The earth is finite and so are the chemical elements of which it is composed. Those elements, represented by the symbols that fill the boxes of the periodic table, fuel all human consumption. Yet we are mining and redistributing these fundamental elements at such a rapid rate that many are already in short supply or likely to become so in the next few decades. To maintain supply lines to the dinner table and to industry, we must completely reframe our understanding of mining, consumption, human environments, and waste, recognizing that the accessible elemental resources of our future are largely stored aboveground in the familiar objects of our daily lives.
The situation is so critical that in a recent report of the Royal Society of Chemistry, a color-coded periodic table indicated the degree to which the basic building blocks of human consumption are now “endangered elements” (see Figure 1).1 Chemical elements are being shifted out of their natural reserves in deposits in the earth’s crust and into human consumables at a remarkable rate. As far back as 20 years ago, a study conducted at Kyoto University based on data from that time concluded that 80 percent of the world’s mercury (element number Z = 80) reserves; 75 percent of its silver (Z = 47), tin (Z = 50), and lead (Z = 82); 70 percent of gold (Z = 79) and zinc (Z = 30); and 50 percent of copper (Z = 29) and manganese (Z = 25) had already been processed through human products.2
Some of the elements under serious threat are familiar. Silver, for example, which is used as a catalyst for a wide variety of chemical reactions in manufacturing, and zinc, used to protect iron and steel against corrosion.
Other, less well-appreciated elements that form the basis of modern life are also being consumed unsustainably, including tellurium (Z = 52) and hafnium (Z = 72), both of which are used in electrical devices and special metallic alloys. Indium (Z = 49), a common ingredient of solar cells and computer displays is on the endangered list, as is neodymium (Z = 60), an important building block of magnets used in many industries (e.g., for wind turbines, car batteries, and computer hard-disk drives) as well as in ceramics and glasses.
The rapid disposal of mobile phones, laptop computers, and batteries is placing large stores of some of the rarest elements directly into the waste bin, including gold, silver, and indium. It is important to realize, however, that mining urban dumps will not provide a full solution to the endangered element dilemma. This is because most “aboveground” metals are contained in products that are actively in use by humans rather than those used for processing, manufacturing, or discarded as waste. As an example, nearly half the world’s past and current zinc reserves appear to be aboveground and in use. So changing the pattern of human consumption of elements will also need to play a role in maintaining their availability.
Unfortunately, accurate estimates of the exact amount of the elements currently in human use around the world are hindered by large gaps in our understanding. Reasonably robust global estimates do exist for the amount of in-use aluminum, lead, copper, zinc, and iron.3 Of these, lead, copper, and zinc are on the endangered list. Comparison with underground global ore reserves4 indicates that, as a fraction of all past and current such reserves, 45 percent of lead, between 33 percent and 43 percent of copper, and at least 45 percent of zinc were already aboveground and in use by 2005.
Japan’s National Institute of Material Science (NIMS) has conducted what may be the most detailed national inventory of elements in the “urban mines” of consumer products. In 2008, it estimated that discarded high-tech devices and other products in Japan alone contain a remarkable fraction of the world’s reserves of some elements. Japanese urban areas are estimated to contain 16 percent of the world’s gold, 22 percent of its silver, 15 percent of its indium, 19 percent of its antimony (Z = 51), nearly 11 percent of its tin, and more than 10 percent of its tantalum (Z = 73).5
In order to ease the increasing risk of demand outstripping supply for some of these substances, it may be possible in some cases to substitute other elements in manufacturing processes,1 though this simply pushes the problem from one spot in the periodic table of elements to another. In other cases, however, only a particular element of nature will do, as in the case of phosphorus.
