Critical materials are resources that are vulnerable to supply disruptions, where those disruptions can have significant adverse impacts on society. In the coming years, materials supply risks associated with the energy transition and geopolitics are likely to intensify and new risks are expected to emerge. This perspective identifies three "Grand Challenges"that represent frontier areas for critical materials research and highlights some promising new directions for each area: (1) extending visibility downstream to value-added materials beyond elemental forms; (2) quantifying the risks associated with market dynamics; and (3) developing tools to inform policy interventions. Emerging digital capabilities have the potential to play a significant role addressing long-standing limitations in data quality and access to unlock progress on these challenges. Progress in these areas can equip decision-makers across industry, government, and finance with tools to understand the complexity and uncertainty introduced by these real-world challenges.

Various technologies and strategies have been proposed to decarbonize the chemical industry. Assessing the decarbonization, environmental, and economic implications of these technologies and strategies is critical to identifying pathways to a more sustainable industrial future. This study reviews recent advancements and integration of systems analysis models, including process analysis, material flow analysis, life cycle assessment, techno-economic analysis, and machine learning. These models are categorized based on analytical methods and application scales (i.e., micro-, meso-, and macroscale) for promising decarbonization technologies (e.g., carbon capture, storage, and utilization, biomass feedstock, and electrification) and circular economy strategies. Incorporating forward-looking, data-driven approaches into existing models allows for optimizing complex industrial systems and assessing future impacts. Although advances in industrial ecology–, economic-, and planetary boundary–based modeling support a more holistic systems-level assessment, more efforts are needed to consider impacts on ecosystems. Effective applications of these advanced, integrated models require cross-disciplinary collaborations across chemical engineering, industrial ecology, and economics.

The deployment of renewable energy generation technologies, driven primarily by concerns over catastrophic climate change, is expected to increase rapidly in the United States. Rapid increases in the deployment of wind and solar energy will translate to increases in critical material requirements, causing concern that demand could outstrip supply, leading to mineral price volatility and potentially slowing the energy transition. This study presents a detailed demand-side model for wind and solar in the United States using dynamic material flow analysis to calculate the requirements for 15 elements: Cr, Zn, Ga, Se, Mo, Ag, Cd, In, Sn, Te, Pr, Nd, Tb, Dy, and Pb. Results show that transitioning to a completely decarbonized US energy system by 2050 could require a five-to-sevenfold increase in critical material flow-into-use compared with business as usual (BAU), with some materials requiring much larger increases. Rare earth elements (REEs) could require 60–300 times greater material flows into the US power sector in 2050 than in 2021, representing 13

Modern technology relies on an undisrupted supply of metals, yet many metals have limited geological deposits. Recovering metals from wastewater and brine could augment metal stocks, but there is little guidance on which metals to prioritize for recovery or on the techno-economic viability of extraction processes. Here we critically assess the potential for recovering metals from wastewater and brine. We first look at which metals are critical for recovery on the basis of their supply risks and the impacts of those supply restrictions. We then assess the feasibility of recovering these metals from various water sources by estimating the required operational costs to match market prices. Next we discuss the limitations of established separation technologies that may inhibit the practicality and scalability of metal recovery from water. We conclude by highlighting materials and processes that could serve as more sustainable alternatives to metal recovery with further research and development. Recovering metals from wastewater and brine could augment metal stocks that are fundamental to modern technology. This Perspective assesses the potential of, and provides guidance for, recovering metals from wastewater and brine.

Cobalt is an element in high demand for products manufactured and used in the United States. However, a detailed estimation of future cobalt needs under different conditions for specific product groups is still lacking. In the present work, we build upon the Shared Socioeconomic Pathways scenarios such that they address cobalt demand, use, recycling, and loss in the United States from 2020 to 2050. We find that cobalt demand depends strongly on energy storage (highly dependent on electric vehicles) and superalloys (highly dependent on international air travel). If the United States were to substitute cobalt in batteries and superalloys with alternative materials and, at the same time, set up efficient battery recycling programs, it could eventually recover more cobalt than it needs, allowing potential cobalt sales to other countries.

Vanadium is an element that is little known except to those who manufacture high-performance iron alloys and other widely used metal products that are indispensable for creating improved product performance across a variety of final-use sectors. We report here on deriving a detailed material flow cycle for vanadium in the United States for 1992-2021, the most recent year for which detailed data are available. The steels [tool steel, alloy steels, and high-strength low-alloy (HSLA) steels] are responsible for about half of the cumulative vanadium demand (167 Gg), with significantly smaller fractions being used to create catalysts, titanium-vanadium alloys, and several smaller product groups. These products flow to five end-use sectors, transport (61 Gg) and industrial machinery (62 Gg) being the largest. At end of product life, the vanadium-containing tool steels and catalysts are largely recycled, while most of the vanadium in carbon steels, alloy steels, HSLA steels, and other vanadium use sectors is functionally lost.

