The global supply of cobalt was simulated by combining 3 different system dynamics models; BRONZE, PGM and STEEL. The present use of cobalt shows a low degree of recycling and systemic losses are significant. The reserves of cobalt are not very large (20-25 million ton extractable) as compared to metals like copper, zinc or iron, and after 2170 cobalt will have run out under a business-as-usual scenario. The present business-as-usual for cobalt use in society is therefore not sustainable.