Convenient CO2 storage sites identified

British researchers have identified ocean floor regions suitable for storage of large volumes of CO2.

The University of Southampton team, led by PhD student Chiara Marieni, has investigated the properties of CO2 and created global maps of the ocean floor to determine where the greenhouse gas could be safely stored.

"We have found regions that have the potential to store decades to hundreds of years of industrial carbon dioxide emissions although the largest regions are far off shore,” Marieni said. “However, further work is needed in these regions to accurately measure local sediment conditions and sample the basalt beneath before this potential can be confirmed."

Among the five suitable regions are sites off the cost of Australia, Japan, Siberia, South Africa and Bermuda, ranging in size from ½ million square kilometres to almost four million square kilometres.

At high pressures and low temperatures, such as those in the deep oceans, CO2 occurs in a liquid form that is denser than seawater. By estimating temperatures in the upper ocean crust, the team was able to identify where it may be possible to store large volumes of CO2 in the basalts in the stable liquid stable form.

Basalts are fractured rocks with high proportions of open space and over time may also react with the CO2 locking it into solid calcium carbonate, permanently preventing its release into the oceans or atmosphere.

As a precaution, only those locations have been selected were a thick blanket of impermeable sediments prevents the gas from escaping.

Burning of fossil fuels such as coal, oil, and natural gas has dramatically increased concentrations of CO2 in the atmosphere and triggered the climate change and ocean acidification.

Although technologies are being developed to capture CO2 at major sources such as power stations, this will only avoid further warming if that CO2 is then safely locked away from the atmosphere for centuries.

The study, published in Geophysical Research Letters, shows that previous studies, which concentrated on the effect of pressure to liquefy the CO2 but ignored temperature, have pointed to wrong locations, where high temperatures mean that the CO2 will have a low density, and thus be more likely to escape.

Funding for this research was provided by the University of Southampton Vice-Chancellor's Scholarship and the Natural Environment Research Council (NERC).

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