Paul Crutzen received his doctorate in meteorology from the University of Stockholm in 1968 and was awarded the Nobel Prize in Chemistry in 1995. In addition to chemistry and atmospheric science, however, the breadth of his accomplishments has also been recognized by biologists, Earth system scientists, and geologists. This tribute provides some insight into Crutzen's career and how it contributed to so many scientific disciplines. In addition, we offer a road map showing how these diverse contributions were woven together over the course of more than five decades of research. The citation for the 1995 Nobel Prize reads that it was given for "work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone." The inclusion of the wording "formation horizontal ellipsis of ozone" applies only to him among the three laureates (Crutzen, Mario Molina, and F. Sherwood Rowland). His research on tropospheric chemistry led to seminal studies of tropical biomass burning, which eventually evolved into the concept later known as "nuclear winter," a topic in the forefront of far-ranging popular discussions in the 1980s. Last, Crutzen's proposal for the emergence of the "Anthropocene" as a new geological epoch that would terminate the 11,700-yr-old Holocene is considered by the Earth system science community to be the most pronounced trademark of his remarkable career. Crutzen also received American Meteorological Society's Battan Award for his coauthorship of Atmosphere, Climate, and Change, recognized by the organization as the best book for general audiences. In the later years of his career, as a member of the Pontifical Academy of Sciences, Crutzen was a key player in the formulation of Laudato Si', Pope Francis's encyclical on climate change, which was released in advance of the Conference of Parties (COP 21) meeting that announced the formulation of the Paris Climate Accords in 2015.

One of the most unfortunate attributes of technology’s routine and widespread use of most of the elements in the periodic table is the abysmal functional recycling rates that result from the complexity of modern technology and the rudimentary technological state of the recycling industry. In this work, we demonstrate that the vast profusion of alloys, and the complexities and miniaturization of modern electronics, render functional recycling almost impossible. This situation is particularly true of “spice metals”: metals employed at very low concentrations to realize modest performance improvements in advanced alloys or complex electronics such as smartphones or laptops. Here, we present a formal definition of spice metals and explore the significant challenges that product design decisions impose on the recycling industry. We thereby identify nine spice metals: scandium (Sc), vanadium (V), gallium (Ga), arsenic (As), niobium (Nb), antimony (Sb), tellurium (Te), erbium (Er), and hafnium (Hf). These metals are considered fundamental for the properties they provide, yet they are rarely recycled. Their routine use poses severe problems for the implementation of closed material loops and the circular economy. Based on the data and discussions in this paper, we recommend that spice metals be employed only where their use will result in a highly significant improvement, and that product designers place a strong emphasis on enabling the functional recycling of these metals after their first use.

We present a material flow and stock analysis for cobalt use and waste in the United States from 1996 to 2020, including the separation of cobalt flows into six product groups and five end-use sectors. The results demonstrate the importance of U.S. manufacturing for air travel, energy storage, cemented carbides, and numerous other applications. Battery use in the United States has become the primary factor in cobalt demand, but the batteries are manufactured mainly elsewhere. The correlation of cobalt products to principal end-use sectors provides an informed view of the location of cobalt in in-use stocks. Two approaches could primarily address these stocks: enhanced recycling of batteries in consumer/business electronics and implementing cobalt-free substitutes for chemical uses and future battery technologies. Overall, cobalt's uses are as diverse and societally crucial as any element in the periodic table but have heretofore not received the levels of attention they deserve.

Materials scientists employ metals and alloys that involve most of the periodic table. Nonetheless, materials scientists rarely take material criticality and reuse potential into account. In this work, we expand upon lists of "critical materials" generated by national and regional governments by showing that many materials are employed predominantly as alloying elements, which can be a deterrent to recovery and reuse at end of product life and, likely as a consequence, have low functional end-of-life recycling rates, among other problematic characteristics. We thereby single out six metals for enhanced concern: dysprosium, samarium, vanadium, niobium, tellurium, and gallium. From that perspective, the use of critical metals in low concentrations in alloys unlikely to be routinely recycled should be avoided if possible. If not, provision should be made for better identification and more efficient recycling so that materials designated as critical can have increased potential for more than a single functional use.

