

At the dawn of cryptocurrency, mining seemed like a novel and useful way to distribute digital money. You could churn away with a laptop CPU and earn Bitcoin while supporting the blockchain that verified transactions. Today, Bitcoin requires a lot more power to crunch the numbers, and the proliferation of other cryptocurrencies means even more energy spent on mining digital coins. How much energy? An analysis published in the journal Nature Sustainability says you’d generate more wealth expending that energy on real mining. Like, the digging in the ground kind of mining.

Bitcoin is still the most widely used cryptocurrency, so it’s naturally the most valuable. Early this year, the value peaked around $20,000. That was just a momentary spike. In the space of a few weeks, Bitcoin lost about two-thirds of its value, taking other coins down with it. As of this writing, a Bitcoin is worth around $6,400. The separate Etherium currency is worth about $200.

The wild fluctuations in price are certainly part of the problem—it takes the same amount of energy to produce a Bitcoin if it’s worth $6,000 or $20,000. Apparently, it may not be worth the energy to mine crypto unless it becomes much more valuable and stays that way. Study authors Max Krause and Thabet Tolaymat found that it takes more energy to make $1 worth of Bitcoin or Monero than it does to dig $1 worth of gold or copper out of the ground.

There is some variation among currencies, though. To mine the equivalent of $1, the study found Bitcoin requires 17 megajoules of power, and Monero isn’t far behind with 14 megajoules. Both Etherium and Litecoin are a bit more economical at about 7 megajoules. If you want to mine $1 of gold, that’s just 5 megajoules. Copper? 4 megajoules. Rare earth metals only consume 9 megajoules per $1. The exception is aluminum, which requires 122 megajoules per $1 of value.  

Bitcoin miners use multiple racks of ASIC mining rigs like this.

This is not just an analysis of cryptocurrency value and efficiency right now. The pair looked at the last two and a half years of Bitcoin, Ethereum, Litecoin, and Monero to arrive at these values. During that time, mining those four currencies generated between 3 million and 15 million tons of carbon dioxide. That’s a wide range because it’s hard to know exactly where all the energy use is happening. In China, where most Bitcoin mining takes place, power comes almost entirely from fossil fuels that produce more carbon.

Cryptocurrency is already a questionable use of energy based on the realities of mining, but the analysis from Krause and Tolaymat doesn’t even take into account all the things that go along with mining. For example, large mining operations need industrial cooling systems to keep all the machines running. Some crypto enthusiasts count on mining to become more efficient over time, but efficient hardware is also more expensive. With the value of crypto so unpredictable, operations might be wary of spending more without a guaranteed return.

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