Is the bubble bursting in terms of negative press for carbon dioxide (CO2)? With the PepsiCo's use of CO2 for its newest vending machines, the gas appears to be in favour as a more environmentally-friendly option.

Pepsi's new vending machines use CO2 to lower their impact on the environment, thought to use 15% less energy and emitting 12% fewer greenhouse gas emissions than typical vending machines.

The new machines, which use CO2 as a refrigerant instead of hydrofluorocarbons (HFCs), are being rolled-out in a pilot programme which includes 30 machines in the Washington, D.C., area in the US.

HFCs were first used as refrigerants to replace chemicals that depleted the ozone layer, but are also thought to be thousands of times more potent than CO2 in terms of global warming potential - causing some groups and companies, mostly in Europe and Asia, to switch to CO2 or hydrocarbons.

Pepsi is believed to have already improved the performance of its vending machines, with its 2008 models using 51% less energy than 2003 models. The company is reported to have indicated it is also testing machines that use hydrocarbons isobutane and propane as refrigerants, elsewhere in the world.

Fellow beverage giant and rival company Coca-Cola has been using alternatives to HFCs in vending machines for years, starting with the 2004 Summer Olympics in Athens.

The company is believed to have issued around 8,000 HFC-free vending machines at events like the Torino 2006 Winter Olympics, the 2006 FIFA World Cup, the 2007 World Economic Forum in Davos, and the 2008 Summer Olympics in Beijing.

For the 2010 Olympic Winter Games in Vancouver, Coca-Cola's 1,400 coolers and vending machines won't use HFCs and the company hopes to have up to 100,000 HFC-free vending machines and refrigerators around the world by 2010.

According to the news report by Greenbiz.com, Pepsi currently has 4-5 million vending machines worldwide, while Coca-Cola also has around 10 million vending machines and coolers in operation across the globe.