REDUCING DEPENDENCE ON CRITICAL

METALS AND MINERALS

OVERVIEW

The precious metals (Ru, Rh, Pd, Os, Ir, Pt) make highly effective catalysts in a wide range of chemical reactions, due to their readiness to change oxidation states and their reluctance to form recalcitrant oxides. Unfortunately, they are also some of the least abundant elements in the Earth’s crust. Over the course of the past century, many metals have been extracted from virgin ores at exponentially-increasing rates, to meet the infrastructure and industrial needs of rapidly industrializing societies in North America and Europe. Widespread implementation of new technologies, such as fuel cells, maybe strongly limited by the availability of these metals. For example, the in-use stock of platinum (Pt) needed for a fleet of 0.5 billion H2 fuel-cell cars (i.e., approx. half of the world’s current passenger vehicle fleet) would exhaust our remaining lithospheric stock of Pt in just 15 years, even if there were no competing uses for Pt.

 

Many other emerging technologies rely on uncommon elements. They may be relatively abundant but very highly distributed (e.g., the not-so-rare “rare earths” used in permanent magnets for electric vehicles and wind turbines). This results in high environmental costs for their extraction and purification. Alternately, their supply may be strongly limited by co-production, due to their occurrence as minor impurities in other metal-containing ores (e.g., In, Ga and Te used in photovoltaics and solid-state lighting). Rapid demand growth and geopolitical supply-security risks also pose impediments to large-scale deployment. Consequently, many are now widely considered to be critical elements, for which supply limitations and/or disruptions pose significant threats to our economic and/or social well-being. It is becoming urgent to minimize their use, replacing them wherever possible with Earth-abundant metals in large-scale applications. Sustainable design of processes and/or materials involving critical elements must take into account supply security, long-term availability and the environmental impact of production. How a material will be used, disposed, reused, or recycled is also key: the fate of a material through its use and end-of-life phases is largely determined during the design phase. Dissipative uses of critical elements can make material recovery prohibitively costly, and must be avoided.

CHEMICAL INDUSTRY SUSTAINABILITY

The US chemical industry is a cornerstone of American manufacturing, and the scale of chemical production is immense. The chemical industry produces commodities (large-volume, low-cost basic organic building blocks, such as ethylene, methanol, etc., as well as inorganics such as ammonia...

GLOBAL

FOOD SECURITY

In the 20th century, the invention of the Haber-Bosch process for converting atmospheric nitrogen into ammonia, together with the Green Revolution that dramatically improved agricultural yields, eliminated natural limits on bioavailable nitrogen and enabled an expansion...

INTEGRATING PHYSICAL AND SOCIAL SCIENCE

Replacement of conventional technologies by more sustainable versions is by no means automatic or rapid. New approaches must be cost-competitive; in manufacturing, this often means considering large existing capital investments, as well as supply risks. Changing or uncertain regulatory...

CONSERVING ENERGY

AND FRESH WATER

Many chemical industry practices are highly energy- and water-intensive. For example, the Haber-Bosch process (described above), which produces 500 million tons of ammonia-based fertilizer annually, consumes 1-2 % of the entire world energy supply. Light olefins (ethylene and propylene) are...

USING RENEWABLE RAW MATERIALS

The vast majority of synthetic carbon-based materials are currently made from a handful of petroleum-derived building blocks, including ethylene, propylene, butenes, benzene, toluene, xylene and methanol. These components are converted, using chemistry, into polymers...

REDUCING RISK THROUGHOUT THE SUPPLY CHAIN

Reduced risk of exposure and minimal environmental toxicity are important dimensions of sustainable chemistry. Cradle-to-grave life cycle assessments and fate and transport studies must be employed to quantify potential emissions of chemicals at different life cycle stages...

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