Comment pubs.acs.org/est
From the Ontonagon Boulder to the Circular Economy
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Policies that remove institutional barriers to resource recovery or that require miners and waste dischargers to pay the full environmental costs of their actions might make resource recovery more attractive. In many countries, policy changes have already made recycling of aluminum cans and recovery of precious metals from e-waste viable. Nonetheless, substantial technological advances are still needed to close the resource loop, especially for dilute waste streams. Our community can play an important role in turning wastes into resources by tapping into the latest technological developments for resource extraction and pollution control. For example, in response to concerns about the security of nuclear fuel stocks, the governments of China, Japan, and the United States have embarked on ambitious programs to obtain uranium from seawater. Over the past few years, governmentfunded researchers have developed selective ligands and floating strands of recoverable resins that can extract uranium, which is present at a concentration of about 3 μg/L, from seawater at a cost that is within reach of the market price. The recovery of precious metals from concentrate streams produced by seawater desalination plants also has been proposed as a means of offsetting the high costs of plant operations. Ligands capable of pulling trace elements out of seawater also could be used to extract metals from diffuse waste streams, such as municipal wastewater effluent, landfill leachate and industrial process water. Technologies to immobilize pollutants in contaminated surface- and groundwater also could be repurposed for resource recovery. Current efforts to decontaminate the area around the Fukushima Diaichi nuclear power plant are spurring the development of geomaterials that can effectively sequester 137 Cs. Similarly, limnologists and engineers grappling with the challenge of nonpoint pollution have employed whole lake treatment with geomaterials, such as lanthanum-functionalized clays, to hold phosphate in sediments. As our community creates new materials for sequestering pollutants, we should take the extra step of developing the means to recover and reuse the spent media. Creative researchers could undoubtedly employ enzymes, electrochemistry and other tools of our trade to recover critical elements from dilute waste streams, but funding opportunities are still limited. Therefore, a sustained effort is needed to enable this aspect of society’s transition to a circular economy. In the early years, many of the technologies that we develop might be most applicable to pollution control and recovery of resources from concentrated waste streams. But in the long term, new approaches for recovering critical elements from dilute sources may prove to be integral to prosperity on a planet that does not contain any more Ontonagon Boulders.
omewhere in a storage room at the Smithsonian Institution’s Natural History Museum sits the Ontonagon Bouldera 1680 kg piece of pure copper that was carted from Michigan’s Upper Peninsula to Washington DC over 150 years ago. Although it is unusual, this specimen is hardly unique. During prehistoric times, hunks of copper, iron, and flint were routinely found in rock outcroppings or just under the ground surface. After our ancestors recognized the useful properties of these distinctive objects, they developed trade routes and manufactured tools and weapons of increasing sophistication. Metallurgy, which was the high-tech industry of the Copper and Bronze Ages, advanced civilization and fostered interest in understanding how the world worked. As living standards improved from application of knowledge about metallurgy, agriculture, and related topics, easily accessible sources of pure elements and minerals were depleted. Responding to shortages, metallurgists developed a means of smelting iron ores, which were much more abundant than copper and tin. To fulfill the demand for less common minerals, early engineers developed mining techniques capable of accessing mineral deposits hidden deep below the earth’s surface. Equipped with these new technologies, the quest for rare minerals hastened the settlement of the Americas and Australia. Mining also increased crop productivity as Chilean caliche (a nitrate-containing mineral) and guano were exploited by farmers struggling to meet the needs of growing populations solely through the use of animal waste. As we adjust to the Anthropocene, population growth and increasing standards of living are again raising the prospect that we will experience shortages of mineral resources. Recognizing the need to transition to a more sustainable way of life, enlightened policymakers have begun to get serious about creating a circular economy in which renewable materials replace finite mineral resources and those products that require rare elements are reused or recycled. Although the need to make this transition is obvious, progress is likely to be slow because the cost of recovering most nonrenewable resources is considerably higher than that of virgin mineral deposits. For example, the cost of recovering phosphorus from municipal wastewater is typically 5−10 times higher than the going price of mined phosphate. If we simply wait for shortages to tip the balance to a point where recovery makes economic sense, we may deplete reserves needed by future generations in applications for which no good substitutes are available. Given the current rate of global economic development, it would be unwise to ignore potential risks of shortages or become too reliant on sources of minerals that are susceptible to supply disruptions. The nascent field of material criticality assesses these risks and provides decision-makers with guidance about which squares on the periodic table might prove to be vulnerable in the coming decades. Although we can use this approach to anticipate the risks of overreliance on a specific resource, we cannot overcome the fact that waste is material from which resource recovery is economically unfavorable. © 2017 American Chemical Society
David Sedlak, Editor-in-Chief Published: February 1, 2017 1941
DOI: 10.1021/acs.est.7b00430 Environ. Sci. Technol. 2017, 51, 1941−1942
Comment
Environmental Science & Technology
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AUTHOR INFORMATION
Notes
Views expressed in this editorial are those of the author and not necessarily the views of the ACS. The author declares no competing financial interest.
1942
DOI: 10.1021/acs.est.7b00430 Environ. Sci. Technol. 2017, 51, 1941−1942
