Extracting a dollar value of cryptocurrency as bitcoins from the deep Web consumes three times more energy than digging a gold dollar, the researchers said on Monday.
Now there are hundreds of virtual currencies and an unknown number of server farms all over the world that run all day to bring them to light, more than half in China, according to a recent report from the University of Cambridge.
Virtual currencies extracted with real value, in other words, entail a hidden environmental cost that is rarely measured or taken into account.
"Now we have a completely new industry that consumes more energy in the year than many countries," said Max Krause, a researcher at the Oak Ridge Institute for Science and Education, and lead author of the study published in Sustainability of nature.
"In 2018, the bitcoin is on track to consume more energy than Denmark," he said AFP.
Denmark consumed 31.4 billion kilowatt hours of electricity in 2015. Starting from 1 July of this year, the Bitcoin mining sector used around 30.1 billion kilowatt-hours, according to the study.
The highly competitive practice of mining cryptocurrencies requires hundreds, even tens of thousands, of connected computers that perform intensive calculations in search of the Internet's equivalent of precious metals.
The new coins are assigned to those who complete the calculations first, with the transaction confirmed and entered into the public shared ledger of the currency, known as "blockchain".
The first 100 cryptocurrencies have a current market value of about $ 200 billion (€ 175 billion), second Coinmarketcap.com.
Bitcoin accounts for more than half of this amount.
"We wanted to spread awareness about potential environmental costs for mining cryptocurrencies," said Krause.
Digital is not free of costs
"Just because you're creating a digital product, that does not mean it does not consume a lot of energy to make it".
The films, music and videos that billions of people broadcast every day all have measurable environmental costs, have shown previous research.
For the study, Krause and Thabet Tolaymat, an environmental engineer based in Cincinnati, Ohio, have calculated the average energy consumed to create a US dollar value of four major virtual currencies – bitcoin, ethereum, litecoin and monero – in the # 39 over the 30 months following June 2018.
That sum was 17, 7, 7 and 14 million joules, or megajoules (MJ), respectively.
A joule is a unit of energy equivalent to the work required to produce one watt of power for a second.
They found up to three times the energy needed to dig gold, platinum or copper. Among the metals examined, only aluminum – at 122 MJ for each dollar – was more energetic.
A complete calculation of the environmental cost of virtual currencies would take into account the computer banks used to extract them.
"Computers are made of gold and other precious metals," Krause said.
"They are managed aggressively, which means that the hardware is destroyed much more quickly than you or I would expect for regular use, maybe a year instead of five or ten."