Scientists have demonstrated a new technique to capture and store atmospheric carbon dioxide, generating carbon-negative hydrogen and producing alkalinity, which can be used to offset ocean acidification.
The Lawrence Livermore team's system uses the acidity produced in saline water electrolysis to accelerate silicate mineral dissolution while producing hydrogen fuel and other gases, reports Phys.org. The resulting electrolyte solution was shown to absorb and retain atmospheric CO2.
A significant portion of atmospheric carbon dioxide is absorbed by the ocean, forming carbonic acid, making the ocean more acidic. By the middle of this century, the oceans will experience a more than 60 percent increase in acidity relative to pre-industrial levels.
With further research, the alkaline solution generated by the new sequestration process could be added to the ocean to neutralize this acid and help offset its effects on marine life.
"But the process also would produce a carbon-negative 'super green' fuel or chemical feedstock in the form of hydrogen," said Greg Rau, an LLNL visiting scientist, senior scientist at UC Santa Cruz and lead author of the paper published in the Proceedings of the National Academy of Sciences.
"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 said.
Most prior methods for atmospheric carbon dioxide capture and storage proved cumbersome and costly, using thermal/mechanical procedures to concentrate molecular CO2 from the air while recycling reagents.
"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.
The authors called for further research on scale designs, and the net environmental benefit, if any, of electrochemically mediated air CO2 capture and H2 production using base minerals.