Digital twins and cyber-physical systems for sustainable manufacturing: Enabler or illusion?

Digital twins and cyber-physical systems are routinely presented as engines of sustainable manufacturing, promising large reductions in energy use, materials, and emissions. This commentary asks whether this promise is an established fact or a conditional hypothesis. Reviewing the conceptual foundations—from the origin of the digital twin idea and the five-level cyber-physical-systems architecture to the crucial but widely blurred distinction between a digital model, a digital shadow, and a true digital twin—I show that much of what the industry labels a digital twin lacks the bidirectional coupling that the concept requires. I then survey the sustainability case, which is genuine but rests largely on simulations and review-level syntheses, and foreground a counterargument that the field too often ignores: the energy and carbon cost of the computing infrastructure on which twins run, and the rebound effects that can erode or reverse efficiency gains. I argue that the net sustainability benefit of digital twins is not automatic but conditional, that it must be demonstrated with a system-boundary life-cycle assessment that internalizes the twin’s own footprint, and that interoperability, security, and equitable access for small firms are the practical constraints on scaling. I conclude with a research agenda and a reading of the Industry 5.0 turn as a normative reframing that still awaits empirical proof.