What do product-level circular economy indicators measure?

Recently, the concept of circular economy (CE) has become more popular amongst researchers and practitioners as a solution to current unsustainable production and consumption practices. Several indicators meant to quantitatively assess the CE have been suggested in both the academic and grey literature. For companies, indicators are crucial for monitoring progress and to support decision making towards improved circularity. However, no consensus regarding the definition of the CE exists and as a result there is a significant divergence of what CE indicators in fact measure. Taking a product-system perspective and focusing on resources, we review existing CE indicators at the product-level and map the physical resource flows they quantify over the life cycle on a novel, generic system model in the form of a flowchart. The analysis highlights the difference between the indicators and shows that most only address parts of the life cycle with a focus on recycling-related flows. Existing gaps identified primarily relate to the use phase, e.g. lifetime extension measures like repair, maintenance, or repurposing, but also include other relevant aspects in the use phase like energy auxiliaries. The constructed flowcharts can guide the future development of indicators or point to ways of combining several indicators to capture larger parts of the product system.