Can we effectively remove carbon dioxide from the atmosphere to mitigate ocean acidification? A recent test shed light on this as a research team injected 65,000 liters of alkaline sodium hydroxide into the Gulf of Maine in August 2025.

“We were pioneers in exploring the enhancement of alkalinity using a ship,” stated Adam Subhas from the Woods Hole Oceanographic Institution in Massachusetts. The team shared their preliminary findings at the Marine Science Conference on February 25th in Glasgow, UK. “It’s clear we observed increased CO2 absorption due to this experiment.”

Over the span of four days, the team indicated that between 2 to 10 tons of CO2 were extracted from the atmosphere, with a potential total of up to 50 tons. Importantly, no adverse effects on marine ecosystems were noted.

Nonetheless, Subhas highlighted a critical point: the team hasn’t calculated the emissions produced during the manufacturing and transport of the sodium hydroxide, leaving the net CO2 removal outcome uncertain. “That’s an essential area for future research,” he remarked.

The ocean acts as a significant carbon sink, storing 40 times more carbon than the atmosphere and absorbing over a quarter of the excess CO2 emitted. This surplus CO2 reacts with ocean water to create carbonic acid, leading to increased ocean acidity.

Ocean acidification can severely impact various marine organisms by dissolving carbonate shells, thereby diminishing the ocean’s carbon absorption capacity.

Researchers are actively investigating numerous strategies to counteract ocean acidification, such as adding magnesium hydroxide to wastewater, spreading crushed olivine on beaches, and transporting seawater to onshore treatment facilities. Some companies are even marketing carbon credits based on alkalinity enhancement.

“This is indicative of current private sector initiatives,” Subhas explained, emphasizing the need for non-commercial trials like their team’s.

Given the sensitive nature of such experiments, the team engaged local stakeholders, particularly the fishing community. “Establishing a two-way dialogue is crucial,” asserted Kristin Kreisner of the Environmental Defense Fund, a New York-based nonprofit.

The testing involved three ships and was meticulously monitored using various methods, from satellites to floating sensors and ocean gliders. Sodium hydroxide was mixed with a trace dye called rhodamine to accurately track its dispersion.

The researchers measured concentrations of microorganisms, plankton, fish larvae, and lobster larvae, as well as photosynthetic activity levels. According to Rachel David at Rutgers University, New Jersey, “Our trials did not significantly impact the biological community.”

The additional carbon introduced into the ocean through increased alkalinity converts into bicarbonate ions, akin to dissolved baking soda. “We anticipate this carbon will remain locked for tens of thousands of years, making it one of the most sustainable carbon removal methods,” Subhas noted.

The nature of this process allows CO2 to be removed and stored simultaneously, providing benefits over other methods that necessitate separate CO2 capture and permanent storage.