated with the extraction and transformation of materials, where the South bears the burden of the impacts driven by the North’s final consumption. The absence of suitable tools to assess and map the CFM at a country scale for present situation and future scenarios motivated the development of the Hybrid Input-Output (HIO) MatMat model. Detailed in the second chapter, this tool supports the applications developed for the case of France in the rest of the thesis. The third chapter demonstrates that the CFM remains a blind spot in the NLCS of Western countries like France. In 2015 the CFM in France was approximately 3 tCO2eq per capita, and projections based on the official 2018 NLCS do not enable its reduction by 2050. Mapping the CFM along value chains and international trade reveals potential strategies to mitigate these emissions.

The second part of the thesis assesses the potential of two alternative strategies to balance material needs with the carbon footprint reduction in France: energy sufficiency and materials recycling. Based on the « Transition(s) 2050 » scenarios from ADEME, the fourth chapter shows that moving towards greater energy sufficiency allows to reduce more effectively France’s carbon and materials footprints in 2050, thus improving sustainability of consumption and production patterns. The fifth chapter explores materials recycling as a complementary strategy to enhance sustainability of NLCS. It demonstrates that deploying recycling to reduce imports rather than the production of primary materials is more effective in lowering carbon and material footprints. Concurrently, this strategy yields socio-economic co-benefits in terms of job creation and trade deficit reduction, while enhancing resilience against international price uncertainties. This chapter also proposes an innovative modeling framework: by linking the outcomes from the MatMat and the Computable General Equilibrium (CGE) Imaclim-S France models, it illustrates the added value of CGE models compared to traditional IO analyses to inform induced economic impacts.

This thesis underscores the need to improve and expand existing tools, currently limited to integrated energy-material analyses in the field of industrial ecology, to better represent key economic mechanisms that significantly influence prospective results. It calls for a rethinking of public policies and national low-carbon strategies to integrate the carbon footprint and broader environmental impacts. Notably, it proposes enhancing the integration of circular economy practices in transition scenarios, moving beyond recycling as a last-resort strategy in a robust sustainability framework.