How to handle carbon dioxide? Lock it in rock

Trapped in basalt
If proven effective, McGrail said, most of the cost associated with such a storage strategy would be tied up in the initial capture and transport of the carbon dioxide. With the necessary right-of-ways and construction premiums, for example, pipelines can command $1 million or more per mile, a big reason why he and other proponents say configuring future power plants near the underground storage sites would make the most fiscal sense.

Carbon dioxide could be injected into a single well at a rate of more than a few hundred kilotons per year, permitting the sequestering of emissions from a small to mid-sized coal-fueled power plant. McGrail said other regions of the country with sizeable basalt formations and a dearth of storage alternatives, notably the Southeast, would stand to benefit by adopting similar strategies. Already, a $2.2 billion coal-fired plant that would bury about two-thirds of its own carbon dioxide has been proposed for a location near the Washington test site, pending the pilot project’s success.

Michael Aziz, a professor of materials science at Harvard University, said he was intrigued by the basalt-trapping approach’s capacity for storing vast amounts of carbon dioxide, though he worried about the possibility of CO₂ leaking back into the atmosphere. “I hope it works,” he said.

Nature-driven approach
Aziz and colleagues at Harvard and Pennsylvania State University have staked out a nature-driven approach to storing the gas in an even bigger reservoir: the ocean. Normally, carbon dioxide dissolves in rain and other freshwater to form weak carbonic acid. When the solution percolates through rocks, the acid converts to an alkaline solution that flows into the ocean, increasing its ability to retain dissolved carbon.

“The idea is to mimic the way nature takes CO₂ out of the atmosphere by building a series of chemical and electrochemical reactions,” Aziz said. “When you put them together and put a box around them, the output is identical to the chemical weathering of the Earth.” Easier said than done, of course, but the team published a recent study concluding that substituting nature’s weak carbonic acid with more potent hydrochloric acid could dramatically speed up the process.

Under the most optimistic scenario, Aziz said, the solution might be capable of offsetting 10 percent to 20 percent of projected increases in carbon dioxide levels. But he warned that such strategies shouldn’t be used as a justification to relax efforts aimed at reducing emissions. McGrail agreed, arguing that in order to affect carbon dioxide levels, people will need to completely transform how they use resources on a global scale. “It’s not an excuse to cut back on conservation programs or energy renewal programs,” he said.

Nevertheless, McGrail said the deep basalt sequestering strategy may have the least economic impact in terms of stabilizing atmospheric emissions, especially for developing countries like India and China. India’s National Geophysical Research Institute, in particular, has expressed a keen interest in the results of the pilot study. With India’s carbon dioxide emissions expected to escalate rapidly in the coming years, scientists have begun exploring a similar storage solution within the country’s mammoth Deccan Trap, a natural basalt formation about 10 times bigger than its Pacific Northwest counterpart.

Noting that research has linked the formation of vast volcanic flows with mass extinctions in the distant past, McGrail and his co-authors concluded in a study published last year, “it would indeed be ironic if these same geologic formations become an important part of the solution to the present-day greenhouse gas management challenge.”

Ironic, perhaps, but also inspired.

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