Benjamin Sprecher
Yale University, School of Forestry and Environmental Studies, Center for Industrial Ecology
Benjamin Sprecher is an assistant professor at the Leiden University Institute of Environmental Sciences, where he works on urban resilience and resilience in the supply chains of critical materials.
As new technology is introduced, demand for certain materials will increase and demand for others will diminish. Base metal supply is generally elastic and can be expected to respond to demand. Most minor metals (‘companion metals’) are co-produced with base metals, according to geologically dictated relationships. These companion metals often have severely limited supply elasticity, because their relatively small revenue subordinate them to economic drivers of the primary base metal. If technological or societal change leads to a major demand reduction for a base metal, this could cause significant supply constraints of its companion metals.
In this work, we explore this dynamic by constructing two scenarios for disruptive ‘black swan events’, an unexpected event with major consequences. We model the large-scale adoption of graphene for both electricity transport and corrosion protection. The resulting reduction in demand for copper and zinc potentially constrains the production of several by-products of these metals, specifically germanium, indium, molybdenum, silver and cadmium. Our scenarios assume that over the period 2025-2040, 25% and 33% of copper and zinc demand will be substituted, respectively. We find that the companion metals fall in three categories:
1) the nuisance companion: cadmium (which occurs in 100% of zinc bearing ores) can be considered a nuisance element. Our results indicate that as of 2014 half of the available cadmium was dumped in some form before being refined into metal. Without any disruption, we find that this excess of cadmium will further increase while a disruption will lead to a somewhat reduced cadmium oversupply.
2) the low volume companion: germanium and indium show a modest supply deficit without a disruption, which increases to a deficit of 20-50% in 2050 if confronted with a black swan event. Both elements face challenges in scaling up production significantly beyond current zinc co-production levels. Germanium is recovered in the gas cleaning stream of zinc smelters. Often the concentrations are not high enough to justify extraction. In the case of indium, only fully integrated zinc processing chains with suitable feeds will have the overall volume and technology necessary to achieve the internal recycling streams that are necessary to achieve economically recoverable indium concentrations. Physically, enough alternative sources of these hard to produce metals exist, but price would need to go up very significantly to exploit these.
3) the profitable companion: silver and molybdenum. the overall market of these metals will be only moderately impacted by a black swan event (10-20% deficit). The primary production of both of these metals is more diversified and thus less susceptible to single point failure. A qualitative analysis of the Mo and Ag supply chains leads us to conclude that both metals are not significantly restricted in their supply elasticity. For Mo, there are several primary Mo mines that, while having a higher cost-base than Cu-Mo mines, could swing into production if necessary. In the case of silver, the co-production fraction is often high enough that several mines could switch from being primarily zinc driven mines to becoming lead-silver mines.
• Complexity, resilience and sustainability , • Socio-economic metabolism and material flow analysis
