Amazon Web Services (AWS) has been singled out as among the "dirtiest" cloud providers in a Greenpeace report on the green credential of tech firms.
Google, Facebook and Apple were all praised by the non-governmental organisation, which said leading datacentre providers had taken key steps towards creating a greener internet since its last report on the subject in 2012.
If it were a country, the collective electricity demand of the cloud and internet would now rank in the top six thanks to massive growth in the online population, Greenpeace said.
That electricity demand will grow again by 60 per cent or more by 2020, it added.
Greenpeace lauded six major cloud brands – Apple, Box, Facebook, Google, Rackspace and Saleforce – for committing to a goal of powering datacentres with 100 per cent renewable energy.
Apple, which Greenpeace criticised in its 2012 How Green Is Your Cloud report, and Facebook were also pinpointed for making significant improvements in their energy transparency. However, transparency remains "weak" overall, particularly among colocation providers, the environmental group added.
AWS is among the "dirtiest and least transparent" companies in the sector, Greenpeace said. The world's largest public cloud provider was slammed for being "far behind its major competitors, with zero reporting of its energy or environmental footprint to any source or stakeholder".
AWS sources just 15 per cent of its electricity demand with clean energy, Greenpeace said, with coal powering 28 per cent of the firm's cloud, nuclear 27 per cent and gas 25 per cent.
"Apple is the most improved company since our last full report, and has shown itself to be the most innovative and most aggressive in pursuing its commitment to be 100 per cent renewably powered," it said.
In a statement quoted by the BBC, Amazon dismissed Greenpeace's findings.
"Greenpeace's report misses the mark by using false assumptions on AWS operations and inaccurate data on AWS energy consumption," it said.
"Running IT infrastructure on the AWS Cloud is inherently more energy efficient than traditional computing that depends on small, inefficient, and over-provisioned datacentres."
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