Secondary sources can form an important part of the future cobalt supply as large quantities of cobalt end up in waste streams at different stages in the value chain. As cobalt is mainly a by-product to copper and nickel, metallurgical processing routes are not optimised for cobalt recovery and a significant proportion ends up in mining wastes. In addition, manufacturing waste (new scrap) can be recirculated to ensure more efficient use of cobalt components. However, the largest secondary future cobalt resource are most likely end-of-life (EOL) products, particularly lithium-ion batteries (LIB) in electric vehicles (EV), which will gradually become more available for recycling.
In many mining operations, cobalt is not be prioritised for recovery as it only makes up a small proportion of the revenue compared to the main commodities of copper, nickel. It is estimated that between 40-60% of cobalt is lost during ore processing to make a concentrate. Equally, smelting of sulfide ores from magmatic Ni-Cu-Co sulfide deposits only recover roughly 60% of cobalt, but 80% of nickel. The remainder will end up in the waste streams in mine tailings or as slags from smelting. There are several projects in Central Africa that attempted to recover cobalt from tailings (Petavratzi et al. 2019). A successful example is the Kasese project in Uganda , which recovered cobalt from pyrite-rich mine tailings via a bioleaching process on an industrial scale. The facility produced 800 tonnes of cobalt per year from 1998–2014 (BRGM, 2023).
Another study at Nkana (Zambia) investigated the reprocessing of slags to produce a cobalt-rich alloy that can be further refined into cobalt metal. The Nkana site contains 20 million tonnes of slag with an average cobalt content of 0.76%, higher than cobalt grades in many cobalt-producing mines. However, the process was never fully implemented and the operator decided to use a less expensive technology with no cobalt recovery (Petavratzi et al. 2019).
The International energy agency (IEA) forecasts that the amount of spent lithium-ion batteries will surge after 2030 with 1 TWh reaching their EOL by 2040 (SDS scenario) (IEA 2021). An EV battery contains between 5-33% cobalt among many other valuable materials. Successful recycling depends on the collection of EOL products, battery type and cobalt price. Battery recycling involves mechanical recovery, pyrometallurgy and hydrometallurgy or a combination of the three. Recycling efficiency of cobalt from lithium-ion batteries are with more than 85% relatively high (Tkaczyk et al. 2018).
Other important waste streams include scrap from superalloys and nickel-cobalt alloys as well as catalysts. These are often recycled in existing or secondary smelting facilities (i.e. pyrometallurgy). Spent cemented carbide (cobalt-bearing hard wearing tools) can be recycled via the zinc method and produce cobalt metal powder (Petavratzi et al. 2019).
UNEP estimates an overall EOL-recycling rate of 68% cobalt, but the recycled content in newly fabricated cobalt metal is only 32% (UNEP 2011).
The main challenges to increase cobalt recycling are (Petavratzi et al. 2019:
1. Economics of the scrap material, i.e. presence of other valuable materials and uncertainty material composition, making large-scale and efficient recycling difficult.
2. Poor EOL collection rates, which effects the viability of the recycling sector.
3. Hibernating stocks of e.g. consumer electronics. and lack of consumer engagement associated with waste management.
BRGM, 2023. 1995 - BRGM and the KCC project. Bureau de Recherches Géologiques et Minières (BRGM), Orleans. Accessed: 19/01/2023. Available at: https://histoire.brgm.fr/en/instants/1995-brgm-and-kcc-project.
IEA, 2021. The role of critical minerals in clean energy transitions - World energy outlook special report. International Energy Agency, Online. 287 p. Available at: https://iea.blob.core.windows.net/assets/24d5dfbb-a77a-4647-abcc-667867207f74/TheRoleofCriticalMineralsinCleanEnergyTransitions.pdf.
Petavratzi E, Gunn AG, Kresse C, 2019. Cobalt. BGS Commodity Review. British Geological Survey. 72 p. Accessed: 220/10/2023. Available at: https://www2.bgs.ac.uk/mineralsuk/download/mineralProfiles/BGS_Commodity_Review_Cobalt.pdf.
Tkaczyk AH, Bartl A, Amato A, Lapkovskis V, Petranikova M, 2018. Sustainability evaluation of essential critical raw materials: cobalt, niobium, tungsten and rare earth elements. Journal of Physics D: Applied Physics. 51:203001. https://doi.org/10.1088/1361-6463/aaba99.