It’s no secret that cryptocurrency mining has a large carbon footprint. The process requires legions of electricity-hungry computers that work around the clock to unlock new coins by cracking math problems. Because these problems get increasingly complex over time, the system rewards energy waste: Any downtime makes the next coin harder to earn, and the only way to get an edge over competitors is to run more computers. And as the price of bitcoin rises—it was $47,318 on Sept. 19, below the peak above $60,000 reached in April—mining activity, and thus emissions, follows suit. The annual carbon footprint today is comparable to that of the London metro area.
But this mining system also pressures miners to run only the latest, fastest, most energy-efficient computer chips, and discard older ones. That leads to a mountain of electronic waste, according to a study published Sept. 16 in the journal Resources, Conservation, and Recycling. The average lifespan of a bitcoin mining chip is just 1.3 years, the study found, based on an analysis of the rate at which new hardware becomes available, and assuming that most miners replace their chips at that rate, a sound assumption because otherwise it’s nearly impossible to turn a profit.
As a result, at current bitcoin prices, the annual volume of e-waste from bitcoin mining globally is about 30,700 metric tons—about as much as the Netherlands produces in a year from laptops, phones, and other personal computing devices. Divided by the average number of bitcoin transactions, that means just two transactions create as much waste as a disposed iPad, said Alex de Vries, a cryptocurrency economist and the study’s lead author.
E-waste is the world’s fastest-growing waste stream, up 21% between 2014 and 2019 to 53.6 million metric tons, according to the United Nations. Less than one-fifth of that is recycled, and many of the metals and chemicals contained in e-waste are harmful to human health. Bitcoin’s growing appetite for new hardware is also contributing to the global shortage of semiconductor chips, de Vries said.
The solution to bitcoin’s e-waste footprint is the same as that of its carbon footprint: A new approach to mining that isn’t based on the idea of bigger-is-better. Ether, a competitor to bitcoin, is on the cusp of transitioning to a new mining method called proof-of-stake which is far more energy-efficient than the proof-of-work principle used by bitcoin and can be performed on regular computers. If bitcoin made a similar switch, it could dramatically cut its e-waste—but as long as prices as rising, it’s unlikely miners will want to rock the boat.