The concept of Circular Economy is a principle aiming to improve sustainable development by reducing resource use and impact on ecological systems. An increasing number of companies are applying this theory on design strategies and business models in order to close, slow and narrow material loops. To highlight the importance, guide practitioners, and evaluate the progress of circular economy, a high number of circularity metrics (C-metrics) have been developed. However, little attention has been given to creating a connection between quantification of circularity and environmental performance. Existing metrics also do not highlight the interplay between micro (product), meso (industrial symbiosis), and macro (regional) level circularity. Moreover, existing metrics do not capture all material loops and do not adopt a value chain perspective on material flows. To improve the connection between C-metrics and environmental performance, a framework connecting circular economy strategies and material flows was developed. Based on this framework, a material flow-based C-metric was designed aimed at converting mechanisms of closing, narrowing and slowing material loops into a single-point value. To evaluate its feasibility, the metric was tested on three circular business models that represent all three mechanisms in a value chain perspective. The results showed that the metric is feasible in more situations than existing metrics and that the circularity value is highly dependent on assumptions. In future studies, the metric should be tested and compared to Life Cycle Assessments on multiple system levels to ensure that it generates valid results. Furthermore, user input assumptions should be standardized to ensure metric reliability.

The concept of circular economy consists of a wide range of strategies that aim to reduce the environmental impact of production systems and consumption patterns through increased circularity of resources. Circularity is mostly associated with material efficiency strategies that either close, slow or narrow loops, and a multitude of circularity metrics have been developed to evaluate the efficiency of such strategies. Relatively little effort has been made to quantitatively assess the connection between circularity, material efficiency, and environmental sustainability. More knowledge is required about how material-based circularity metrics can be used to guide practitioners of the circular economy towards strategies that foster environmental sustainability. In this study, a novel structured approach is adopted to perform such a comparison by including closing, slowing, and narrowing strategies on a lawn mowing case. Four circularity metrics that can capture material strategies throughout product value chains (Material Efficiency Metric, Material Circularity Indicator, Circularity Potential Indicator and Circular Economy Indicator Prototype) are compared to three complementary midpoint categories using Life Cycle Assessment (Global Warming Potential, Material Resource Scarcity, and Human Non-Carcinogenic Toxicity). The results show that the studied circularity metrics generate accurate results when evaluating Material Resource Scarcity and that they rank the material efficiency strategies equally with all environmental impact categories. The circularity metrics are unable to capture the benefits of reduced energy and the correspondence to all impact categories is lower in scenarios with higher energy use. We conclude that the strength of the studied circularity metrics is twofold: i) promoting solutions that reduce material demand and waste creation and ii) highlighting the advantages of combining complementary circularity strategies. This research shows that the material-based circularity metrics can be valuable guidance tools for practitioners of circular economy, as they do not require methodological expertise and can align the results with Life Cycle Assessments in some specific situations. More comparisons between circularity metric results and Life Cycle Assessments are needed in future research to establish state-of-the-art circularity metrics for specific situations and purposes, including energy-focused circularity metrics.

To assess the progress towards a circular economy, numerous circularity metrics have been developed in recent years. However, there is a lack of alignment between circularity metric results and greenhouse gas emissions, as circularity metrics are mainly geared towards capturing material efficiency of circularity strategies and mostly disregard energy use. We target this gap by developing a new mass-based circularity metric that considers both material and energy resources (i.e., fuel and electricity). The circularity metric results are compared to the midpoint impact category Global Warming Potential in two case studies, where circularity strategies are applied to energy consuming products in several different scenarios. The results show that by including energy resources, the new metric is more aligned with GWP than purely material-based metrics. We discuss how this alignment changes in different systems and in which situations the circularity metric is a suitable proxy for GWP. 

Firm-level adoption of circular business models is a crucial part of the transition toward circular economy, but companies that delve into such pursuits often encounter a series of barriers that hamper their success. Although multiple studies on barriers to circular economy have been made, there is a lack of understanding of how barriers are formed under firm-specific characteristics such as sectoral conditions and the type of circular business model adopted. To bridge this gap, we illustrate a barrier framework in a multiple-case study including nine Swedish firms. We derived about 28 barriers within five categories of circularity approaches (design, waste, service, platform, and nature) across three sectors (furniture, electronics, and garment). This research contributes to the circular economy literature by revealing how adhering to certain sectors and circular business approaches significantly changes the way barriers are perceived by firms. The outcomes may support both practitioners and policymakers as they facilitate circular economy transitions.

Parallel to increasing attention given to solutions within the circular economy (CE) paradigm, the academic body of literature applying lifecycle assessments (LCAs) of circular economy initiatives is growing. However, as the portfolio of circularity strategies is rich and there are numerous products on which LCAs can be applied, there are still gaps in this body of literature. There is thus a demand for systemizing existing LCA studies, specifically to uncover the reduction potential of greenhouse gas (GHG) emissions in specific systems. To this end, a scoping literature review was conducted, aiming to uncover knowledge gaps concerning the potential of reducing GHG emissions with CE strategies. The study targeted LCA studies assessing circularity from product lifecycle perspectives and organized them according to the specific products and types of CE strategies assessed within them. Gaps were identified by comparing the consumption-based GHG emissions of five distinct consumption categories to the number of studies found within them.

The results revealed that LCA studies are mainly linked to one of the following four focus areas: prolonging lifetime of buildings and their components, free-floating vehicle systems, garment rental strategies, and prolonging lifetime of appliances. Food and mobility are underexplored consumption areas in relation to their related GHG emissions and preferred strategies according to the 9R framework appear less than those of lower priority. The findings indicate that the lack of LCAs within specific settings is either related to a lack of study objects or to a disconnect between these strategies and the understanding of CE in relation to these categories. This paper provides a synthesis of these findings and suggestions for future research, aiming at guiding future studies to fill the discovered gaps.