CLIMATEWIRE | There is a growing consensus among climate scientists that, to avoid the worst effects of global warming, humanity must find a way to sequester carbon dioxide, and most efforts to date have focused on removing CO2 from the atmosphere.

But two ongoing efforts, including one from the Massachusetts Institute of Technology, have focused on the oceans, rather than the air. And if successful, scientists say the process could significantly reduce the cost of using carbon capture to combat global warming.

A big reason? “In the oceans, the capture step has already been done for you,” said T. Alan Hatton, a professor of chemical engineering and team leader at MIT, who published a report about his process this month in the newspaper Energy and Environmental Sciences.

That’s because the oceans are Earth’s main “carbon sink,” absorbing 30 to 40 percent of greenhouse gases from the atmosphere.

“In addition, the density of greenhouse gases in the oceans is more than 100 times higher than in the air,” Hatton added. “Which means that the volumes of material that need to be handled in ocean harvesting are much smaller than in air harvesting operations, further simplifying the whole process.”

The MIT report describes a two-step “electrochemical” process that extracts CO2 from seawater. The first step uses electricity to temporarily acidify the water, which encourages the removal of CO2. A second step removes the acidity and collects the CO2.

Kripa Varanasi, an MIT professor of mechanical engineering and co-author of the report, said in an interview that the MIT approach reduces energy costs and the expensive membranes used to collect CO2 to the point where diesel-powered merchant ships could collect enough CO2. to offset their emissions.

Other ships “could become the scrubber of the oceans,” he said, a step that could also attract small nations whose incomes depend on tourism, aquaculture and fishing industries that could otherwise be badly damaged by warming. of water caused by climate change.

MIT is one of two leading US efforts to explore the process of CO2 removal in the oceans. Earlier this month, Captura Corp.—a company spun off from the California Institute of Technology—issued a press release marking the start of its first pilot plant near Newport Beach, California, which is being designed to eliminate CO2 from the Pacific Ocean.

The company uses a process that relies on electrolysis and membranes to remove CO2 from seawater. It has received financial support from the Saudi Arabian Oil Co., which believes that its large collection of water desalination plants can be used for CO2 removal. It also received a $1 million grant from a carbon removal XPRIZE competition that is funded through a $100 million donation from billionaire Elon Musk.

Hatton said the MIT effort, which started later than Cal Tech’s, hopes to join the contest once it finishes its technology research within the next year. “Hopefully it’s just as good, if not better,” she said, noting that the MIT research began with a grant from the Department of Energy-Energy’s Advanced Research Projects Agency two years ago.

theXPRIZE, Billed as the largest incentive prize in historyit is designed to stimulate global competition between companies, governments and investors who can find effective ways to remove 10 billion metric tons of CO2 annually by 2050.

Final XPRIZE winners will be announced on Earth Day in 2025. The most promising removal technology will receive $50 million and the next three contestants will split $30 million.

What it means for the MIT effort is that the ultimate CO2 collection efforts need to be very large. Planners are thinking of converting CO2 into fuels like ethanol or products like concrete.

But underground geological storage areas, such as depleted oil reservoirs, are likely to get most of the ocean-derived CO2, Hatton said.

“You are not going to be able to use everything as raw material. You will run out of markets.” So, as he said, “a significant amount of the CO2 captured will need to be buried underground.”

Reprinted from E&E News with permission of POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environmental professionals.