Effective transition pathways toward circular economy based on integrated process models, economic models, and material flow analysis

循环经济倡议促进先进的材料回收和再循环技术、材料效率战略和非物质化解决方案。这些举措是旨在缓解气候变化、确保长期获得关键材料以及减少与填埋和资源开采有关的各种环境影响的政策的核心。然而，大规模采用这种循环战略的潜在好处和缺点大多仍未得到探索和量化。 即使一项特定技术的小规模使用提供了环境效益，也不一定意味着在整个经济中大规模采用这项技术就能保持这些效益。事实上，循环经济战略的适用性取决于多个因素：回收材料的污染程度；不同纯度的回收材料是否有足够的市场需求；达到回收材料纯度水平所需的能源、材料和资金要求；以及与这些要求相关的气候和环境影响等。所有这些因素都不能从目前的情况线性推断，需要广泛的情景开发才能有效地指导循环经济政策选择。 单独来看，来自物质流分析、生命周期评估和环境扩展投入产出分析的建模技术只能捕捉到这些因素的有限子集。因此，目前的研究方案基于这样一种假设，即需要对这些建模方法进行连贯的整合，以确定向更循环和更可持续的经济过渡的可信路径。因此，这项研究计划旨在通过开发一种新的分析框架来促进这种整合。 要建立这一框架，首要任务是将国家货币账户转换为整个经济中物质和能量流动的代表。第二项任务将开发用于废物回收、再循环、非物质化和轻量化的潜在技术的参数化预期模型。这项任务将努力考虑这些技术的材料质量要求，以及反过来，它们对物质流组成的影响。第三项任务将开发一种分析算法，将任务2的详细技术描述与任务1的更广泛的经济表述相结合。这一框架将用于确定大规模采用回收和非物质化战略的情景，重点是加拿大金属和塑料流动的循环性。这些案例研究将根据它们对气候缓解、资源保护和减少其他环境影响的总体好处进行评估，可能确定权衡的情况。

Circular economy initiatives promote advanced material recovery and recycling technologies, material efficiency strategies, and dematerialization solutions. These initiatives are central to policies aiming to mitigate climate change, ensure long-term access to critical materials, and reduce various environmental impacts linked to landfilling and resource extraction. Yet the potential benefits and shortcomings of a large-scale adoption of such circularity strategies remain mostly unexplored and unquantified. Even if the small-scale use of a given technology offers environmental benefits, it does not necessarily follow that these benefits are maintained for a massive adoption of this technology across the entire economy. In fact, the applicability of circular economy strategies depends on multiple factors: the level of contamination of recovered materials; the presence of a sufficient market demand for the recycled materials at different levels of purity; the energy, material, and financial requirements necessary to achieve these levels of purity in recycled materials; and the climate and environmental impacts associated with these requirements; among others. All these factors cannot be linearly extrapolated from the present situation, and extensive scenario development is required to effectively guide circular economy policy choices. Taken in isolation, modeling techniques from material flow analysis, life-cycle assessment, and environmentally-extended input-output analysis can each capture only a limited subset of these factors. The current research program is therefore based on the hypothesis that a coherent integration of these modeling methods is required to define credible transition pathways toward a more circular and sustainable economy. This research program therefore aims to contribute to such an integration through the development of a novel analysis framework. To build this framework, a first task will convert national monetary accounts into a representation of material and energy flows throughout the economy. A second task will develop parametrized prospective models of potential technologies for waste recovery, recycling, dematerialization, and lightweighting. This task will strive to account for the material quality requirements of these technologies, and conversely, their influence on the composition of material flows. A third task will develop an analytical algorithm to coherently integrate the detailed technology descriptions of task 2 in the broader representation of the economy from task 1. This framework will be used to define scenarios of large-scale adoption of recycling and dematerialization strategies, focusing on the circularity of flows of metals and plastics in Canada. These case studies will be evaluated in terms of their overall benefits for climate mitigation, resource conservation, and reduction of other environmental impacts, potentially identifying situations of trade-offs.