CO2 Sequestration Likely To Acidify Groundwater, Release Metals - ES&T

[hatrack]

Injecting CO2 deep within the earth remains one of the more promising methods of getting rid of the greenhouse gas. So far, rocks, composed of porous sandstone filled with salty water many hundreds of meters below the surface, are the main storage-site candidates. Multiyear projects in such settings, from the North Sea to Canada, are generating encouraging results.

But preliminary geochemical data from the first U.S. project to inject CO2 into such a formation, which was located near Houston, Texas, offer a cautionary note on CO2 storage. They indicate that because CO2 makes the deep groundwater more acidic, metals in the sandstone get released. The results were reported in the journal Geology in July by the project’s geochemist, Yousif Kharaka of the U.S. Geological Survey, and his colleagues.

“We observed rapid dissolution of calcite and mobilization of large amounts of iron and other metals as a result of major drop of pH from 6.4 to 3,” Kharaka says. “These data are not a snag for CO2 storage in continental sedimentary basins,” he contends. However, the data do strongly suggest that CO2 injection wells should use acid-resistant cements and that abandoned wells should be avoided or monitored carefully.

“These former oil and gas wells were never engineered to last for a long time,” says Susan Hovorka, a geologist at the Texas Bureau of Economic Geology and the project’s principal investigator. She adds that another reason to avoid old wells is that most are shallow, because deeper is generally considered better for CO2 sequestration. The release of metals identified by Kharaka represents “a new element of risk, because it shows the potential for reactive chemistry that could be of concern,” says geologist Julio Friedmann at the Lawrence Livermore National Laboratory. “But these new results are not likely to present a substantial complication to underground storage,” he adds. This is because metal-bearing oxides and hydroxides usually make up <1% of saline aquifers and

EDIT

http://pubs.acs.org/subscribe/journals/esthag-w/2006/sep/tech/rr_co2.html

[Boomer]

1. Sigh

Even when we try to make it better, we make it worse.

[phantom power]

2. I knew there'd be a gotcha.

[JohnWxy]

3. interesting. Thanks for this post.

[mccoyn]

4. I'm waiting for the first baking soda protest. -nt

[Javaman]

5. Okay, I'm not a chemist, geologist or play one on tv, but...

once we capture CO2 is there a way to turn it into a solid other than dry ice?