Various decarbonization technologies are emerging and evolving. Some will be more feasible and effective than others, but as scientists, we should keep an open mind. Some of these technologies utilize “direct capture” which has its own supporters and critics. This edition of Core Elements reports on two recent studies on this topic.
Rasoul Sorkhabi
Editor, Core Elements
Out of Thin Air
Chayanuphol/Shutterstock.com
This is the title of a recent article in Scientific American, referring to direct air capture (DAC). Many of us have heard of DAC, but not many people know that the technique came from a teenage girl’s sixth-grade science class project.
Background:
In 1997, 11-year-old Claire Lackner asked her physicist dad, Klaus Lackner, for a science project idea.
Klaus, then working at Los Alamos National Laboratory, suggested trying to capture carbon dioxide from the air.
Claire got an aquarium pump and forced air through a test tube of sodium carbonate, which then combined with carbon dioxide. Overnight, about 10 percent of CO2 from the air sample was removed.
Claire won a prize for her science project, and her dad wrote a paper about the procedure.
In 2007, Klaus co-founded the Global Research Technology Corp. to engage in DAC business.
During the 2008 financial crisis, Klaus’ company went out of business, but his concept is still alive today.
The recent boom: Since the 1950s, sorbent technologies have removed suffocating carbon oxides from the air in submarines and spaceships. But recently, this tech has taken off.
The recent DAC boom has been fueled by governments and companies prioritizing public image and their “social license to operate,” major tax breaks to corporations, and billion-dollar funding for research and the development of several regional DAC hubs in the United States.
Additionally, oil and gas companies trying to offset their carbon footprints are buying carbon credits from DAC companies.
Start-up players: Several start-up companies are engaged in developing and refining DAC technologies.
Heirloom Carbon in California’s Silicon Valley is the first U.S.-based commercial DAC company.
It was founded by two young engineers in 2020 who raised $53 million from a group of investors, including Bill Gates.
In 2023, the U.S. Department of Energy awarded Heirloom Carbon and its Irish counterpart Climeworks up to $600 million to build a DAC hub in Louisiana.
How it works: My colleague Sarah Compton, who writes AAPG’s Enspired newsletter, recently shared more about Heirloom’s technology.
Pros and cons of DAC:
DAC could be a good solution for CO2 emission sources that are difficult to eliminate or perform point-source capture, such as agriculture, air or sea travels, and cement and steel production.
Critics, however, say that CO2 is too dilute (420 ppm) in the atmosphere for DAC projects to be effective.
Currently, DAC costs up to $1,000 per metric ton of CO2—many times higher than point-source carbon capture or simply tree planting.
Some petroleum companies such as Occidental do see value in DAC.
Go deeper: Read the Scientific American article online. Also, check out Klaus Lackner’s June 2010 article “Washing Carbon Out of the Air” in Scientific American.
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A recent article in Science reports on start-ups engaged in direct capture of CO2 from ocean waters.
Context:
The world’s oceans absorb about 25 or 30 percent of carbon dioxide emitted into the atmosphere from human activities. Excess CO2 in the oceans causes ocean acidification with adverse impacts on marine ecosystems.
DOC players: The Science article introduces several start-up companies in the DOC space, including two Los Angeles-based companies, Captura and Equatic, as well as San Francisco-based EbbCarbon, Netherlands-based SeaO2, and Israel-based CarbonBlue.
How it works: Captura’s technology involves the following steps:
Sea water is piped into a reactor, which uses electricity to split water into positive and negative hydroxyl ions.
The ions react with sodium and chloride ions to form hydrochloric acid and sodium hydroxide.
Hydrochloric acid reacts with bicarbonate ions, causing carbon dioxide to bubble out into a storage tank.
Sodium hydroxide is added to the seawater to neutralize the acid.
Seawater is then discharged back into the ocean.
Limitations:
While the DOC procedure is successful in small pilot plants, scaling it to efficient and massive carbon dioxide removal is a challenge.
Unlike DAC, which enjoys a tax credit of $180 per ton of sequestered carbon, DOC does not currently qualify for tax credits.
Advantages:
Carbon dioxide concentrations in oceans are 150 times higher than in the air.
Researchers hope that DOC will cost less than $100 per ton of carbon, compared to $600–1,000 cost of DAC.
Thank you to all who responded to last week’s quiz question!
Last week’s question was: Why are rare-earth elements called by that name?
Here is a great answer from Herbert Vogler in California:
“Rare earth elements are called rare because they’re rarely found concentrated in large and easily accessible deposits, making their extraction and mining challenging, despite their relative abundance compared to other elements such as gold or silver. ‘Earth’ refers to their occurrence in oxide minerals that may be dissolved in acid.”
Now, for this week’s question: Why do clay minerals swell when very wet and shrink when very dry?
Please send your response by November 14 to editorial@aapg.org (subject line: Core Elements Quiz).
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