Apple is one of several global tech firms given poor marks for its heavy use of coal in powering datacenters in the Greenpeace report.

Despite its denial of the Greenpeace claim, Apple announced in May that it will power its North Carolina datacenter entirely by renewable energy sources by end-2012. This took place after Greenpeace infiltrated Apple's Cupertino campus and projected messages from Twitter and Facebook users who are dismayed at Apple's use of coal at the datacenter that powers its iCloud sources.

Apple CFO Peter Oppenheimer said that Apple's plans have been in place since last year, and declined to comment on whether the changes were made following Greenpeace's protests.

According to Apple, its North Carolina datacenter will have 60% of its power produced onsite from renewable sources while the other 40% will be purchased from local and regional renewable sources. In addition, Apple is building the largest non-utility fuel cell installation in the US, and the nation's largest private solar arrays, in order to provide renewable energy, the company added.