The accelerating pace of resource consumption threatens long-term availability of critical materials: those resources that play an essential role in modern society but are vulnerable to supply chain disruptions. Established resource management strategies have struggled to reduce the risks of metal criticality, and the demand for these materials continues to grow. Circular economy offers a new paradigm for addressing metal criticality through solutions that enable material and product reuse, remanufacturing, and recycling. However, products containing critical materials are rarely designed to be upgraded, reused, or disassembled at end of life to access the valuable materials contained within. Here, we explore the potential for design interventions across the technology life cycle that can enable circular economy solutions and minimize risks of material criticality.

Given increasing concerns for the marine environment and human health, as well as trade restrictions from Asian countries, plastics have become a great challenge for the United States. This study addresses the seven commonly used plastics: low-density polyethylene/linear low-density polyethylene, high-density polyethylene, polyethylene terephthalate (PET), polypropylene, polystyrene, polyvinyl chloride, and other plastics. Material flows of the seven polymers were tracked from production into fabrication, manufacturing, flow into use, waste management, and recycling in the United States in 2015. Low- and high-density polyethylene and polypropylene were found to be the largest in both production and product manufacture. More than 88% of the plastics went into three end-use sectors: Packaging, Consumer and Institutional Products, and Building and Construction. In-use lifetimes across the plastics are generally short. Virgin plastics were mainly exported, while intermediate plastic products were largely imported. The actual end-of-life recycling rate of the plastics as a group was no more than 6.2%, with PET and the polyethylene family the most recycled. The high yearly plastic throughput and low recycling rate pose a serious challenge to the sustainability goals of the United States and is in stark contrast to the vision of a circular economy of plastics.

Materials today are often discarded after their first use. This is especially true of those materials in uses that are inherently dissipative, in complex assemblages where elements in low but vital concentrations are often lost in recycling, and for useful but toxic materials. The status of reuse and recycling as well as five opportunities for improvement are presented: (1) eliminate dissipative uses of materials; (2) develop advanced technologies for reuse and recycling; (3) create suitable repositories for materials unsuitable for a circular economy; (4) Design new products for circularity at end of life; (5) create and support international collaborative shipping and recycling chains.

During the 20th century, the United States went from being the largest producer and user of lithium to being heavily reliant on imports from Asia, particularly lithium-ion batteries. To explore different futures for U.S. lithium, we here generate four scenarios─including COVID-19 implications─that model lithium use for its main applications: electric and hybrid vehicles, stationary energy storage systems, and small electronics. We find that the "Sustainable Future" scenario requires the highest amount of lithium (cumulatively 1281 Gg in the period 2020-2050, peak inflow in 2040 at 53 Gg); in contrast, "Fossil Fuel Everything" requires only 500 Gg and peaks in 2050 at 26 Gg. COVID-19 implications appear to be negligible in the long run. The future electrification of the U.S. vehicle fleet and energy storage systems will depend upon a reliable and resilient international supply chain of lithium chemicals and/or batteries as well as vigorous recycling efforts.

Clay brick masonry is a vernacular construction technique; it continues to be used extensively in Italy and elsewhere. Despite the essential role clay bricks play in construction, they are often overlooked in the environmental literature, and sound production data are hard to obtain. This study integrates material flow analysis (MFA) and building information modeling (BIM) to assess the quantity and use cases of clay bricks and terracotta tiles used for construction in Italy. Material flows for these products were traced from the supply of raw materials to manufacturing, use, demolition, and waste management in Italy in 2006, 2011, and 2016. 3D representations of typical buildings were drawn in BIM and used to create material intensities to investigate functional uses of bricks. Hollow bricks used as infills in external walls and load-bearing bricks were the main products manufactured in all three years of analysis, followed by bricks used in internal walls and floor-forming bricks. In all cases, maintenance and refurbishment of existing buildings was the primary end-use category. From 2006 to 2016, the Italian brick production shrank fourfold, from 20.6 Tg to 5.1 Tg, while direct carbon dioxide emissions from the calcination of calcium carbonate decreased from 2.4 Tg to 0.5 Tg. Functional recycling is rare, and this poses serious challenges to the circularity of the construction sector. The results demonstrate that the integration of MFA and BIM approaches markedly improves the detail, speed, and realism of quantifying the material flows within the urban environment. This article met the requirements for a Gold-Gold JIE data openness badge described at http://jie.click/badges..

The Hawaiian Islands form a holarchic system with at least five nested layers (holons) at increasing spatial scales: from a single enterprise to cities, to individual islands, to the archipelago (the group of islands), and to the global resource base that connects them all. Each holonic layer operates individually but is also linked to holons at lower and higher levels by material input and output flows. An integrated study of the holarchic system allows us to explore the value of applying this concept to industrial ecology. We present examples from a multi-level material flow analysis combining a large quantity of material and energy flow data for Hawaii from the five holarchic levels. Our analysis demonstrates how a holarchic approach to the study of selected interacting systems can reveal features and linkages of their metabolism not otherwise apparent and can provide a novel basis for discovering material, energy, and societal connections.

