Smartphone

A smartphone contains something in the region of sixty of the ninety or so elements that occur usefully in nature. No other object in ordinary use comes close, and the count is not padding — each one is there because nothing else does its job.

A rough inventory by function. Structure: an aluminium alloy frame or a glass and polymer body, and an aluminosilicate cover glass chemically strengthened by ion exchange. Processor: silicon, with copper interconnect, tungsten vias, cobalt and hafnium in the transistor structures, and a dozen dopants at parts per billion. Display: indium tin oxide for the transparent electrode, and rare earths in the emitters. Battery: lithium, cobalt, graphite, aluminium, copper. Speakers and vibration motor: neodymium, iron, boron, and dysprosium to keep the magnet working when it warms. Capacitors: tantalum, in quantities so small and so essential that the metal became a conflict-minerals category of its own. Circuit board: copper, glass fibre, epoxy, tin, silver, gold.

The gold is worth noting for scale. There is roughly thirty milligrams of it in a phone — pennies' worth — and it is there because gold does not corrode, so a contact plated with it still works in ten years. A tonne of phones contains far more gold than a tonne of ore from any mine on earth.

Almost every material in a phone is present because of a property that only becomes visible at small scale or long duration.

The cover glass is soda-lime's chemistry with the sodium swapped for potassium at the surface. Potassium ions are larger, so the surface layer is left in compression, and a crack cannot open against compression. That is why a phone screen survives being sat on and shatters when dropped on a corner — a point load reaches past the compressed layer.

The magnets are neodymium-iron-boron with a few per cent of dysprosium or terbium, and the heavy rare earth is there for one reason: coercivity falls with temperature, and a magnet next to a warm processor would otherwise weaken. Perhaps a gram of it, and it is the part of the phone with the sharpest supply concentration.

The capacitors exploit tantalum's oxide, which forms a coherent insulating film only nanometres thick that will hold hundreds of times its own thickness in voltage. That gives more capacitance per cubic millimetre than any competing chemistry, which is why the metal survives in an application where everything else has been miniaturised away.

The battery is the only part of the phone that is consumed rather than used, and it sets the object's life. Everything else would work for decades.

The phone is where four separate raw-material arguments meet, and they are worth separating.

Conflict minerals. Tin, tantalum, tungsten and gold — the 3TG — were the subject of the first serious supply-chain due diligence regime in electronics, driven by armed groups financing themselves from mining in eastern Congo. Section 1502 of Dodd-Frank in 2010 and the EU regulation that followed made smelter-level auditing routine. It is one of the few such regimes with measurable effect and it did not solve the problem.

Cobalt, for the battery, carries the artisanal mining problem that no audit has been able to close.

Rare earths, for the magnets and phosphors, carry a processing concentration rather than a mining one — separation is the hard step and it is overwhelmingly Chinese.

Everything else is simply too dispersed to recover. The recycling arithmetic is stark: gold, silver, copper and palladium are recovered because they pay, and indium, tantalum, gallium and the rare earths mostly are not, because there are milligrams of each in a device that has to be shredded to get at any of it. Well under a fifth of electronic waste is formally recycled worldwide.

And the object's lifetime is a materials decision made elsewhere. A phone replaced after three years has amortised sixty supply chains over three years; the manufacturing footprint dominates the use footprint by a wide margin, so how long it is kept matters more than what it draws from a socket.

Roughly eighty per cent of a phone's lifetime carbon is emitted before it is switched on, which inverts the intuition that a device's footprint is about its electricity.

That is because the processor is the most energy-intensive manufactured object per gram there is. A wafer fab uses vast quantities of ultrapure water and electricity, and the yield means much of what is made is discarded.

So the honest advice is unglamorous and does not involve buying anything: keep it longer, replace the battery rather than the phone, and pass it on rather than putting it in a drawer. The estimated number of unused phones sitting in drawers worldwide runs into the billions, which is a larger stock of recoverable metal than most mines represent — and it is the reason repairability and battery-replacement rules have become materials policy rather than consumer policy.