SCHWARZE PUMPE, September 9, 2008 (AFP) - One of Europe's biggest power firms inaugurated a prototype coal-fired power station on Tuesday it says is almost emissions-free but environmentalists were unimpressed.

Located at the site of the massive 'Schwarze Pumpe' ('Black Pump') power station in eastern Germany, Sweden's Vattenfall said the new technology has the potential to allow coal to be burnt without releasing harmful greenhouse gases.

'Today industrial history is being written,' Vattenfall Europe's chief executive Tuomo Hatakka told a news conference. 'Coal has a future -- but not the carbon dioxide emissions from it.'

The new method being developed by Vattenfall is called Carbon Capture and Storage, or CCS, 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 carbon dioxide is compressed until it becomes liquid and then injected deep underground and safely sealed away, Vattenfall says.

In the case of the pilot plant near Spremberg close to the Polish border, the liquid carbon dioxide is taken 350 kilometres (210 miles) in lorries and injected 'for permanent storage' in a gas field in northern Germany.

But environment groups were far from happy.

Germany's BUND pressure group slammed CCS as a 'fig leaf' allowing new coal-fired power stations that chuck out millions of tonnes of carbon dioxide to be built while giving the appearance of addressing 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.

Greenpeace said that CCS decreases the amount of energy produced by coal-fired plants by 10 to 40 percent, meaning a much greater amount of coal must be burnt to produce the same amount of energy.

The effect will be higher prices for CCS electricity, critics cited by the left-leaning Tageszeitung said.

Opponents, who held a small demonstration Tuesday outside Schwarze Pumpe, say the technology would not be ready for the mass market before 2020.

But the World Wide Fund for Nature was more forgiving.

'CCS can serve as a technological bridge' until a better alternative is developed, WWF climate expert Regine Guenther told the Tageszeitung.

She called for more research in the field, funded by the energy sector.

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 are destinations for the emissions from Schwarze Pumpe's pilot plant.

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 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 postcombustion, whereby CO2 is 'washed' from the flue gas after conventional combustion, and precombustion 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.