BERLIN: One of Europe's biggest power companies inaugurates on Tuesday a pilot project using a technology that it is presenting as a huge potential breakthrough in the fight against climate change.

But green campaigners have denounced the project as a cosmetic operation that does not really address the problem of global warming.

At the site of the massive "Schwarze Pumpe" ("Black Pump") power station in the old East Germany, Vattenfall wants to the new method to allow it continue burning coal -- but with radically reduced emissions.

To do so, the Swedish firm is using Carbon Capture and Storage, or CCS for short, which captures the greenhouse gases produced when fossil fuels are combusted.

This prevents the greenhouse gases escaping into the Earth's atmosphere and contributing to global warming.

The captured gases are then sharply compressed until they become liquid and are injected deep underground, sealed away and therefore will not contribute to the increase in the Earth's temperature, Vattenfall says.

In the case of the pilot plant at Spremberg near the Polish border, the concentrated carbon dioxide is injected "for permanent storage" in a gas field in northern Germany.

Underground reservoirs of carbon dioxide already occur naturally in geological formations where it has been trapped by sedimentary rocks in much the same way as oil or gas, it says.

Depleted gas and oil fields -- such as the destination for Spremberg's emissions -- are one possibility for storage, as are fields still with some oil and gas still in them.

Another option are geological formations currently filled with salty water, which can partially absorb the CO2 and in some cases react with minerals to form carbonates, permanently trapping the CO2, Vattenfall says.

The plant in eastern Germany between Dresden and Berlin is also the first in the world to use a new way of burning the coal -- in this case lignite, to be precise -- known as oxyfuel combustion.

This involves burning the coal in pure oxygen so that practically the only so-called flue gas produced is carbon dioxide as opposed to the cocktail of different gases emitted by conventional technology, making CCS easier.

The other two methods are known as post-combustion, whereby CO2 is "washed" from the flue gas after conventional combustion, and pre-combustion in which a gasification process removes carbon from the fuel before being burnt.

With around two-thirds of the world's power generated by burning fossil fuels and humanity set to rely heavily on these "for the foreseeable future," Vattenfall says the new technology is the way forward.

"CCS will work as a temporary solution that buys us the time we need to develop a sustainable energy system in the future. We say that CCS is a way of 'bridging to the future'," according to Vattenfall's website.

"This represents an important milestone in our efforts to radically reduce our own carbon dioxide emissions and develop technology to reduce emissions on a global basis."

The firm has invited around 400 guests to participate in Tuesday's grand inauguration, including representatives from both the Swedish and German governments.

But environment groups are far from happy.

Germany's BUND pressure group for instance slammed CCS as a mere "fig leaf" allowing companies and governments to continue building new coal-fired power stations while giving the appearance of caring about global warming.

"Vattenfall managers talk a lot about supposedly environmentally friendly coal power stations but they are still planning and building conventional coal-fired power stations with high levels of CO2 emissions," BUND's energy spokesman Thorben Becker said.