PURCHASE, New York: Within the space of a few months global warming has become a big issue for big business. And more so among marketers' object of desire - young consumers - where footroom on the environmental soap box is as desirable as Park Avenue real estate - and as costly.

"Companies are starting to say: 'I'm greener than you are,' " image consultant Katharine Paine told USA Today. But, mirror, mirror on the wall - who is the greenest of them all?

Crowned Monday by the Environmental Protection Agency as the greenest of the green was (deep breath now) PepsiCo, which confirmed its intention to purchase one billion kilowatt-hours of renewable energy credits over the next year.

That's equal to all the electricity used by all of PepsiCo's US facilities - and enough to power 90,000 average US homes for twelve months. Each credit represents a subsidy to help produce one megawatt hour of renewable electricity, such as wind power.

However, to put Pepsi's concern for the planet into perspective. the cost of its gesture is around $2 million - a gnat's bite from its annual US measured media spend (in 2005) of $1,466,770,000.

Nonetheless, says Bill Wehrum, the EPA's top federal air pollution official: "It's a big deal. They've vaulted to the top of the list."

Adds Rob Schasel, director of energy, utilities and conservation at PepsiCo: "To the extent we motivate other companies to get involved is a good thing for America — and for the planet."

Moreover, the move is hailed by environmental lobbyists. Blair Swezey, principal policy adviser at the National Renewable Energy Laboratory, says that deals like this "will create a new market pull for renewable energy."

Even such aggressive campaigners as Sierra Club are impressed. Lauds director of global warming Dave Hamilton: "This is extremely rare. It comes at a time when we're looking for a leader."

And after they've scrutinized the ROI, there's little doubt PepsiCo stockholders will like it too.

Data sourced from USA Today; additional content by WARC staff