TO GLIMPSE A potentially troubling side of the clean-energy business, look at the giant Anglo-Swiss oil-trading firms. They are betting on a scramble for battery materials to power electric vehicles.

Glencore, one of the world’s biggest commodities companies, plans to double its production of cobalt by 2020, which it reckons will give it 40% of the market. Cobalt is an important raw material for lithium-ion batteries, found mostly in the Democratic Republic of Congo (DRC). But Saad Rahim, chief economist of Trafigura, a rival, says battery producers will use more nickel and less cobalt in nickel-manganese-cobalt cathodes to avoid dealing with the DRC, which has a tainted reputation. Last year Trafigura agreed to spend $200m funding a nickel mine in pristine Finland.

America produces few of the minerals it needs for renewables. In December President Donald Trump issued an executive order to speed the search for new sources of minerals at home. America relies on imports for 70% of its lithium, and on imports and releases from the National Defence Stockpile for 75-80% of its cobalt.

In an accompanying report, the United States Geological Survey (USGS) said that America’s dependence on imported minerals had soared since the 1970s and that China produces 85% of the world’s rare earths, used extensively in renewable-energy applications such as wind turbines. The USGS also identified China as the main producer of minerals such as germanium and indium, used for solar power, and graphite, used in fuel cells and batteries; and as the world’s largest refiner of cobalt, using material mostly from the DRC.

There is no risk that these resources will run out. Deposits of lithium, for example, are thought to be 3,000 times current annual output. But their supply could be manipulated for political ends. In 2010 China drastically cut its export quotas for rare earths, leaving the world scrambling for alternatives. The curbs were lifted in 2015.

These minerals are scarce only because deposits in other parts of the world have so far been uneconomic to extract, but that may change as demand for transparently sourced minerals increases. In Australia investment in battery minerals such as lithium and cobalt is already booming.

In America domestic supplies will depend largely on investors’ appetite for putting their money into materials with extraordinarily volatile prices. The country’s only functioning rare-earths mine, Mountain Pass in California, went bankrupt in 2015 as prices plunged. It has since been bought out by a consortium led by, of all things, a Chinese rare-earth producer.