Climate-positive, high-tech metals are polluting Earth, but solutions await

The rapid development of renewable energy technologies — including wind, solar and hydropower, and the commercial success of hybrid and fully electric vehicles — are helping put the world on track to achieve a net-zero carbon economy and meet Paris climate agreement targets.

Yet these positive advances rely on a small number of “technology-critical elements,” or TCEs, rare materials whose mining, production and disposal are linked to myriad environmental problems, ranging from large-scale energy and water consumption, to serious soil, water and air pollution.

These 30 to 35 TCEs are essential to computers, consumer electronics, solar cells, wind turbines, electric cars, plus military and medical applications.

They include the platinum family of precious metals, rare-earth elements such as neodymium and scandium, and other metals such as cobalt, lithium and tungsten. What this diverse grouping has in common isn’t some shared chemistry, but rather its technological necessity and geopolitical scarcity. They especially share indispensable characteristics — the ability to store energy or form permanent magnets, for example — that make them essential for technologies that could help meet the Paris goal of limiting global warming to 2° Celsius (3.6° Fahrenheit) above pre-industrial levels.

But the reliance on TCEs to make high-tech green products puts these elements at risk of contributing to the breach of the nine planetary boundaries that demarcate habitable conditions on Earth.

Mineral extraction consumes gigantic quantities of fresh water and can pollute soil, water and air, while vast open-pit mines drive large-scale land-use change, cause deforestation and threaten biodiversity. Mining, processing and transporting minerals also uses enormous amounts of energy, generating greenhouse gas emissions. In the end, the TCEs themselves may become pollutants when released back into the environment as emissions or waste.

In the urgent rush to curb climate change, the risks posed by TCEs are being little addressed at present. But making their production truly green, and recycling them via a circular economy, is vital to Earth’s sustainable future.

Defining the TCE problem

Although most aren’t rare, TCEs are seldom found in large deposits, so they’re largely inaccessible to most living organisms. By extracting, using and discarding them widely, we are introducing them into new environments, with unknown consequences. That’s one reason TCEs are of emerging concern to scientists as novel chemical entities and potentially harmful pollutants.

Global production and release of all novel chemical entities — each posing different potential environmental threats — already exceeds the global capacity for safe assessment and monitoring, putting us outside the safe Earth operating zone for this poorly understood planetary boundary.

But even so, to meet the Paris targets, green technology implementation needs to ramp up substantially. By 2050, the global electric vehicle fleet must expand from around 1.2 million cars today to more than 950 million. Solar energy generating capacity needs to increase from 220 gigawatts (GW) to more than 7,000 GW. Total rechargeable battery capacity — needed for solar installations and electric cars — must increase from 0.5 gigawatt-hours (GWh) to more than 12,000 GWh.

Consequentially, demand for TCEs like cobalt, lithium, neodymium and dysprosium will soar; currently the market for these substances is growing by 5% annually. By 2050, demand for lithium and cobalt could increase as much as 500%, requiring 3 billion tons of minerals extracted. Rare-earth elements needed for wind turbines could see demand increase by a factor of 26.

Mining activities must surge to keep up with this need, with major impacts on the natural world. Extracting TCEs often involves clearing forest, removing mass quantities of soil and rock, and using water-polluting acids to isolate valuable elements. Devastating effects are multiplied when ores are located in highly biodiverse tropical regions, as is happening in the Venezuelan Amazon, or the Democratic Republic of the Congo, where coltan mining by armed militias has put the critically endangered Grauer’s gorilla (Gorilla beringei graueri) at high risk.

Perhaps the best-studied example of TCE mining impacts is in the Bayan’obo district of Inner Mongolia, an autonomous region of China that supplies half the world’s rare-earth elements. For decades, the Bayan’obo open-pit iron mine has also extracted niobium, lanthanum and neodymium for smartphones, electric cars and wind turbines, with local communities and ecosystems paying a heavy price.

Each metric ton of rare-earth element mined there necessitates clearing 300 square meters (3,230 square feet) of vegetation and topsoil, and releases 1,000 metric tons of contaminated wastewater and 2,000 metric tons of solid or liquid waste tailings.