Over the past century lithium went from being a minor metal with very limited application to being one of the core elements for the electrification revolution of the automotive sector. In spite of, or perhaps because of its strategic importance in many industrial fields, lithium extraction and trade has historically been underreported. This research aims to provide a clear analysis and data for lithium extraction and trade in the United States, which was, until a few decades ago, both the largest lithium producer and end-user in the world. The analysis covers the period 1910–2016, and reports lithium flows for the mining, chemical, and end-use sectors. The data show that lithium extraction in the United States peaked in 1974 (5.0 Gg), decreasing to 1.1 Gg by 2016, and that U.S. trade of lithium ores and brines is nearly non-existent. In the chemical sector, domestic use has remained relatively constant since the 1950′s (2.3 Gg), while exports have been significant since the 1980′s (1.8 Gg year⁻1 on average). Imports became of critical importance in 1998, with the closure of the last domestic lithium mine. The end-use sector has grown over time, reaching 6.5 Gg in 2016, and is now dominated by lithium used in batteries (2.8 Gg). Except for batteries, there appears to be little potential for lithium recovery and reuse.

Copper is widely used in modern technology, but declining ore grades and depletion of natural deposits have raised concerns regarding sustainable demand-supply balance in the long term. The vulnerability to primary copper supply restrictions amplifies for countries dependant on imports, notably many EU Member States. Recycling of post-consumer scrap can provide a valuable source of essential material to the European industry. However, a considerable fraction of collected and processed copper old scrap is exported, while the remaining fraction is either not recovered or lost due to nonfunctional recycling undermining the implementation of a circular economy. In this work, material flow analysis, regression analysis, and life cycle assessment are combined to explore the possible evolution of four scenarios of copper demand in Europe to year 2050 and the potentials for greenhouse gas emissions reduction under material circularity conditions. The results show that for three of the four scenarios, secondary production would not comply with the carbon dioxide emissions reduction target of 50% below 2000 levels neither in case of combined aggressive recycling, moderate decarbonization of electricity, and energy efficiency improvements. In particular, for the scenario that describes a "business as usual" approach, the modelled future domestic demand can only be met by increasing primary inputs and, despite strong efforts to improve recycling at end-of-life, the fraction of old scrap in total metal demand seems likely to achieve 65% at best. Should that scenario ensue, the GHG emissions embodied in EU copper demand might result in an emissions gap of more than 15 TgCO(2) eq or about + 260% the carbon dioxide reduction target. In contrast, the lowest environmental impacts are associated with a scenario emphasizing green technology and more equitable lifestyles. In that scenario, the secondary copper flows will gradually approach the expected demand, laying the foundation for achieving a circular economy with considerable potential for preserving natural capital and mitigating climate change. This possible future, however, requires dramatic changes in the current pattern of material production and consumption, as we discuss.

Tungsten is deemed a critical raw material by many nations, given its irreplaceable use in industrial and military applications. In particular, much concern has been drawn to China's high share in global tungsten supply. While various studies have focused on the criticality of tungsten, few have specifically explored how tungsten is produced, consumed, and traded. In this paper, the dynamic material flow analysis is applied to quantify China's annual tungsten cycle from 1949 - 2017. It is estimated that total tungsten mined from ores in China over the past 68-year period is similar to 2500 kilo-tons (kt). Among those, similar to 750 kt of tungsten has been exported to other countries, and around 970 kt tungsten is domestically consumed. It is noted approximate to 1720 kt has been lost from mining, production, and end-of-life stage, and merely similar to 130 kt has been recycled as end-of-life scrap. Our material flow analysis further refined China's tungsten dominance. Although China currently dominates the global production of tungsten, this dominance will not extend too far into the future given China's limited share of world tungsten reserves and its declining ore quality. Our trade flow analysis reveals that China imported 35 kt of high valueadded downstream tungsten products from outside manufacturers, whose mineral resource was originally imported from China. At present, China by itself is experiencing overcapacity issues in the primary production, which discourages the recycling of at end-of-life (EoL) stage and makes the EoL recycling rate only 10%. It is noted that the percentage of Chinese tungsten for domestic consumption has been increasing in the past few years. This highlights the need for systematic measures from stakeholders along the tungsten cycle to promote sustainable practices for efficient tungsten production, use, and recycling in China. Meanwhile, the results also suggest the importance of monitoring the criticality of tungsten and other critical minerals from a dynamic and material cycle perspective.