INTERVIEW: Direct ocean carbon removal startup declares technology advantage over DAC

Captura asserts its direct ocean carbon capture technology is more efficient than direct air capture for meeting net-zero emissions by 2050, with plans to secure an offtake agreement for its first commercial plant by year-end.

The company's direct ocean capture system extracts carbon dissolved in seawater using "curtailed and off-peak" renewable electricity. It employs proprietary electrodialysis and gas extraction technologies to remove CO2 for permanent storage or reuse.

"The hardest challenge with carbon removal is that CO2 in the atmosphere is very thinly dispersed at 420 parts per million," Captura CEO Steve Oldham told Platts July 18. "To capture CO2 at the massive scales that we require, you need to move a lot of air, you need to touch a lot of air."

This complexity makes carbon dioxide removal difficult, which is why Captura and other climate and engineered solutions are expensive today, Oldham added.

"It's easy to buy some cheap [carbon] credits from finite sources today, but that's not helping us collectively solve the problem of 10 billion [mt/CO2e] per year," he said. "If you buy our credits, you're buying into a solution that has considerable scalability without the need for imported material or waste products."

According to the World Economic Forum, to achieve the UN IPCC net-zero target by 2050, up to 10 billion mt of CO2 must be removed from the atmosphere annually. Currently, CDR achieves 2 billion mt/CO2e per year, primarily driven by nature-based projects.

Oldham said it remains uncertain whether cheaper small-scale CDR technologies can meet this target and if enough biomass is available for its production. However, he noted that "the CDR problem will be solved by multiple technologies working together, rather than an individual solution."

Leveraging ocean's capacity for effective carbon removal

"We let the ocean do the hard work of removing CO2 from the air," Oldham said.

The ocean, covering 70% of the Earth's surface, serves as a highly effective carbon removal device. Due to Henry's Law, CO2 is 50 times more concentrated in the ocean than in the air, offering a scalable and efficient method to remove atmospheric CO2, Oldham added.

Henry's Law states that the amount of gas dissolved in a liquid at a constant temperature is directly proportional to the gas's partial pressure upon it, explaining how CO2 is absorbed by the ocean.

Compared to other carbon removal technologies, Captura operates as a closed-loop system, requiring no absorbents or chemicals and producing no waste. The water outflow meets wastewater standards for pH level, alkalinity, oxygen, and dissolved substances, Oldham added.

"By removing CO2 from the ocean, you reduce ocean acidification and prevent the outgassing of CO2 when you remove it from the atmosphere," Oldham said. This approach also addresses coral reef bleaching, rising ocean temperatures, and impacts on marine life.

Scalable deployment at lower cost than DAC

The technology can be deployed onshore at facilities that intake ocean water, such as power plants that use seawater for cooling. It can also be implemented on offshore infrastructure, including large vessels or oil and gas platforms repurposed at the end of their field life. Lastly, dedicated platforms next to the ocean, Oldham said.

Captura provides a solution functionally equivalent to DAC, producing a stream of CO2 that is fully measurable, utilizable, and sequesterable. However, carbon capture is done where carbon concentration is higher and easier to capture, Oldham said.

The company's CDR technology is certified under Isometric's Direct Ocean Capture & Storage protocol. Captura previously announced a 30,000 mt offtake agreement with Mitsui O.S.K. Lines, Ltd.

"Our very first [commercial] plant at small scale will be about half the price of the first DAC plants," Oldham said. "A lot of the economics around how DAC expects its cost to drop is through [...] scale and repetition by building many plants, we can get to between $100 and $150 mt/CO2e with less than 3 megatons of installed capacity."

Platts last heard carbon removal credits for DAC were in the range of $350-$1,000/mt, depending on contract type, tenure and volume, with most being tied to long-term contracts due to the upfront capital requirement.

Despite its potential, DAC technology has faced criticism for slow cost reduction and unmet deliveries, though some projects are expected to bridge the technology's learning curve, like Deep Sky, others like 1PointFive, are expected to be operational this year.

"We have a high degree of confidence that we will be close to the CDR $100/mt target set by the Department of Energy," Oldham said, acknowledging the need to address power requirements and proximity to the sequestration site.

To achieve scale, Captura plans to increase the volume of its degassing processes and increase its modular and proprietary electrodialysis systems, Oldham said.

Currently, Captura's focus, besides operating its 1,000 mt/CO2e pilot plant in Hawaii, is to build its first commercial plant. "We anticipate that we will secure the offtake for that before the end of the year," Oldham said.

Platts, part of S&P Global Energy, assessed US biochar prices, also within the tech-carbon removal segment, for current-year delivery at $145/mtCO2e on July 24, holding a $5 premium to credits sourced from India.