This thesis explores the potential of increased recycling rates as a strategy to mitigate emissions, reduce waste accumulation, and alleviate material depletion across diverse regions and socioeconomic contexts. By developing and applying the JUSTICE-MATTER model, this research advances our understanding of how recycling, as a key component of a circular economy, can be integrated into broader climate policy frameworks to achieve sustainability goals.

The research methodology involved the development of a comprehensive matter use module based on the economy-wide material flow analysis (ew-MFA) framework that tracks material flows from extraction to disposal. This MATTER module provides a granular understanding of material usage across 57 regions, considering regional disparities in resources, economic activities, and socio-economic conditions. The JUSTICE-MATTER model integrates these material flows with climate and economic modules, offering a nuanced evaluation of how recycling policies impact emissions reductions, economic output, and material depletion under different Shared Socioeconomic Pathways (SSPs).

The findings highlight that recycling plays a significant role in reducing waste and conserving material resources, especially in regions with underdeveloped waste management systems. The transition to a Circular Economy (CE) in regions like Southeast Asia, Brazil, and parts of Africa resulted in substantial reductions in waste generation and material depletion. However, the impact of recycling on emissions reduction was found to be relatively modest, particularly in high-emission regions like China and Brazil. This suggests that while recycling is essential, it must be complemented by other strategies, such as transitioning to cleaner energy sources and implementing comprehensive emissions control policies, to achieve meaningful emissions reductions.

Economically, the effects of increased recycling rates varied significantly across regions. Regions with established recycling infrastructure, particularly in Europe, experienced minimal economic disruption from higher recycling rates. In contrast, regions like Chile and Brazil faced higher economic costs due to the need for substantial investment in upgrading recycling systems. These findings underscore the importance of tailoring recycling strategies to regional contexts, considering the economic and infrastructural disparities that influence the feasibility and impact of such initiatives.

The research highlights the importance of region-specific policies, emphasising differentiated approaches that address the unique challenges and opportunities of each region. While developed regions may focus on optimizing recycling processes, developing regions must prioritize infrastructure and capacity-building efforts. Despite the advancements in the JUSTICE-MATTER model, limitations such as static emission factors and a narrow focus on certain materials suggest areas for future refinement. Future research should incorporate dynamic emission factors, expand material analysis, and regionalise key parameters to reflect diverse economic and material use patterns more accurately.

In conclusion, this thesis contributes to advancing Integrated Assessment Models by integrating material flow dynamics into the JUSTICE-MATTER framework. Addressing the identified limitations and pursuing suggested future research directions will enhance the model’s capacity to guide global sustainability efforts and offer more robust policy recommendations for the complex challenges of the future.