Development of circular economy indicators starting from the in-use occupation of materials

Our society has an astounding and increasing consumption of materials. By 2050, three planets could be needed to provide resources for our current lifestyle. The world’s climate is the direct subject of how the global economy manages natural resources, and resource efficiency will be vital to meet the Paris Agreement’s temperature goals. In this sense, the circular economy concept can influence how we manage resources. The circular economy can promote the responsible and cyclical use of resources. In recent years, a circular economy has been endorsed as a policy to minimise burdens to the environment and stimulate the economy. The recent New Circular Economy Action Plan intends to achieve carbon neutrality and more efficiency in resources and materials management in the European Union. The supply chain of materials can much benefit from circular economy strategies to recover materials and products. However, despite the benefits of keeping materials in the loop, there will always be environmental burdens and cumulative use of resources associated with a chosen circular economy strategy. Thus, to target better policy towards a circular economy, indicators considering sustainability are needed. In the context of the Policy Research Centre for Circular Economy (Steunpunt Circulaire Economie) promoted by the Flemish Administration, this doctoral dissertation aimed to develop circularity indicators of materials in supply chains. As the initial step, this dissertation focused on understanding the state-of-the-art of circular economy indicators in chapter 2. A classification framework is proposed to categorise indicators according to the reasoning of what indicators measure (circular economy strategies) and how they do so (measurement scopes). There are plenty of circular economy strategies, but they can be grouped according to their attempt to preserve functions, products, components, materials, or embodied energy. The measurement scope can show how indicators account for technological cycles (with or without a life cycle thinking approach) or the effects of such cycles on environmental, social, or economic aspects. We illustrated the framework with micro-scale indicators from literature and macro-scale indicators from the European Union’s ‘circular economy monitoring framework’. The framework illustration showed that most of the indicators focus on preserving materials, with strategies such as recycling. Although micro-scale indicators can assess strategies considering a life cycle thinking approach, the European indicators often account for materials-based strategies without much life cycle thinking consideration. From the indicators considering life cycle thinking, few indicators assessed time, despite many circular economy definitions explicitly referring to an economy ‘where resources are kept for as long as possible.’ Furthermore, none of the analysed indicators could assess the preservation of functions (related to circular economy strategies such as sharing platforms). Finally, the framework illustration suggested that a set of indicators should be used to assess circular economy instead of a single indicator. Circular economy strategies of slowing and closing loops of resources have the ultimate goal of keeping materials useful (i.e., in-use) while avoiding losses (dissipation). With this reasoning, this dissertation proposed a set of indicators in chapter 3. We proposed measuring the circularity of materials by quantifying their in-use occupation, that is, the maintenance of materials in a useful state in products for as long as possible while avoiding dissipation or hibernation. Specifically, two indicators were developed: in-use occupation ratio (UOR) and final retention in society (FRS). These indicators were applied in two case studies (materials in laptops and wood products) with three scenarios each: linear, product preservation (reuse), and material preservation (recycling). The reuse scenarios generally presented a higher UOR (41–48% for laptop materials and 53% for wood) compared to recycling scenarios (29–45% for laptop materials and 52% for wood). Only two scenarios of wood products resulted in retaining materials for the next generation (FRS > 0%). We argue that the differentiation between supply, in-use, and hibernation phases is essential for a circular economy. UOR and FRS can measure the use of materials over time while considering life cycle thinking. In this sense, the in-use occupation-based indicators are a proxy for the benefit, or handprint, that materials provide in society. However, these indicators miss the connection with sustainability, particularly the environmental footprint caused by using such materials. Hence, in chapter 4, we further developed these indicators using the concept of resource efficiency to indicate the handprint and footprint of the used materials. We illustrated the developed indicators, resource efficiency of in-use occupation (EffOcc) and of final retention (EffFRS), with a case study of four materials (aluminium, copper, iron, and plastics) embedded in laptops. The study included scenarios with different circular economy strategies: energy recovery, recycling, refurbishing, and reuse. The scenarios showed the use of the materials in several cycles of laptops over a 25-year time horizon. Scenarios with cycles of refurbishment and reuse showed an improvement in EffOcc up to 189% and 157%, respectively, when compared to energy recovery. Nonetheless, it was remarkable that the average EffOcc and EffFRS showed a preference for refurbishing scenarios over reuse, considering the 25-year time horizon. Finally, we concluded this dissertation in chapter 5 with further analysis, perspectives, and concluding remarks. Firstly, we critically assessed the proposed indicators (chapter 3 and 4) against the classification framework (chapter 2). The proposed indicators can measure a wide range of circular economy strategies. However, more work is still needed to assess function-related strategies. Still, we suggested possible pathways so that indicators could analyse such strategies. Secondly, we suggested future development of the in-use occupation concept with life cycle assessment, particularly the development of impact assessment methods for material inaccessibility and suggestions for using the indicators in policy-making. Finally, we presented this dissertation concluding remarks