The 'cloud' of data that 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, Greenpeace said in a new report to be released today.

A Facebook facility being built in Oregon will rely on a utility whose main fuel is coal, while Apple is building a data warehouse in a North Carolina region that relies mostly on coal, the environmental organization said in the study.

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

The growing mass of business data, home movies and pictures has ballooned beyond the capabilities of many corporate data centers and personal computers, spurring the creation of massive server farms that make up a "cloud," an emerging phenomenon known as cloud computing.

The Greenpeace report comes during a global debate whether to create caps or other measures to cut use of carbon-heavy fuels like coal and curb climate change.

Cheap and plentiful, coal is the top fuel for US power plants, and its low cost versus alternative fuels makes it attractive, even in highly energy-efficient data centres.

Apple, Facebook, Microsoft Corp, Yahoo Inc and Google have at least some centres that rely heavily on coal power, said Greenpeace.

Most of the companies declined to give details of their data centers to Reuters. All said, however, they considered the environment in business decisions, and most said they were aggressively pursuing energy efficiency.

High technology companies say they support the environment. Apple has released its carbon footprint, or how much greenhouse gases it produces, and Facebook said it chose the location for its centre 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 centres.

Yahoo, which is building a center near Buffalo, New York, that Greenpeace saw as a model, will get energy from hydroelectric facilities. The company said energy-efficiency was the top goal, with a building design that promotes air circulation.

Data centre energy use already is huge, Greenpeace said.

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

The cloud may be the fastest-growing facet of technology infrastructure between now and 2020, said Greenpeace.