Monday, March 03, 2008

Carbon Dioxide: Let's Put It Under Stuff!

With nearly carbon-negative alternatives, like GreenFuel's Emissions-to-Biofuels technology, it's slightly painful to see well-meaning scientists and organizations like Bruce Yardley and the Natural Resources Defense Council still arguing in favor of "carbon capture and storage (CCS)," a process by which carbon dioxide is "caught" from coal- or natural gas-fired power plants and then "stored" in (wait for it...) caves.

Since Yousif Kharaka's study (.pdf file) for the U.S. Geological Survey revealed that leaking CO2 from CCS could acidify surrounding water, leach metals, and endanger both wildlife and public health—all before escaping back into the atmosphere anyway—there really isn't too much to recommend this new research. From Discover:
[A] British geologist’s study suggests sandstone could rapidly absorb [CO2] potentially providing a safe, leakproof reservoir. Last year, Bruce Yardley, a professor at the University of Leeds in England, was monitoring oil extraction at a BP oil field in the North Sea. To speed the oil’s flow to the surface, seawater had been pumped to the bottom of the wells. When Yardley analyzed a sample of the injected water, he found it rich in silica. That signaled that the water and minerals in the surrounding sandstone had reached a chemical equilibrium with the injected seawater far more quickly than anticipated—in two years rather than a century.

Past studies had shown that when carbon dioxide is injected into sandstone, it dissolves common carbonates in the rock, changing the chemistry of sitting water and making a carbonic acid that eats holes in the rock. This can lead to CO2 leakage. Based on the speed of the silicates’ reaction with seawater, Yardley believes that when CO2 is injected into high-silicate minerals like feldspar, it too will quickly react, making clays and carbonates that clog the pores of the rock and trap the gas.
This, incidentally, is basically a radically less energy-intensive version of mineral storage techniques, which is good. However, you don't get biofuels out of it, so WGAF?

[Link to the Discover magazine article; Related a neat MSNBC video of MIT's Isaac Berzin who came up with GreenFuel's method for making both ethanol and biodiesel from CO2-fed algae]

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