A Tuesday Greenpeace report that studied the environmental impact of the cloud criticized firms like Apple, Microsoft, Twitter, and Amazon for lagging behind their Web counterparts. The firms, however, took issue with that characterization. Amazon, Apple, and Microsoft "are all rapidly expanding without adequate regard to source of electricity, and rely heavily on dirty energy to power their clouds," Greenpeace said in its report, dubbed "How Clean Is Your Cloud?" Facebook, which has tangled with Greenpeace in the past, earned high praise from the group for committing to renewable energy, particular with its new data center in Sweden. Greenpeace also lauded Google and Yahoo for "prioritizing access to renewable energy in their cloud expansion, and [becoming] more active in supporting policies to drive greater renewable energy investment."