It seems obvious: if we use up our resources, we will have no more resources to use. You can’t have your cake and eat it, as the old saying goes. Nowhere does this truism seem to be truer than in the realm of modern technology where mass production of almost disposable electronic gadgets from smart phones to portable chargers, tablet PC and other devices are gorging on rare metallic elements at a high speed.
In the past, humanity has found workarounds for nature’s deficits, but there are limits. There are also political and geographical constraints where demand requires access to not only rare resources but access in parts of the world that are reluctant to disseminate those resources. Crude oil is perhaps the case in point, but there are dozens of metals and metalloids that are used in essential materials and components of a wide range of devices on which modern life seems now to depend. A recent study from researchers at the Yale School of Forestry & Environmental Studies (F&ES) but some figures to this fact of technological life.
Barbara Reck and her colleagues carried out a detailed evaluation of the 62 metals and metalloids present on Periodic Table of the Elements that are all used to different degrees in consumer products. They investigated how easily it would be for us to usurp any given material in current technology and replace it with something more common if reserves of any given element dwindle or supplies become unreliable. In cookery if you lack one ingredient another will often substitute quite well. No lemons, then oranges should suffice, turmeric can often take the place of saffron and yoghurt will often suffice if you have no sour cream. There are some substitutions that simply don’t; you really cannot substitute horse radish for milk chocolate or chicken stock for custard.
Unfortunately, the Yale assessment published in a December issue of the Proceedings of the National Academy of Sciences does not bode well for a future cooked up and replete with shiny new gadgets in holiday seasons to come. They show that not one metal nor metalloid has an "exemplary" substitute for all of its major uses. There are numerous substitutions that would be like swapping anchovies for honey. They just won’t work. Moreover, for a dozen metals, such as copper, chromium, manganese, and lead, potential substitutes for each of their primary uses are either inadequate or do not exist at all. The team suggests that this dearth of substitutes underpins growing concerns among some materials scientists and others that we must not only urgently manage current resources, finding ways to reduce requirements and recycling waste more effectively, but we must also look to developing substitutes for the technology itself that will work with alternative, less rare materials.
"We all like our gadgets; we all like our smart phones. But in 20 or 30 years, will we still have access to all the elements necessary to provide the particular functions that make a smart phone so great?" asks Reck. "Based on our findings, it is unlikely that substitution can solve the supply restrictions for any of the metals on the periodic table." The team had expected to find completely substitutable elements, but the likes of the superalloy metal rhenium, used in turbine components and radiation screens, catalytic rhodium, neodymium, praseodymium, dysprosium, and terbium, used in permanent magnets have no alternatives. Similarly, lanthanum, europium, ytterbium, yttrium, strontium, and thallium have no substitutes in various of their specialist applications. If we do not find ways to carry out the same functions with alternative metals we are writing a recipe for technological disaster.
Graedel, T.E., E.M. Harper, N. Nassar, and B.K. Reck. "On the Materials Basis of Modern Society", Proc Natl Acad Sci, 2013, in press; DOI: 10.1073/pnas.1312752110