Throughout the workshop, speakers made general observations about the issues associated with critical materials and the role of the chemical sciences in addressing those issues. These observations are gathered in this final chapter to capture the broad themes emerging from the workshop. These themes should not be seen as consensus conclusions of the workshop and are associated here with the speaker who made that observation.

• The level of criticality for a material depends on many factors, including physical availability, cost, importance in use, supply risk, concentration within a country, coproduction, potential for substitution, and environment and social concerns. (Eggert)
• The level of criticality for a material can change over time as the factors affecting criticality change. (Eggert)
• The importance of these factors differs from one material or element to another. (Eggert)
• Different groups have different definitions of critical materials depending on their needs and circumstances. (Eggert)
• Markets respond to both supply and demand signals but with time lags. (Eggert)
• Government has an essential role to play in pushing for undistorted international trade, streamlining regulation, facilitating the collection and dissemination of information, and facilitating research and development. (Eggert)
• The chemical sciences have an important influence on critical materials through research and development involving substitution, improvements in extraction and recovery, and improvements in manufacturing and recycling. (Eggert)
• Governmental policies also have a major influence on criticality, including policies on domestic production and processing, stockpiling, education, and diplomacy. (Bauer)
• Even if the price of a critical material is a small fraction of a catalyst, supply constraints can interfere with that application of the material. (Stevens)
• Research can reduce or eliminate the use of a critical material in a catalyst and thereby reduce or eliminate the effects of price or supply disruptions. (Chen)
• Replacing expensive metals with inexpensive metals in catalysts can produce significant savings and be more environmentally benign. (Bullock)
• Even in long-established applications like automotive catalytic converters, continued research can reduce the demand for precious metals, even where complete replacement of those metals is not yet feasible. (Lambert)
• Proven reserves of rare earths are growing rapidly, and one solution to tight supplies is to increase mining. (Shinar)
• Demand for some critical materials will soar if the world acquires a significant fraction of its energy from photovoltaics. (Zweibel)
• Resources constraints could be a critical factor in the development of grid-scale energy storage technologies. (Bradwell)
• Issues that need to be considered in establishing critical materials policies include trade restrictions, the extended times needed to develop new technologies, costs, and environmental impacts. (Whitacre)