Quantifying the recoverable resources of by-product metals: The case of cobalt

Abstract The long-term availability of mineral resources is crucial in underpinning human society, technology and economic activity, and managing anthropogenic environmental impacts. This availability is increasingly true for metals that do not generally form the primary product of mines, such as copper or iron, but instead are recovered as by-products (or sometimes co-products) during the processing of primary ores—also known as ‘companion metals’ (e.g., indium, cobalt, molybdenum, rhenium, selenium). These metals, however, can be of significant economic and technological importance, both to a mine's economics and in downstream applications. It is therefore useful to develop methodologies to estimate the “recoverable resource” for such companion metals, i.e., the amount that could, if desired, be extracted and put into use over the next several decades. Monitoring the supply and demand of these resources is important to enable the identification of any changes that may have significant repercussions for the global economy, technology needs, and the environment. Here, we derive an estimate of the recoverable resource for cobalt (Co), a metal used with increasing frequency and in larger amounts in modern technology that is mainly recovered as a by-product of copper and nickel ore processing and production; Co-only mines are few in number and typically small in size. Our methodology combines the reported size of ore bodies that host Co with measured or estimated Co concentrations in the ores within these bodies. The dominantly by-product nature of Co means that uncertainties exist for some of the Co grades as well as recovery rates; given this, we also split our total recoverable Co resource, using a resource estimate data quality classification, into high, medium and low quality data, depending on factors such as whether statutory resource reporting codes were used during resource reporting. This methodology indicates that a minimum of 26.8 Mt Co is present in current global Co resources, with 15.2, 5.6 and 6.0 Mt Co in high, medium and low quality resources, respectively. Applying typical recovery rates for different ore types indicates that ~ 15.9 Mt of this Co is recoverable, with ~ 10.7, ~ 2.6 and ~ 2.6 Mt Co recoverable in high, medium and low quality resources, respectively. This approach provides a basis for determining similar recoverable resource estimates of other companion metals, such as indium, rhenium, selenium, etc., all of which are of increasing importance in modern day life.