Supply chain risk management for critical commodities: A system dynamics model for the case of the rare earth elements

We investigate mitigation strategies that potentially reduce the supply chain risk caused by exogenous interventions for critical commodities. We apply a system dynamics approach to examine the individual company's reaction in the rare earth elements (REEs) supply chain to China's introduction of export restrictions over a three-stage supply chain for 11 REEs, 10 semi-finished goods (SFG), and 21 finished goods (FG) between 2004 and 2015. We analyze how FG and SFG substitution, secondary recycling, supply extension and research and development (R&D) affect dynamic variables such as the price level, supply and demand on each stage to determine the effectiveness of each strategy for mining companies, SFG and FG producers. FG and SFG substitution show the highest potential for mitigating supply unavailability. Substitution is especially beneficial for FG producers. It also has the advantage of offering a quick development of alternatives for reducing REE supply unavailability risk. Due to the fact that the necessary infrastructure and technology are not available, secondary recycling shows only a low mitigation potential for FG companies. It was shown that mining companies do not invest proactively in supply capacities beyond China, as our simulation shows that it took 6 years until a new REE mine was opened. R&D is identified as a key element for REE mining companies, SFG and FG producers when it comes to developing alternative products and recycling techniques. Nonetheless, SFG producers face huge difficulties when trying to develop substitutes as alternative materials are not present.