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01 September 2010

Can CO2 Be Stored Safely Underground

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Coal-fired power stations release more carbon dioxide per kWh than any other fossil fuel facility, and Germany has a large number of just this sort of power station.
It is estimated that around 40 billion tons of coal are stored in potential open cast deposits in Lusatia and the Lower Rhine Basin. That makes up 14 percent of world reserves. The question is, can the carbon dioxide emissions be captured and stored underground?

The idea of filtering carbon dioxide out of coal power station exhaust gases and storing it underground is certainly very attractive. A pilot power station - Schwarze Pumpe in Lusatia - has been burning coal in pure oxygen since 2008; and it is possible to segregate the resulting carbon dioxide emitted by this oxyfuel process.

Another power station in nearby Janschwalde will soon be commissioned. Other approaches to filtering emissions are showing promise around the world, and segregating greenhouse gases should not be a major problem in the future. However, such processes consume energy, thus reducing the overall efficiency of the power station.

Test storage facility in Brandenburg
Segregation is only the first step; for real Carbon Capture and Storage (CCS), the carbon dioxide must be pumped down 1000 metres into porous rock, and stay there. Such a facility is being tested in Ketzin, Brandenburg, sponsored by the EU and the German Federal Government. Forty thousand tons of carbon dioxide have already been pumped underground.

The project, called CO2SINK, is designed to test whether the gas will then remain underground reliably for decades or even centuries.

The safety of long-term underground storage of carbon dioxide is still an open question. Will such stores release their contents over time? Would this be hazardous for people and animals in the vicinity? This is a vanishingly small risk, but a loss rate of just one percent could sabotage all climate protection plans.


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