The world’s most popular cryptocurrency promised to revolutionize the world. While its success is still inconclusive, its price is very clear: Bitcoin has become a significant contributor to global emissions.

The idea behind cryptocurrencies is nothing short of innovative. They offer anonymity, no sales tax and freedom from bank and government interference. It’s a decentralized system. It doesn’t require any banks or central authority: transactions are stored digitally as “blocks” in a chain that is kept by a network of peers. It’s a true “power to the people” approach and relying on a set of impressive technological advancements.

But while Bitcoin, by far the most used cryptocurrency, has been used successfully in some projects, it’s still failed to bring the revolution it promised — and at the same time, it’s ushered in an unexpectedly high environmental cost.

Bitcoins are “mined” by solving complex puzzles, which require substantial computational power. Essentially, the Bitcoin miners try to find a random value (called a nonce value), and every time they do so, an algorithm is applied to map the data. This process is extremely computationally-intensive; if you want to mine Bitcoins, you need several powerful processors, and these processors use up a large amount of electricity. This electricity is the main environmental cost of cryptocurrencies — a cost which also translates into an economic and health cost.

For the most part, people are mining bitcoins to make money. To do this, you need to ensure that the price of the electricity you are using is lower than the price of the bitcoins you are producing. This means that most of the bitcoin mining takes place in places where electricity is cheap. Large facilities tend to be more efficient, but especially in warmer climates, they may require additional energy for cooling and other inefficiencies.

The problem is that in most places that have cheap electricity, this electricity is still coming from fossil fuels. Iceland is a notable exception, as its electricity comes almost exclusively from geothermal sources — but despite Iceland raising massive interest from Bitcoin miners, Iceland still accounts for only around 4% of the globally mined Bitcoin. Other parts of the world, like Inner Mongolia or Xinjiang in northwestern China produce over 10% of the global Bitcoin, with Russia and Alberta also being Bitcoin hotspots. What do all these areas have in common? Cheap, dirty, fossil fuels.

In a new study, Susanne Köhlerand Massimo Pizzol from Aalborg University in Denmark analyzed the global emissions associated with the production of Bitcoin.

Overall, while the total estimate for Bitcoin greenhouse gas emissions came up lower than previous estimates, it is still on par with that of a small country. Bitcoin is responsible for 17.29 megatons of CO2. For comparison, Ghana — a country of almost 30 million people — emits just a bit over Bitcoin, at 18.2 megatons. Croatia and Lithuania are both in the same range of emissions.

Not all areas emitted the same. The dirtier the energy mix was, the more emissions were generated. Coal, in particular, produces the most emissions, and this was visible in the larger emission share of areas that derive much of their energy from coal.

Since places like Iceland, Sweden, or Norway (countries in which around 4% of the world’s Bitcoin is mined) have much cleaner electricity, researchers suggest that moving mining facilities to these areas would reduce the environmental impact on Bitcoin.

Regulating cryptocurrency mining, for instance adding a tax to compensate for its environmental impact, would be extremely difficult, researchers write. This is only a technical analysis — policy or regulation measures could help reduce this environmental impact, but the deregulated nature of Bitcoin is exactly what makes it so appealing. Additionally, the technical intricacies of regulating cryptocurrencies are also difficult to overcome.

“This analysis of the Bitcoin mining network contributes with a strictly technical perspective to the broader discussion on the sustainability of the international cryptocurrency. The results should be considered in the larger context of a borderless currency that is difficult to regulate and where political and economic concerns play as important a role as technical and environmental ones. Bitcoin is not only difficult to regulate because it is a global currency, but also because of its governance structure,” the study concludes.

The study has been published in Environmental Science and Technology.