Phosphorus (Z = 15) is required for living cells and is a major and essential component of agricultural fertilizers, yet some researchers predict that global phosphorus production may reach its peak as early as 2030.6 According to the Royal Society, rock phosphate reserves are likely to be exhausted in North America, northern and southern Africa, Russia, and southeast Asia before the end of this century.7 The price of the phosphate rock and two common types of phosphate fertilizer (DAP and TSP) produced from it have exhibited a sharp peak in the last decade as well as an overall increase.8 Phosphate prices and shortages are even more important given the growing and often malnourished global population. The 2009 World Food Summit estimated that a 70 percent increase in food production will be required by 2050.9
The relative scarcity of some elemental reserves relative to the expected demand in the next few decades is exacerbated by their uneven distribution across the earth’s surface. More than 75 percent of the known reserves of phosphate rock are in the hands of a single country (Morocco).10 The U.S. Government Accounting Office estimates that 97 percent of the “rare earth” oxide reserves are in China.11 China has decreased export quotas and increased export tariffs, causing shocks to industry and spurring efforts by other nations to develop alternative sources of rare earth metals.12 The reserves of many other elements are also concentrated in only a few nations.
In assessing the implications of these data, it should be remembered that the term “reserves” is generally taken to mean the identified geological source of an element or mineral that, at the specified time of the determination, could be extracted and produced economically.10 It does not imply that the facilities to do so are actually present or operational. If a new deposit is discovered and/or economic conditions change, the amount of an element “in reserve” could increase.
In fact, even though the demand for minerals increased exponentially over the last century, new technology and mining in new locations usually enabled global supply to meet demand.13 In stable periods between short-term spikes, real prices have changed little for most elements. Indeed, despite increased consumption, the reserves of most elements have remained relatively constant over the decade 1997–2007.13 The question is whether the doubling in real price since 2002 is just another short-term spike or instead represents a new trend due to the exhaustion of easy-to-access, high-grade ore mines and rapidly increasing new demand from large developing nations.
There is reason to suspect the latter. Newer geological reserves tend to have lower ore concentration and to be found in more hostile, difficult-to-access regions farther from consumers—and the consumption of elemental resources is increasing much faster than the global population.13 Between 1950 and 2000, the world’s population slightly more than doubled, while the production of precious metals grew fivefold. Between 1947 and 2000, per capita zinc consumption in the United States rose from 6.3 to 210 kilograms. For comparison, the average citizen of Cape Town, South Africa, used about 18 kilograms of zinc in 2002.3 In the future, if citizens in developing countries use metals to the same extent and in the same way as those in developed countries do now, even more metals would be stored “in use” in human products—between three and nine times more.3
The time has come for a new concept of mining to meet this burgeoning demand. For many elements, the future may lie not in single-take, geological mining but in continuous “re-mining” aboveground in the generally urban locations of our consumer products and trash dumps. We must recognize and utilize these potential “mines” that we have already created at locations aboveground, rather than placing faith in undiscovered, remote, and increasingly economically unviable resources deep beneath the earth’s surface.
However, there is a long way to travel to reach sustainable, closed-cycle use of elements. For true sustainability, all goods should be made of re-mined elements, that is, with 100 percent recycled content. In fact, only lead, ruthenium (Z = 44), and niobium (Z = 41) are found in products in re-mined fractions larger than 50 percent, though 16 other elements have re-mined fractions between 25 percent and 50 percent.14
The good news is that some industries, governments, scientists, and local communities have already begun serious programs to speed sustainable use of the natural resources catalogued in the periodic table of elements.
The chemical industry is in a key position. Chemical companies are in the business of sourcing elements and more complex chemicals in order to recombine them into innovative products that meet a wide variety of industrial needs in, for example, agriculture, construction, medicine, manufacturing, and personal-care products (such as cosmetics, shampoo, etc.). In its just-released long-term business strategy, BASF, the world’s largest diversified producer of chemicals, has indicated that it intends to use sustainability as a strategic driver for the company, in particular re-mining the rare earth elements from its own activities.15 BASF’s goal is to be a leader in chemical solutions for a sustainable world in the next decade; doing so will require stable and secure supplies of basic chemical elements.
The company 3M instituted a waste-reduction program in 1975 and has documented its progress.16 Between 1990 and 2010, 3M reduced the tonnage of waste it produced (defined primarily as unused raw materials) per sales dollar by 66 percent. The company’s strategy, which it calls “Pollution Prevention Pays,” is financially motivated, as the slogan indicates. By reformulating its products, redesigning equipment, modifying processes, and reusing and recycling waste, 3M estimates that it has prevented more than three billion pounds of pollutants and saved nearly U.S.$1.4 billion, based on the combined results of the first year of each of its individual programs.17
According to a recent study, public-private partnerships appear to be the most common policy tool used by nations to maintain the supply of element and mineral resources.13 The partnerships are used to pool resources and expertise, negotiate external contracts and acquisitions, and build national capacity. Strategic partnerships with other nations and recycling are also important for many countries. Further, efforts to increase renewable energy will reduce risk, as mineral extraction is energy-intensive and mineral prices roughly track those of crude oil. Research and development is also important, including an emphasis on efficient practices and achieving similar material characteristics with different elemental compositions.
