In the ongoing battle against global warming, researchers on Tuesday began drilling an underground geological reservoir for carbon dioxide in the small town of Ketzin, west of the German capital. Over the next two years, scientists will be examining if and how harmful CO2 gases can be pumped deep under the earth.

"The storage of this greenhouse gas can be an option for winning time in developing and introducing CO2-free energy technologies," said Rolf Emmermann, head of Germany's National Research Center for Geosciences GFZ in Potsdam. The GFZ is spearheading the so-called "CO2SINK" project.

However, Emmermann said it was vital to examine which processes the underground storage could trigger and what will occur with the stored CO2 in the medium and long-term.

Carbon dioxide accumulation is believed to be the main cause of global warming. The gas is produced for example by burning fossil fuels such as coal, gas and oil.

Researchers to look at long-term risks

Scientists at the Ketzin facility will be pumping 60,000 tons of carbon dioxide some 700 meters into an underground reservoir that is covered by a layer of virtually impermeable clay and cement, which act as a cover and keep the gas below the earth's surface.

It is the first time in Europe that scientists are studying how CO2 can be injected under high pressure into so-called saline aquifers. These are underground layers of water-bearing porous rock.

According to Emmermann, the amount of gas stored in the formation corresponds to the amount of carbon dioxide Potsdam's population exhales annually.

"These marginal amounts, compared to the entire CO2 output in Germany, will suffice to gain significant insight into injection technology, the reservoir's security and possible long-term risks," he said.

The scientists are employing a gas with 99.9 percent purity, which is normally used in beverages such as mineral water and beer.

Critics question project's implications

The environmental protection group BUND called the project "a red herring." According to BUND's climate protection expert Matthias Seiche, 26 coal-burning power plants, which run on conventional technology, will be built in Germany in the next few years.

Seiche said projects like CO2SINK gave the impression that there were "clean" facilities.

"The enormous investments being made in storage should be put into renewable energies," Seiche said.

Greenpeace's Gabriela von Goerne said she feared the experiment could cause the ground to become stale or unstable.

"The saltwater in the sandstone could be displaced by the carbon dioxide," von Goerne said.

The CO2SINK project worth 35 million euros ($46 million) is supported by the European Commission, the German government and private companies from eight European nations. Eighteen partners from nine countries are also involved.