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New LLNL technique for CO2 capture also produces green hydrogen and alkalinity to offset ocean acidification

Researchers at Lawrence Livermore National Laboratory (LLNL) have discovered and demonstrated a new technique to remove and store atmospheric carbon dioxide while generating carbon-negative hydrogen and producing alkalinity, which can be used to offset ocean acidification. A paper on their work appears this week in the Proceedings of the National Academy of Sciences.

The team demonstrated, at a laboratory scale, a system that uses the acidity normally produced in saline water electrolysis to accelerate silicate mineral dissolution while producing hydrogen fuel and other gases. The resulting electrolyte solution was shown to be significantly elevated in hydroxide concentration that in turn proved strongly absorptive and retentive of atmospheric CO2.

Further, the researchers suggest that the carbonate and bicarbonate produced in the process could be used to mitigate ongoing ocean acidification—similar to how an Alka Seltzer neutralizes excess acid in the stomach.

We not only found a way to remove and store carbon dioxide from the atmosphere while producing valuable H2, we also suggest that we can help save marine ecosystems with this new technique.

—Greg Rau, LLNL visiting scientist, senior scientist at UC Santa Cruz and lead author

When carbon dioxide is released into the atmosphere, a significant fraction is passively taken up by the ocean, forming carbonic acid that makes the ocean more acidic. This acidification—a direct consequence of increasing atmospheric CO2 concentrations independent of warming—has been shown to be harmful to many species of marine life, especially corals and shellfish. (e.g., Earlier post.)

Some projections suggest that global oceans could experience a more than 60% increase in acidity relative to pre-industrial levels by mid-century. The alkaline solution generated by the new process could be added to the ocean to help neutralize this acid and help offset its effects on marine biota. However, further research is needed, the authors said.

When powered by renewable electricity and consuming globally abundant minerals and saline solutions, such systems at scale might provide a relatively efficient, high-capacity means to consume and store excess atmospheric CO2 as environmentally beneficial seawater bicarbonate or carbonate. But the process also would produce a carbon-negative super-green fuel or chemical feedstock in the form of hydrogen.

—Greg Rau

Most previously described chemical methods of atmospheric carbon dioxide capture and storage are costly, using thermal/mechanical procedures to concentrate molecular CO2 from the air while recycling reagents, a process that is cumbersome, inefficient and expensive.

The new LLNL process avoids most of these issues by not requiring CO2 to be concentrated from air and stored in a molecular form, Rau said.

The team concluded that further research is needed to determine optimum designs and operating procedures, cost-effectiveness, and the net environmental impact/benefit of electrochemically mediated air CO2 capture and H2 production using base minerals.

Other Livermore researchers include Susan Carroll, William Bourcier, Michael Singleton, Megan Smith and Roger Aines.

Resources

  • Greg H. Rau (2011) CO2 Mitigation via Capture and Chemical Conversion in Seawater. Environmental Science & Technology 2011 45 (3), 1088-1092 doi: 10.1021/es102671x

Comments

sd

If we had abundant renewable electricity or even sufficient nuclear power, we would not need to burn coal, etc and the problem of excess atmospheric CO2 would go away. There is not indication of the scale that this technology would need to be to for it to be effective but it has to be enormous.

ai_vin

@sd

Actually we would still need it to undo the damage already done; http://www.skepticalscience.com/co2-residence-time.htm

All-in-all, CO2 capture, green hydrogen and alkalinity to offset ocean acidification make this technology a win, win and win.

SJC

CO2 accumulates in the air for 100 years, it does not go away. This way you can have offshore wind turbines making electricity to take the CO2 out of the water, make the carbonate and H2. Use the H2 and CO2 to make synthetic fuels, sequester carbon and make the ocean less acid. Sounds good to me.

John McAvoy

"If we had abundant renewable electricity" We DO have abundant renewable electricity technology. We just do not have the storage and distribution of it worked out. Ocean based conversion systems work when the supply permits wind blows, sun shines, waves undulate and/or current travels.

Davemart

I wouldn't bet the farm on this technology panning out, but is serves to show that those advocating that hydrogen should be ignored and total reliance placed on batteries are at least premature.

None of us know how the various technologies will work out, or the details of how we can make things work.

Silverthorn

I'm having a little trouble understanding the chemistry here. I don't see how it's possible to produce hydrogen gas from seawater without producing a corresponding volume of either oxygen and / or chlorine. The article is behind a pay wall, so I can't check it. Did the summary simply fail to mention the oxygen or chlorine?

There's a very efficient way to do most of what they're talking about: electrodialysis splits a volume of seawater into an acid portion and a base portion. The acid portion is then neutralized by dissolution of silicate minerals; the base portion is diluted and released into the ocean to counter acidification and pull CO2 from the atmosphere. Very energy efficient, in part precisely because it doesn't produce hydrogen gas.

Engineer-Poet
I don't see how it's possible to produce hydrogen gas from seawater without producing a corresponding volume of either oxygen and / or chlorine.

The anions appear to be reacted with a convenient mineral in an accelerated weathering process, converting the anions to dissolved bicarbonate.  This is not as good as converting to carbonate, but it's better than carbonic acid.

A D

Im interested to buy hydrogen and a hydrogen conversion for my old car.

Henry Gibson

Nothing really new here. The ocean will never become acidic in the lifetime of the earth, but it will become less alkaline and the comments that the ocean is x times more acidic than it was can be true without the ocean being acid at all, and the same thing can be said of a glass of sodium bicarbonate which will still fizz and release CO2 with acid addition and still measure alkaline. Planting trees is still the best means of capturing CO2. Giant kelp forests are also good and they should be cultivated in more places including the Salton sea. Please remember that Oxygen is poisonous and that before plants filled the skies with oxygen, CO2 was much more abundant. Nature still puts over 80 percent of the CO2 into the air. Growing trees without harvesting them and using the methane, now being wasted, for automotive fuel will reduce human CO2 releases faster and more economically than any possible renewable fuel. Co-generation of electricity with heat capture for heating or cooling is also a very fast and economical was of reducing CO2 releases by human economies. Well engineered fission reactors can produce cheap enough energy to Capture CO2 and concentrate it to be combined with Hydrogen produced by the energy from the reactor as well for the production of liquid fuels. A geothermal version of this is already operating in ICELAND. ..HG..

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