The greater than 109 km3 volume of the deep-sea water column and greater than 300 × 106 km2 area of the deep-sea floor represent a major natural capital asset. Global society has been utilising space in the deep ocean as a reservoir for solid, liquid, and hazardous waste produced by terrestrial-based societies, as a buffer that absorbs nonsolid, nonliquid industrial waste streams, specifically CO2 from fossil fuel and biomass burning, heat from a warming atmosphere, and as freely available and convenient space. High-value uses such as the deployment of transoceanic telecommunications cables provide substantial, near-term economic and societal returns with minimal environmental impact. Low-value uses of this natural capital as empty space to absorb waste have arguably enabled industrialisation to continue further along an unsustainable trajectory than would have occurred had there been no such waste buffer available.