Beneath the waves: the future of carbon capture and storage

The need to capture and store carbon pumped out by power stations has prompted deep-sea research by US scientists
David Adam
guardian.co.uk, Wednesday 11 November 2009 20.05 GMT
If you could capture the carbon that thousands of power stations would otherwise pump into the atmosphere, where would you put it?
According to the International Energy Agency, the world needs to fit 3,400 coal-fired power stations with technology to capture carbon dioxide by 2050.
So-called carbon capture and storage (CCS) is often labelled as expensive and unproven, though most of the problems are with the capture part of the process. Energy-hungry scrubbers are needed to soak the greenhouse gas from the exhaust gases, which drain the clean coal's power output and reduce its efficiency.
When it comes to storing the billions of tonnes of carbon dioxide that would be captured, the answer for Britain seems obvious – we can put it under the North Sea, in our emptying natural gas fields. But where do nations without access to such convenient geology turn? One option is to pipe waste gas directly into the sea. In very deep water, scientists think carbon dioxide would form a dense slush that would stay on the seabed for hundreds of years. Wally Broecker, a climate expert at the Lamont-Doherty Earth Observatory at New York's Columbia University, says 480bn tonnes of carbon dioxide could be safely dumped in the deep Pacific in this way: the amount created by about 16 years of the world's current fossil fuel use.
Scientists in the US have tested this concept, and the impact it could have on deep-sea life. Experts at the Woods Hole Oceanographic Institution and the Monterey Bay Aquarium Research Institute released small amounts of liquid carbon dioxide into a series of plastic cylinders on the seabed, some 3,000m down in waters off California. A few weeks later, samples of marine life were taken from inside the experiments, the surrounding sea bed and from some 100m away.
The scientists were interested in the reaction of three types of tiny sea creatures called foraminifera – single-celled organisms that make up a large part of life at the bottom of the deepest oceans and are a critical link in marine food webs.
The study found the survival of the tiny creatures depended on whether they formed shells, called tests. Those that did not make shells, or used particles they scavenged from the surrounding seabed, were not affected. Less fortunate were the foraminifera that build calcium carbonate shells: they were wiped out where they came into direct contact with the carbon dioxide. Writing in the journal Global Change Biology, the scientists say these calcareous foraminifera will face "considerable challenges" in areas where CO2 is dumped.