Physical work generation requires the existence of a heat gradient, according to the universal notion of the Carnot Heat Engine; also the corner stone of the exergy concept. Heat gradient availabilities fundamentally drive systems’ evolution. However, exergy is consumed irreversibly, via its gradual transformation to entropy. Extending Roegen's postulations, it is argued that exergy consumption founds economic scarcity, via: (a) human difficulty to produce large heat gradients on the Earth and (b) irreversible depletion of existing ones. Additionally, in the emerging Anthropocene epoch, exergy upgrades to a core concept for interpreting thermodynamically natural resource degradation and energy paradigm transitions.
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