Data centre growth leads to massive water and energy demands creating an environmental crisis

Image of data centre by Rsparks 3. Reproduced under creative common licence.

From an environmental perspective there is not a lot of good things to say about data centres and their rapid growth. Globally they are using about 2% of global electricity which is estimated to rise to as much as 5% by the end of the decade.  Of course the gigawatts of electricity being consumed represents gigatonnes of CO2 emissions. The lesser known fact is that they are consuming about 5 billion m³ of water every year for cooling.

A lot of suggestions have been made as to how this waste heat could be used in particular district heating and heat to electricity conversion. However, according to Diaz-Martin and Berquist (2025) two new innovative ideas are showing huge promise in terms of economic value and contributing to net zero.  These are direct air capture (DAC) of carbon dioxide which in theory could remove up to 1,000 megatonnes of CO₂ annually contributing to decarbonization goals; or thermal water purification to desalinate water, although current waste temperature of typically 30—70^oC is rather low on its own.

Currently much of this cooling water is finding its way to surface waters.  No only can it result in thermal pollution of lakes and rivers, but as up to 70-80% of the cooling water can be lost by evaporation it becomes mildly saline, causing salinisation.  Reclaimed water is often used with other installations employing recirculation, however the water eventually becomes too saline and needs to by released for treatment or disposal.  Some installations have been forced to treat this water on site using nanofiltration or reverse osmosis. However, this may not be all what it seems as data centres require high purity water for cooling as any particles can become lodged within the cooling system itself reducing efficiency, while corrosion and biofilm development in particular, which reduces heat transfer, are also problematic. So treatment is often primarily to protect the cooling system with concentrated reject process water then having to be discharged to sewer or surface water.

In Ireland it is estimated that data centres have consumed over 1.7 million m3 of water over the past two years. But Uisce Éireann has responded that data centres are only using 0.3% of current supply and are not seen as a problem citing modern cooling techniques reducing demand, while other centres have taken advantage of their own groundwater supplies or supplemented supplies by using rain water harvesting and on-site storage.  Oxford University (2026) has also looked at this problem suggesting that perhaps companies are not pricing water correctly when situated in water risk areas. Microsoft (2020) has been experimenting with underwater data centres off the coast of Scotland, by placing watertight units on the cold sea bed which reduced energy consumption significantly and required no water for cooling.

Diaz-Marin, C., D. and Berquist, Z. J. (2025) Flipping the switch: carbon-negative and water-positive data centres through waste heat utilization. Energy and  Environmental Science, 18, 8403-8413.  https://doi.org/10.1039/d5ee02676h

Microsoft (2020) Microsoft fiunds underwater databases are reliable, practical and use energy sustainably. https://news.microsoft.com/source/features/sustainability/project-natick-underwater-datacenter/

Oxford University (2026) Water guzzling data centres, Oxford e-Research Centre, Department of Engineering Science. University of Oxford.  https://eng.ox.ac.uk/case-studies/the-true-cost-of-water-guzzling-data-centres