The 'cloud' of data which is becoming the heart of the Internet is creating an all too real cloud of pollution as Facebook, Apple and others build data centers powered by coal, according to a new Greenpeace report.

A Facebook facility will rely on a utility whose main fuel is coal, while Apple Inc, expecting its Web-browser iPad launch on April 3, is building a data warehouse in a North Carolina region powered by coal, the environmental organization said in the study to be released on Tuesday.

The last thing we need is for more cloud infrastructure to be built in places where it increases demand for dirty coal-fired power, concluded Greenpeace, which argues that Web companies should be more careful about where they build and should lobby more in Washington, DC for clean energy.

The growing pile of home movies, pictures and business data has ballooned beyond the capabilities of personal computers and even average corporate data centers, spurring the creation of massive server farms with tens of thousands of specialized machines that make up the cloud.

The report comes in the middle of a new federal debate whether to create caps or other measures to cut use of carbon-heavy fuels like coal and curb climate change.

Apple, Facebook, Microsoft Corp, Yahoo Inc and Google Inc all have at least some centers with heavy use of coal power, said Greenpeace. The companies declined to give details of their data centers, but all said they considered the environment in business decisions, and most said they were aggressively pursuing efficiency.

Cheap and plentiful, coal is the top fuel for U.S. power plants, and its low cost versus alternative fuels makes it attractive, even in highly efficient data centers.

Technology companies say they support the environment. Apple releases its carbon footprint, or how much greenhouse gases it produces, and Facebook said it chose the location for its center in order to use natural means to cool its machines.

Microsoft said it aimed to maximize efficiency, and Google said it purchased carbon offsets -- funding for projects which suck up carbon -- for emissions, including at data centers.

Yahoo, which is building a center near Buffalo, New York that Greenpeace saw as a model, will get energy from hydroelectric facilities, but the company said efficiency was the top goal, with a long narrow and tall building that looks like a chicken coop and promotes air circulation.

Data center energy use already is huge, Greenpeace said.

If considered as a country, global telecommunications and data centers behind the cloud would have ranked fifth in the world for energy use in 2007, behind the United States, China, Russia and Japan, it concluded.

And the cloud may be the fastest growing portion of technology growth between now and 2020, said Greenpeace.

The group based its findings on a mix of data including a federal review of fuels in U.S. zip codes in 2005 and a 2008 study by the Climate Group and the Global e-Sustainability Initiative, which Greenpeace updated in part with U.S. Environmental Protection Agency data.

(for more environmental news see our Environment blog at http://blogs.reuters.com/environment)

(Reporting by Peter Henderson)