Japan, for example, has instituted an Element Strategy Initiative based on these four pillars: (1) substitution (of an endangered element for a more readily available one), (2) regulation (to avoid shortages and chemical hazards), (3) reduction (e.g., by increasing process efficiencies in manufacturing), and (4) recovery (including recycling and urban mining).12 The initiative’s goals are to reduce the risk of shortages and increase the stock of usable ore in a nation that is otherwise poor in geological mineral resources.
Material scientists are tackling elemental substitution on many fronts. In one example, they have discovered that when common nitrogen is added appropriately to a form of carbon known as graphene, a catalyst results that could substitute for the platinum (Z = 78) catalyst currently used in clean fuel-cell vehicles.12 Within five years chemists may be able to develop a replacement for the endangered rare earth neodymium, widely used in magnets.1
Cost-effective urban mining will require a suite of new technologies as well as product redesign to allow easier separation of elements. One possibility would make use of microorganisms engineered to have increased abilities to adsorb particular metals through proteins in their cytoplasm or cell surface.18 If mixed in solution with waste, the metals can then be “harvested” by separating the microbes and then processing them to remove the trace metal. In principle, the microbial cells can then be reused to repeat the process with another batch of waste.
Citizens can contribute in a very personal way to re-mining in their local communities. Urine is phosphorus rich and a natural consequence of human food production. Two Swedish cities now require the use of toilets that separate urine from solids as a step toward realizing the Swedish government’s goal of re-mining 60 percent of the phosphorus contained in sewage by 2015.6 Doing so will obtain a source of phosphorus native to Sweden, augmenting imported phosphate rock.
Mining phosphorus from wastewater and agricultural runoff will reduce the environmental damage caused by algal blooms in downstream ecosystems. As the algae die and sink, they are decomposed by oxygen-consuming bacteria, which rob deeper animal life of oxygen. In extreme cases, fishing dead zones are created. Great scope for improvement exists, as currently only about one-quarter of agricultural phosphorus is recycled back into fields,19 with much of the rest running off, to the detriment of the environment.
Most conservation solutions can produce additional benefits beyond sustainable use of elements. Price volatility and geopolitical tensions can be reduced through a more even distribution of elements. Urban re-mining would reduce both the environmental damage caused by geological mining and the amount of landfill space required for discarded goods. A cost-effective substitute for endangered elements currently used in the batteries of clean vehicles would reduce the greenhouse gas emissions associated with transportation.
Effective strategies to achieve elemental sustainability and concomitant benefits will require a systems approach that examines all facets of the consumer cycle as well as market and nonmarket approaches to properly account for the true, full value of linked element-energy-environment resource use.20
First steps can be taken now by
- taking better stock of the rich veins of chemical elements tied up in our consumer goods and discarded into waste streams;
- reducing unnecessary consumption;
- increasing the efficiency with which we use the most endangered elements;
- substituting into consumer goods elements that are more readily available and more easily re-mined;
- improving the efficiency of reextraction of the elements from urban mines;
- designing and engineering for a closed life cycle of elements—extraction, production, consumption, and reextraction for further reuse; and
- developing new relationships between suppliers (re-miners), producers, manufacturers, and consumers to effectively transport material from those who see it as waste to those who see it as a resource.
But perhaps most importantly, achieving sustainable use of the elements will require re-visioning our interaction with rural and urban environments, our concept of mining, and our attitudes toward waste. Consumption will need to be seen as a continuous cycle: a cycle with no off-ramps for trash, junk, or waste. What we now call our possessions, our homes, our cities, our soil, our organic waste, and urban scrap heaps are not (permanent) ends, but very literally the means to the next cycle of human consumption—the banks that hold our globally shared reserves of precious chemical elements.