The Production of Critical Materials as By Products

This issue of material criticality has been receiving much attention recently from governments all over the world. The United States and the European Union have two different definitions of what makes a material critical. The United States Department of Energy (DOE) defines criticality in two ways: (A) supply based risk based on projected market balances, competing energy demands, political, regulatory and social factors, co-production risks, and producer diversity; and, (B) importance to clean energy based on clean energy demand and substitutability 1. Net import reliance can hint at the supply based risk for materials. Figure 1 shows the United States net import reliance for materials of interest.