May 29, 2013
New CO2 Removal Technique Produces Green Fuel, Offsets Ocean Acidification
April Flowers for redOrbit.com - Your Universe Online
A new technique to remove and store atmospheric carbon dioxide has been demonstrated by scientists at the Lawrence Livermore National Laboratory (LLNL). The new technique also generates carbon-negative hydrogen and produces alkalinity, which can be used to offset ocean acidification.At laboratory scale, the team demonstrated a system that uses the acidity normally produced in saline water electrolysis to accelerate silicate mineral dissolution. The system simultaneously produces hydrogen fuel and other gases. The electrolyte solution that results shows a significant elevation in hydroxide concentration that in turn proved strongly absorptive and retentive of atmospheric CO2. The findings of this study were published in a recent issue of PNAS.
The carbonate and bicarbonate produced in the process could be used to mitigate ongoing ocean acidification, the researchers suggest, much like 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, an LLNL visiting scientist, senior scientist at UC Santa Cruz (UCSC), said in a statement.
As carbon dioxide is released into the atmosphere, a significant fraction is passively taken up by the ocean. This fraction forms carbonic acid that makes the ocean more acidic. Many species, including corals and shellfish, are harmed by this acidification.
The Earth will likely warm by at least 3.6 degrees Fahrenheit by the middle of this century, and the oceans will experience a more than 60 percent increase in acidity relative to pre-industrial levels. The new process produces an alkaline solution that could be added to the ocean to help neutralize this acid and help offset its effects on marine biota. Further research is needed, however, according to the team, which included LLNL scientists Susan Carroll, William Bourcier, Michael Singleton, Megan Smith and Roger Aines.
"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," Rau explained. "But the process also would produce a carbon-negative 'super green' fuel or chemical feedstock in the form of hydrogen."
Previously described chemical methods of atmospheric carbon dioxide capture and storage are costly. Most use thermal/mechanical procedures to concentrate molecular CO2 from the air while recycling reagents, a process that is cumbersome, inefficient and expensive.
"Our process avoids most of these issues by not requiring CO2 to be concentrated from air and stored in a molecular form, pointing the way to more cost-effective, environmentally beneficial, and safer air CO2 management with added benefits of renewable hydrogen fuel production and ocean alkalinity addition," Rau said.
Further research is also 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, the team said.