Circular Economy Beyond Circularity: Where Should the Boundary Lie?

Circular economy (CE) is increasingly discussed not only as a strategy for slowing, closing, and narrowing material loops, but also as a broader route to sustainability. This expansion has made CE more influential, but also less clearly bounded. Drawing on three related studies, we argue that CE has moved well beyond its traditional circularity core yet still does not match sustainability in a balanced or complete way. Broad SDG alignment is therefore not enough to treat CE as equivalent to sustainability. The challenge is not to stop CE from expanding, but to govern that expansion. We propose two responses. First, stronger large-scale mapping systems are needed to assess CE’s sustainability reach with greater precision and consistency. Second, CE should be structured through a two-tier model with explicit boundary rules: CE-Core captures circularity-specific value retention, while CE-Plus includes only those wider domains that enable, govern, or evaluate circular interventions.