Global Technogeochemical Flows of Iron from Lithosphere to Technosphere

Anthropogenic material fluxes have reached magnitudes comparable to natural biological and geological processes, yet they are rarely addressed within integrated Earth system frameworks. Iron, the most abundantly extracted metal from Earth’s lithosphere, is primarily used for steel production and constitutes a fundamental material basis of modern infrastructure and societal development worldwide. However, data on iron extraction, production, and use remain fragmented across national inventories and are rarely spatially linked to end-use sectors, limiting our ability to assess its role in the Anthropocene Earth system.

Here, we present a new approach based on global technogeochemical flows and apply it to the approximately 2 Gt yr⁻¹ anthropogenic flows of iron. We synthesize disparate datasets using the SESAME gridding tools to demonstrate how iron extracted from a limited number of locations, about 2.3% of global land grid cells, is transformed through a similarly concentrated set of steel production sites, about 2.7% of land grid cells, before accumulating in widely distributed in-use stocks. Using a spatiotemporal, grid-based material flow analysis combined with a tariff-weighted gravity model, we link iron extraction and steel production to end-use sectors at the full planetary scale.

Our results show that Eastern Asia functions as the dominant global locus of iron flows from extraction to in-use, accounting for over 50% of global crude steel production and nearly 44% of total in-use stock accumulation between 2000 and 2016. At the global scale, the network flow models indicate that approximately 2/3 of total mass displacement occur between iron source locations and steel production sites, about 10.4 Tt·km, while 1/3 occurs between steel production and in-use locations, about 5.2 Tt·km. This combined displacement exceeds the total mobility of all human beings by a factor of four.

By explicitly resolving the spatial and temporal interconnections of iron flows, this work advances a systems-based understanding of how industrial economic processes are physically embedded within the Earth system. The approach highlights the uneven spatial distribution of societal pressures and material dependencies that underpin sustainability challenges in the Anthropocene. More broadly, this spatiotemporal framework can be extended to other critical minerals, offering a pathway toward integrative and transformative research on Earth and societies.