A Heavy Load

To stave off global warming, some people have proposed sequestering huge amounts of carbon dioxide in the ocean or geological formations. But society could be paying the price for that strategy for thousands of years, a scientist argues in Nature Geoscience.

Gary Shaffer of the University of Copenhagen in Denmark ran the numbers on several different carbon dioxide storage scenarios. He predicted that deep-ocean sequestration would damage ecosystems, since the resulting changes to the water’s acidity and carbon dioxide levels could cause expansion of low-oxygen ‘dead zones’.

Storing carbon dioxide in geological formations could also backfire if the gas leaked too quickly, according to the study. At a ‘moderate’ leakage rate of 1 percent every 100 years, for example, the planet could eventually warm just as much as it would have under a ‘business-as-usual’ scenario in which carbon dioxide was not sequestered. Offshore sediments might perform better as storage sites, but it’s not clear how much carbon dioxide they can hold.

Future generations could respond to leaks by re-sequestering carbon dioxide, notes Shaffer. However, this task “would have to be carried out over many thousands of years,” he writes, “a burden for future society not unlike that of long-term management of nuclear waste.” – Roberta Kwok

Source: Shaffer, G. 2010. Long-term effectiveness and consequences of carbon dioxide sequestration. Nature Geoscience DOI: 10.1038/NGEO896.

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