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When Chris Precht, an Austrian architect and artist, first learned about nonfungible tokens, the digital collectibles taking the art world by storm, he was so enthralled, he said, he "felt like a little kid again."

So Precht, who is known for his work on ecological architecture, was devastated to learn that the artworks, known as NFTs, have an environmental footprint as mind-boggling as the gold-rush frenzy they've whipped up.

"The numbers are just crushing," he said from his studio in Pfarrwerfen, Austria, announcing that he was canceling his plans, one of a growing number of artists who are swearing off NFTs. "As much as it hurts financially and mentally, I can't."

Financially, for sure. Last month, a montage of art that had been turned into an NFT by digital artist Beeple sold for more than $69 million at a Christie's online auction.

But, by Precht's calculations, creating the 300 items of digital art that he had planned to sell — 100 each of three art pieces — would have burned through the same amount of electricity that an average European would otherwise use in two decades, he said late last month.

What in the (warming) world?

An NFT is a piece of artwork stamped with a string of code and stored on a virtual ledger called a blockchain. But blockchain technology, which also forms the basis of cryptocurrencies like Bitcoin, comes with enormous greenhouse-gas emissions.

In a nutshell, when an artist uploads a piece of art and clicks a button to "mint" it, she or he starts a process known as mining, which involves complex puzzles, awesome computing power and a huge load of energy. That's because Ethereum, the platform of choice for NFTs, uses a method called proof of work to create digital assets like nonfungible tokens.

To successfully add an asset to the blockchain's master ledger, miners must compete to solve a cryptographic puzzle, their computers generating numbers in a frenzied race of trial and error. As of mid-April, miners were making more than 170 quintillion attempts a second to produce new blocks, according to the trading platform (A quintillion is 1 followed by 18 zeros.)

The miner who arrives at the right answer first is the winner, and gets her or his asset added to the blockchain.

The system is intentionally designed to be onerous, ostensibly to make it transparent and competitive, and to prevent cheating. Bitcoin, the largest cryptocurrency, also uses the energy intensive proof-of-work model.

According to an estimate backed up by independent researchers, the creation of an average NFT has a stunning environmental footprint of more than 200 kilograms of planet-warming carbon, equivalent to driving 500 miles in a typical American gasoline-powered car.

Researchers at Cambridge University have estimated that mining Bitcoin uses more electricity than entire countries like Argentina, Sweden or Pakistan. A paper in the journal Nature Communications warned that, if left unchecked, cryptomining in China could undercut the nation's climate goals.

"I know it's difficult to comprehend," said Susanne Köhler, an expert in life cycle analysis at Aalborg University in Denmark. "You just click on a button or type a few words, and then suddenly you burn so much energy."

Some smaller NFT platforms, including one known as Hic Et Nunc, have started using proof of stake, which doesn't require miners to compete to add assets to the blockchain. "It's just a more efficient algorithm," he said.