Emerging contaminants

Today, elevated levels of rare-earth elements are being detected in wastewater, rivers and groundwater near mining and processing plants. Alarmingly, they’ve also been detected in urine samples of people living in Bayan’obo.

Many TCEs have well-documented toxic effects at high concentrations, putting the workers mining, processing and recycling these minerals at risk. These risks are compounded because many TCE mines are in less-industrialized nations with weak environmental and health regulations. Globally, hundreds of thousands of laborers are exposed to rare-earth elements, with occupational exposure associated with numerous possible health impacts.

In fact, the huge environmental and human health cost of mining TCEs is one factor making them geopolitically scarce. “The developed world has basically outsourced its raw materials to the developing world. It’s cheaper to produce them there and that is fundamentally because regulations are generally more lax,” explained Murray Hitzman, director of the Irish Centre for Research in Applied Geosciences (iCRAG) and an expert on mineral extraction.

A prime example of TCE-related human rights issues: cobalt mining in the Democratic Republic of Congo. Cobalt is economically important for the DRC: 10 million to 12 million people depend directly or indirectly on its mining for their livelihoods. But cobalt miners there are exposed to dangerous and noxious conditions in mines and build up elevated levels of toxic metals in their bodies. A 2016 Amnesty International report found that 15% of cobalt in the DRC comes from hand-dug, artisanal mines, where conditions are often even more hazardous and child labor common.

How dangerous are TCEs? ‘More questions than answers’

While we know some things about TCEs and their production risks, we know little about what happens to them after manufacture and disposal. This is partly because their meteoric rise to global importance has left scientists and policymakers playing catch-up, and partly because of the “ultra-trace” concentrations in which they’re used, making tracking challenging.

One exception: the platinum-group elements (PGEs), widely used since the 1970s to reduce vehicle exhaust emissions. PGEs are essential to catalytic converters, which have been required for new motor vehicles in the U.S., Canada, the EU and Australia for decades. These PGEs, which include palladium, platinum and rhodium, react with and remove toxic gases like carbon monoxide and nitrogen oxide from exhausts. But modern gasoline-powered cars now emit PGEs as a byproduct. These fine particulates disperse and can travel large distances in the atmosphere before settling to earth, where they can be washed away by rainwater, entering rivers, estuaries and oceans.

Platinum-group particles are now found at elevated levels in urban air, road dust, roadside soil and vegetation, and even in remote sites far from human activity. One study detected a rise in PGE levels on the Greenland ice sheet after 1990, and estimated that PGEs were being deposited there at 600 times the background rate.

Most other TCEs have not yet become as ubiquitous as the platinum family, with their environmental pathways likely quite different. Take consumer electronics, for example, which contain tiny quantities of cobalt, lithium, neodymium, indium, niobium and other TCEs, embedded with other materials like silicon and plastic. These TCEs may be released as aerosol particulates when waste is crushed or burned, or leach from landfills into soil and groundwater; but we simply don’t know for sure as the research hasn’t been done.

Research led by Brian Berkowitz and Ishai Dror at Israel’s Weizmann Institute of Science suggests rare-earth elements trapped inside e-waste are relatively immobile, and if they make their way into soil, they’re likely to stay put. In lab experiments on soil, rare-earth elements “are not very mobile — you have to work really hard to get them to move,” Berkowitz said, adding, “the good news is that they really don’t pollute the groundwater, the bad news is they’re in the soil forever.”

Some industries will be bigger sources of rare-earth element pollution than others. Along Germany’s heavily industrialized Rhine River, for example, potentially toxic levels of gadolinium, lanthanum and samarium were detected downstream of an industrial effluent pipe, although the exact source remains unclear. A 2019 study found elevated levels of rare-earth elements, including praseodymium, neodymium, dysprosium and holmium in the Pearl River Estuary in China — partly attributable to upstream e-waste recycling facilities.

Whether it’s coming from industry, from e-waste, or another source, rare-earth elements have now been detected at trace levels in a broad range of environments, in human drinking water and food.

The word trace is key here: Away from mines and recycling facilities, rare-earth elements are released at extremely low concentrations — so low that scientists are sti