Takeaways from AP report on company that sold 200,000 carbon credits to remove CO2 from ocean

Associated Press

03-07-2025

Formed three years ago, Gigablue says it has designed particles that when released in the ocean will trap carbon at the bottom of the sea. Gigablue says its work will do nothing less than save the planet.
But outside scientists frustrated by the lack of information released by the company say serious questions remain about whether the technology works as the company describes. Their questions showcase tensions in an industry built on little regulation and big promises.
Here are highlights from The Associated Press' reporting:
What is Gigablue?
Gigablue, founded by a group of entrepreneurs in Israel, was originally named 'Gigaton' after the one billion metric tons of carbon dioxide most scientists say will be necessary to remove from the atmosphere each year to slow global warming.
The company began trials in the South Pacific Ocean last year, and says it will work with country authorities to create a 'sequestration field' — a dedicated part of the ocean where 'pulses' of particles will be released on a seasonal basis.
The company announced earlier this year that it reached a historic milestone: selling 200,000 carbon credits. It's the largest sale to date for a climate startup operating in the ocean, according to the tracking site CDR.fyi, making up more than half of all ocean-based carbon credits sold last year.
How do the carbon credits work?
Carbon credits, which have grown in popularity over the last decade, are tokens that symbolize the removal of one metric ton of carbon dioxide from the atmosphere. On paper, companies that buy credits achieve a smaller carbon footprint without needing to reduce their own emissions — for instance, by paying another vendor to plant trees or capture carbon dioxide from the air.
Only a few countries have required local industries to purchase carbon credits. Most companies that buy them do so voluntarily.
The credits have helped fund a band of startups like Gigablue that are eager to tackle the climate crisis, but they are also unevenly regulated, scientifically complex, and have in some cases been linked to fraud.
Gigablue's 200,000 credits are pledged to SkiesFifty, a newly formed company investing in greener practices for the aviation industry.
Gigablue wouldn't reveal what it earned in the sale, and SkiesFifty's team declined to be interviewed. Most credits are sold for a few hundred dollars each — but a chart on Gigablue's website suggests its prices are lower than almost any other form of carbon capture on the market.
How does Gigablue's technology work?
The particles Gigablue has patented are meant to capture carbon in the ocean by floating for a number of days and growing algae, before sinking rapidly to the ocean floor.
Algae has long been attractive to climate scientists because it absorbs carbon dioxide from the surrounding water as it grows. If the algae sinks to the deep sea or ocean floor, Gigablue expects the carbon to be trapped there for hundreds to thousands of years.
The ultimate goal is to lower carbon dioxide levels so drastically that the ocean rebalances with the atmosphere by soaking up more CO2 from the air. It's a feat that would help slow climate change, but one that is still under active study by climate scientists.
What are Gigablue's particles made of?
While Gigablue has made several commercial deals, it has not yet revealed what its particles are made of. Partly this is because the company says it will build different particles tailored to different seasons and areas of the ocean.
'It's proprietary,' said chief technology officer Sapir Markus-Alford.
Documents provide a window into the possible ingredients. According to information on the permit, Gigablue's first New Zealand trial last year involved releasing particles of pure vermiculite, a porous clay often used in potting soil.
In the second New Zealand trial, the company released particles made of vermiculite, ground rock, a plant-based wax, as well as manganese and iron.
A patent published last year hints the particles could also be made of scores of other materials, including cotton, rice husks or jute, as well as synthetic ingredients like polyester fibers or lint.
The company said it had commissioned an environmental institute to verify that the particles are safe for thousands of organisms, including mussels and oysters.
What do outside scientists say?
Several scientists not affiliated with Gigablue interviewed by the AP said they were interested in how a company with so little public information about its technology could secure a deal for 200,000 carbon credits. The success of the company's method, they said, will depend heavily on how much algae grows on the particles, and the amount that sinks to the deep ocean. So far, Gigablue has not released any studies demonstrating those rates.
Thomas Kiørboe, a professor of ocean ecology at the Technical University of Denmark, and Philip Boyd, an oceanographer at the University of Tasmania who studies the role of algae in the Earth's carbon cycle, said they were doubtful algae would get enough sunlight to grow inside the particles.
It's more likely the particles would attract hungry bacteria, Kiørboe said.
The rates at which Gigablue says its particles sink — up to a hundred meters (yards) per hour — might shear off algae from the particles in the quick descent, Boyd said.
It's likely that some particles would also be eaten by fish — limiting the carbon capture, and raising the question of how the particles could impact marine life.
Boyd is eager to see field results showing algae growth, and wants to see proof that Gigablue's particles cause the ocean to absorb more CO2 from the air.
In a statement, Gigablue said that bacteria does consume the particles but the effect is minimal, and its measurements will account for any loss of algae or particles as they sink.
The company noted that a major science institute in New Zealand has given Gigablue its stamp of approval. Gigablue hired the National Institute of Water and Atmospheric Research, a government-owned company, to review several drafts of its methodology.
In a recent letter posted to Gigablue's website, the institute's chief ocean scientist said his staff had confidence the company's work is 'scientifically sound' and the proposed measurements for carbon sequestration were robust.
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This story was supported by funding from the Walton Family Foundation. The AP is solely responsible for all content.
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