FOr for four days last August, a thick maroon film marred the waters of the Gulf of Maine. The scene was no different from toxic red tide, the result of 65,000 liters of alkaline chemicals tagged with red dye that scientists intentionally injected into the ocean.
As cynical as it may sound, the event was part of a scientific experiment that could advance technology to combat both global warming and ocean acidification. This approach is called ocean alkalinity enhancement (OAE) and works like natural weathering, but on an anthropogenic rather than geological time scale.
“The ocean is already incredibly alkaline, with 3800 billion tonnes of carbon stored as dissolved bicarbonate, or baking soda,” says Adam Subbas, lead oceanographer on the research team who presented initial results of the experiment at the AGU Marine Science Conference in Glasgow.
Increasing this natural alkalinity using chemical antacids should, in theory, allow the ocean to absorb more carbon. Combined with rapid emissions reductions across large surface areas, OAE could prevent global temperatures from rising 2°C above pre-industrial levels, while locally reducing ocean acidity, which is currently higher than at any time in the past million years and poses a serious threat to marine life and fisheries.
The experiment, sanctioned by the U.S. Environmental Protection Agency and supervised by scientists at Woods Hole Oceanographic Institution, took place 80 miles off the coast of Massachusetts in areas commonly fished for cod, haddock, and lobster.
Although small, their study, which has not yet been peer-reviewed, showed promising results. Over five days at sea, the Loc-ess project used state-of-the-art technology, including autonomous gliders, long-range autonomous underwater vehicles, and shipboard sensors, to track 65,000 liters of sodium hydroxide, an alkaline chemical tagged with a red dye, as it left the release site.
During this period, they measured up to 10 tons of carbon entering the ocean and an increase in the local pH at the deployment site from 7.95 to 8.3. This indicates that ocean alkalinity has returned to pre-industrial levels. The experiment did not show any significant harm to organisms such as plankton, fish or lobster larvae, but the researchers did not measure effects on adult fish or marine mammals.
The experiment was conducted 80 miles off the coast of Massachusetts in an area where cod, haddock, and lobster are commonly fished. Photo: Sebastian Zeck
Some people think it is reckless to use chemicals to solve environmental problems. “What we’re seeing is a movement toward greater control over natural systems,” says Benjamin Day, senior climate and energy justice activist at Friends of the Earth. Mr Day said he was “deeply concerned” about the environmental impacts of OAEs occurring on a large scale, including the risk of “unintended and catastrophic consequences”.
But whether we like it or not, we are already experimenting with the climate in uncontrolled ways. “We really need to think about this from a stewardship perspective,” said Phil Renforth, a carbon dioxide removal (CDR) expert at Heriot-Watt University in Edinburgh. “We’re adding carbon dioxide to the atmosphere every year, and much of it ends up in the ocean. And the real question is, can we be proactive about how we manage it?”
In fact, OAE is very similar to lime and was first used by Greek farmers 2,000 years ago to neutralize acidity in their fields. More recently, in the 1980s, large doses of alkaline lime were administered to Scandinavian rivers suffering from fish declines due to acid rain. Reported successes include the return of native salmon to Sweden’s Etland River.
There are already a number of OAE startups confirmed to sell carbon credits through Isometric, an international carbon removal registry. These credits are being purchased by companies aiming to claim their business as net zero.
However, it is still unclear whether OAEs can safely function at the levels needed to provide climate benefits. Subhash’s team, which includes researchers from Woods Hole Oceanographic Institution, Rutgers University and the Environmental Defense Fund, will be the first to test it on the high seas.
Their plan now is to use ocean data to model how chemical plumes continue to absorb CO2 over time. “In the best-case scenario, this diffusion would result in about 50 tons of carbon dioxide being taken from the atmosphere into ocean water over about a year,” Subhas says. For comparison, 50 tonnes of carbon is equivalent to the annual emissions of five British citizens.
If that sounds boring, that’s because the team has no commercial ambitions for OAE, so they started small to demonstrate best practices in a rapidly evolving field. “If these experiments need to be done, we want them to be done by respected, objective, transparent research institutions that are making a real effort to engage and involve us in the process,” says Sarah Schuman, a commercial fisherman who joined the research team as an observer at sea.
Prior to participating, Schuman attended five of 50 meetings that scientists conducted in person with fishermen, tribal leaders, and stakeholders along the Massachusetts coast to address local concerns in advance of field testing.
Schumann said that while local fishers have experience working with researchers and generally trust the science, “there was a big concern that this could be a Trojan horse for other players to come in,” noting the fact that commercial operators are keen to show that OAE is effective and therefore eligible for carbon credits.
Schuman is not alone in this concern. “There are a lot of companies racing ahead of this,” Day says. “And those companies are being promoted by some technology companies that are very keen to offset their emissions.”
However, if OAE is to scale as a meaningful technology, it will likely require private and public investment. The National Oceanic and Atmospheric Administration says it could remove 1 billion to 15 billion tonnes of CO2 a year at a cost of up to $160 (£120) per tonne.
“There aren’t many places on Earth that can store carbon,” Renforth said. “Nothing should be thrown off the table until we have a viable solution for the entire space.”
