Comparison between circularity metrics and LCA: A case study on circular economy strategies

Abstract

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.