Nature's cure

Environ. Sci. Technol. doi:10.1021/es0701816 (2007)

Credit: Getty

Scientists have proposed a novel approach to removing carbon dioxide from the atmosphere based on the Earth's natural weathering process. Not only could the technology mitigate global warming, it could also counteract continued acidification of the ocean, which threatens marine life.

The technology, invented by Kurt Zen House, a PhD candidate at Harvard's Department of Earth and Planetary Sciences, and co-workers, involves electrochemically removing hydrochloric acid from the ocean, neutralizing it by reaction with silicate rocks and returning it to the sea. By increasing ocean alkalinity, the process would enhance the absorption of atmospheric CO₂. Over time, the CO₂ would mix throughout the ocean and eventually precipitate as calcium carbonate in ocean sediments. This method of carbon capture and storage could effectively transfer CO₂ from the atmosphere to the ocean for hundreds of years or longer. And unlike natural chemical weathering, in which weak carbonic acid slowly dissolves silicate rock, this process uses concentrated hydrochloric acid to dissolve silicate, thus accelerating the pace to industrial rates.

But the scientists acknowledge that offsetting even around 15% of global greenhouse-gas emissions would be a considerable task. They say that implementation of the technology would be ambitious and costly, and could have unknown environmental risks of its own.