Bitcoin : electricity consumption comparable to that of Poland

In 2024, the price of bit­coin soa­red, rea­ching its highest levels since its crea­tion. Bit­coin is the most wide­ly used cryp­to­cur­ren­cy. Its mar­ket capi­ta­li­sa­tion rea­ched over $1.3 tril­lion on Octo­ber 21, 2024, com­pa­red with Ethereum’s $321 bil­lion just behind. One bit­coin is worth over $67,000 (as of Octo­ber 21, 2024). This surge has an envi­ron­men­tal cost, which is also rising shar­ply. “Bit­coin is based on blo­ck­chain tech­no­lo­gy : by defi­ni­tion, com­pu­ters per­form iden­ti­cal cal­cu­la­tions (around 15,000 times) to ensure the network’s secu­ri­ty,” explains Jean-Paul Dela­haye. “The pro­to­col used for bit­coin has a very high ener­gy cost ; it’s an envi­ron­men­tal waste.”

The annual elec­tri­ci­ty consump­tion dedi­ca­ted to bit­coin mining [Editor’s note : the pro­cess by which bit­coins are issued and gene­ra­ted] is com­pa­rable to that of Poland. It is esti­ma­ted at 155 TWh per year to 172 TWh per year (or 162 TWh per year accor­ding to the Cam­bridge Centre for Alter­na­tive Finance). The Inter­na­tio­nal Ener­gy Agen­cy (IEA), meanw­hile, esti­mates that cryp­to­cur­ren­cies would have consu­med 110 TWh of elec­tri­ci­ty by 2022, or 0.4% of annual glo­bal demand¹.

As a result, bitcoin’s car­bon foot­print is signi­fi­cant, and some scien­tists are war­ning of the urgent need for action². In 2021, bitcoin’s envi­ron­men­tal foot­print sud­den­ly increa­sed. While the majo­ri­ty of miners were based in Chi­na (73%), the coun­try deci­ded to ban bit­coin mining on its ter­ri­to­ry³. Most of the acti­vi­ty is now relo­ca­ted to Kaza­khs­tan and the Uni­ted States. The car­bon foot­print of bit­coin mining is direct­ly lin­ked to the green­house gases relea­sed during the pro­duc­tion of the elec­tri­ci­ty that powers the com­pu­ters per­for­ming the cal­cu­la­tions. The more car­bon-inten­sive the country’s elec­tri­ci­ty mix, the higher bitcoin’s car­bon foot­print. The share of rene­wable ener­gies powe­ring bit­coin mining has fal­len from 41.6% to 25.1% fol­lo­wing the mas­sive relo­ca­tion in 2021. In 2022, the Cam­bridge Cen­ter for Alter­na­tive Finance esti­mates the share of rene­wables at 37.6% inclu­ding nuclear power and 26.3% exclu­ding nuclear power ⁴. As a result, CO₂ emis­sions from bit­coin mining are esti­ma­ted at 77, 85 or even 96 mil­lion tonnes of CO₂ per year, depen­ding on the source. By com­pa­ri­son, France’s equi­va­lent CO₂ emis­sions (all green­house gases com­bi­ned) will amount to 385 mil­lion tonnes in 2023.

But the envi­ron­men­tal impact of bit­coin mining is not limi­ted to green­house gas emis­sions. In 2024, an article publi­shed in the jour­nal Cell Reports sus­tai­na­bi­li­ty⁵ esti­mates the water foot­print of the cryp­to­cur­ren­cy. The author esti­mates that it will amount to 1.5 bil­lion litres of water in 2021. The culprit ? The use of water for the cooling sys­tems of the ser­vers used for mining, and indi­rect use to pro­duce elec­tri­ci­ty via the cooling of ther­moe­lec­tric power sta­tions. Other authors arrive at dif­ferent esti­mates based on the envi­ron­men­tal foot­print of elec­tri­ci­ty pro­duc­tion in the coun­tries hos­ting bit­coin miners. Their esti­mates are much higher, due to the inclu­sion of eva­po­ra­tion from hydroe­lec­tric dams. They esti­mate bitcoin’s water foot­print at 1,650 bil­lion litres bet­ween Janua­ry 2020 and Decem­ber 2021 (the equi­va­lent of 660,000 Olym­pic swim­ming pools), or around 800 bil­lion litres per year. “I find the deci­sion to include eva­po­ra­tion from hydroe­lec­tric dams in the water foot­print of bit­coin mining a deli­cate one,” says Jean-Paul Dela­haye. “It’s dif­fi­cult to dis­tin­guish bet­ween water used for bit­coin and other uses.” As for the land foot­print, for the same per­iod it was esti­ma­ted at 1,870 km².

It is dif­fi­cult to accu­ra­te­ly cal­cu­late the envi­ron­men­tal impact of bit­coin mining. There is no regis­ter of the machines used for mining and their exact ener­gy consump­tion. “Howe­ver, we do have a mini­mum esti­mate, which is enough to show that ener­gy consump­tion is exces­sive,” asserts Jean-Paul Dela­haye. The esti­mates are based on the “hash” com­pu­ting power of the net­work – known to within a few percent – and on the mini­mum consump­tion by the best machines to pro­duce 1 hash, which is an opti­mis­tic view of the hard­ware in use. “There are two main metho­do­lo­gies that have been deve­lo­ped in recent years to assess the ener­gy consump­tion of the bit­coin net­work, one based on eco­no­mic simu­la­tions and the other on tech­no­lo­gies,” explains Chris­tian Stoll. “But they pro­duce simi­lar results”. And with the rise in the price of bit­coin, the fore­casts are fair­ly pes­si­mis­tic : even if the rela­tion­ship is not uni­form, the higher the price of bit­coin – remem­ber that it will reach record levels in 2024 – the higher the ener­gy consump­tion will be⁶.

Bitcoin’s high ener­gy consump­tion is lin­ked to the way it works, as Jean-Paul Dela­haye explai­ned in a pre­vious article : “The issue and cir­cu­la­tion of bit­coin is mana­ged by a net­work of com­pu­ters that ope­rates in a decen­tra­li­sed man­ner. Each com­pu­ter on the net­work holds a copy of the “blo­ck­chain”, a file sum­ma­ri­sing all the infor­ma­tion on the content of all the bit­coin accounts and all the tran­sac­tions car­ried out on the net­work. To encou­rage new com­pu­ters to take part in mana­ging the bit­coin net­work, a reward is dis­tri­bu­ted eve­ry 10 minutes to one of them in a com­pe­ti­tion cal­led proof of work. We know this pro­cess as “mining”, and it is pre­ci­se­ly this pro­cess that involves a signi­fi­cant expen­di­ture of elec­tri­ci­ty.” In 2021, around 2.9 mil­lion com­pu­ting devices were dedi­ca­ted to bit­coin mining. “Over the past 2 years, Ethe­reum has swit­ched from a proof-of-work pro­to­col to a proof-of-stake pro­to­col : this has redu­ced the network’s ener­gy consump­tion by at least a fac­tor of 100,” points out Jean-Paul Dela­haye. By impro­ving trans­pa­ren­cy and regu­la­tion, deve­lo­ping alter­na­tive ener­gy-saving cryp­to­cur­ren­cies and adop­ting gree­ner blo­ck­chain vali­da­tion pro­to­cols, the scien­tists are cal­ling for seve­ral levers to be acti­va­ted to reduce bitcoin’s envi­ron­men­tal footprint.

Anaïs Marechal