International Industrial Ecology Day 2021

Two responses to the unprecedented growth in demand for the mineral-based resources that will support the global transition to cleaner energy are material substitution and reuse of already extracted resources at higher rates. Reuse is of particular interest in regions that are heavily dependent on imports, especially of resources that face supply risks. Consistently maintained knowledge of regional material flows is needed to design and monitor closed-loop supply chains but established methods for tracking minor material flows of increasing significance rely heavily on empirical data that is limited in spatial resolution and resource intensive to procure, thereby limiting the regional specificity and reproducibility of many materials flow analyses and their application to supply chain planning. This study presents an economic input-output-based framework for elucidating the subnational trade structure of embodied critical materials, with a focus on cobalt as a case study. Globally, cobalt is primarily used in lithium-ion batteries, but its historical and current uses in the US are more diverse. Data on domestic cobalt use from the national Toxic Release Inventory (TRI) is used to highlight cobalt use by sector and region in a multiregional input-output (MRIO) model of the US. Network metrics are then applied to the MRIO model to test their suitability and identify competing uses for cobalt and potential secondary sources. The multiregional framework for mapping domestic supply chains has been demonstrated using a lithium-ion battery critical material but could potentially be applied to any material for which annual consumption data is available at the detailed sector level.