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Deep-sea sediments could safely store man-made carbon dioxide
MIT
Deep-sea sediments could provide a virtually unlimited and permanent reservoir for carbon dioxide, the gas that has been a primary driver of global climate change in recent decades, according to a team of scientists that includes a professor from MIT.
The researchers estimate that seafloor sediments within U.S. territory are vast enough to store the nation’s carbon dioxide (CO2) emissions for thousands of years to come.
“The exciting thing about this paper is that we show that CO2 injected beneath the seafloor is sequestered permanently,” said Charles Harvey, an associate professor in MIT’s Department of Civil and Environmental Engineering. Harvey is a co-author of a paper on the work that appears in this week’s issue of the Proceedings of the National Academy of Sciences.
“CO2 injected underground on land is buoyant, and hence has the potential to escape back to the surface,” Harvey said. “This is not the case under the deep ocean. Because the ocean floor is so cold, liquid CO2 stored beneath the floor is denser than water and will not rise to surface. Furthermore, the top of the injected CO2 plume will form a hydrate, an ice-like solid that plugs up the pore spaces, ‘self-sealing’ the injected CO2 plume into the deep sea sediments.”
(7 Aug 2006)
Sounds wonderful, except that the energy costs of such a process are not discussed. Merely capturing carbon dioxide will come at an energy cost, meaning that more fuel will need to be burnt. Building the infrastructure and transporting that carbon dioxide out to deep water oceans will come at another large energy cost, reducing the energy returned on invested (ER/EI), thus increasing again how much fuel is used — if that is, the ER/EI is still above one at all.
-AF
Burying the evidence of global warming (carbon sequestration in lava flows)
Don Vergano, USA Today
…Carbon sequestration would be fine for the Midwest, where there are plenty of sandstone layers, but not so great for the Pacific Northwest and Southeast, which lack them, says environmental scientist B. Peter McGrail of the Pacific Northwest National Laboratory in Richland, Wash. His team reports another solution for those states in perhaps the least likely of locations — under the hardened lava of old volcanic eruptions.
In a study accepted for publication in the American Geophysical Union’s Journal of Geophysical Research-Solid Earth, McGrail and colleagues report that ancient lava flows, perhaps 10 million years old in Washington State, sandwich deep basalt rock layers that would keep carbon dioxide thoroughly bottled up. “A simple fact of the physics of lava flows” reliably creates these layers, McGrail says, about 3,000 feet deep. Just like baking bread, bubbles in lava flows become trapped between the cooling outer crust, making the interior of a lava layer permeable.
Most surprising, the stone within those water-filled layers appears to mix with carbon dioxide to form solid rock, the team reports, alleviating worries about the gas leaking away once it is buried. The process starts within a year to three year’s time of injecting the carbon dioxide, astonishingly fast by geological standards. “Essentially we are making limestone,” McGrail says.
(20 Aug 2006)
Needed: A Price on Carbon
David Talbot, MIT Technology Review
Sequestration technology is increasingly ready for prime time, but the required policy lags behind, says MIT expert Howard Herzog.
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Pumping carbon dioxide underground on a massive scale has been talked about for years; the idea is to “sequester” the greenhouse gas so that it won’t enter the atmosphere and contribute to global warming and climate change.
Technology Review asked Howard Herzog, an MIT chemical engineer and program manager of the Carbon Sequestration Initiative, an industrial consortium, for his take on the subject.
His appraisal of the state of sequestration: first, the geological questions are being resolved favorably; second, without policies that put a price on carbon, it is unlikely that more sequestration facilities will actually get built.
The United States is the world’s leading carbon dioxide emitter, but the Bush administration opposes regulating carbon dioxide. Herzog says he expects the technology case for carbon sequestration to be further solidified in the next few years, in time for the next administration in Washington to take action.
(14 Aug 2006)
