A single Bitcoin transaction carried an average water footprint of about 16,000 litres in 2021 once the electricity and cooling behind it were counted — roughly 6.2 million times the water behind one credit-card swipe, and the figure rises and falls with the price o

In 2021, the average transaction recorded on the Bitcoin blockchain carried an estimated water footprint of roughly 16,000 litres, once the water used to generate the electricity behind the mining process and to cool the machines doing the work is added up. That figure, drawn from a peer-reviewed study published in the Cell Press journal Cell Reports Sustainability, works out to roughly 6.2 million times the water footprint of a single credit-card swipe, based on de Vries’ own estimate — discussed in a later interview with Greenpeace rather than the paper itself — that one card transaction carries a footprint of around 2.6 millilitres.

The research, titled “Bitcoin’s growing water footprint,” was published online in late November 2023 by Alex de Vries, a data scientist with a background in financial economics who tracks the industry’s resource use. De Vries built his estimate around two components. The larger of the two, accounting for roughly 80 to 90 percent of the total, is indirect water use: the water consumed at power plants to generate the electricity that miners buy, whether through evaporative cooling at thermoelectric plants, hydropower reservoir evaporation, or other generation methods. The paper calculates this by combining data on where Bitcoin’s computing power is located with regional water-intensity figures, expressed in litres of water per kilowatt-hour of electricity produced on that grid.