Designing sustainability under Earth-system rate constraints

Abstract

Sustainability debates are monopolized by quantities: total energy use, material stocks, or recycling volumes. These metrics are informative, but they obscure a more fundamental constraint. On a materially closed but energetically open Earth, long-term viability is governed by rates: power density, areal power density, and the rate at which dispersed materials can be repurified under dif- fuse solar fluxes. We develop a physical framework that links technological metabolism, material dilution, and recycling limits through these rate con- straints. This perspective clarifies why many contemporary technologies remain viable only through stock drawdown and high-power buffering, and why green growth strategies often shift rather than resolve the underlying mismatch between industrial activity and Earth-system dynamics. We argue that long-term sustain- ability requires both quantitative reduction in aggregate industrial throughput toward rate-bounded regimes and the development of technologies qualitatively compatible with biospheric operating conditions.