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.
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