In October 2024, a headline made waves across climate and tech circles: Ebb Carbon, a California-based startup, had inked a multimillion-dollar agreement with Microsoft to tackle a quietly growing crisis in our seas: ocean acidification. Using a futuristic technique called electrochemical ocean alkalinity enhancement (OAE), they want to restore the ocean’s natural ability to absorb carbon dioxide by tipping its chemistry back toward balance.
On paper, the idea is elegant. Ebb’s system mimics the Earth’s own carbon buffering process, adding alkaline substances like magnesium hydroxide to seawater to neutralize acid and increase the ocean’s capacity to draw down atmospheric CO₂. In a world struggling to reduce emissions fast enough, it’s a tempting solution. But it also opens up new and difficult questions about what happens when humans start rewriting the chemistry of the sea. It’s a step into uncharted territory.
While the science behind the method is rooted in chemistry, the stakes are deeply human. Since the start of the Industrial Revolution, average ocean surface pH has dropped by about 0.1 units, which might sound small, but in chemical terms represents a 30% increase in acidity. Nearly half of that drop has happened just since the 1980s. This has triggered a cascade of chemical changes in seawater that is now making it harder for shell-building creatures (like oysters, mussels, and corals) to survive.
For these organisms, the sea is becoming more corrosive. For us, it means that the scaffolding of entire ecosystems is dissolving. As pressure mounts on governments and corporations to meet long-ago promised net-zero targets, corporations are pledging potentially powerful tools in the climate action toolbox. Carbon removal credits, for example, are becoming a booming market with projections for it to grow from $2 billion in 2023 to over $50 billion by 2030. The idea that we can clean up the carbon mess with technological fixes is alluring. But it comes with a warning label.
As with many geoengineering approaches, the science is ahead of the policy — and in some cases, ahead of ecological understanding. “The jury’s still out on the damage that OAE could do,” says Dr. James Kerry, a coral reef expert at James Cook University. He and others worry about unintended consequences that could ripple through food chains.
One major concern is the risk of mineral precipitation, a process where added alkalinity causes dissolved calcium and carbonate ions in seawater to bond and form solid particles. These carbonate minerals, often appearing as whitish flakes or clouds, can sink and accumulate in the water column or on the seafloor.
At best, this reduces the efficiency of the carbon removal process by locking carbon into sediments instead of drawing it into long-term ocean storage. At worst? It creates ecological disturbances. Clouded water can reduce light penetration, which is a critical issue for photosynthetic marine organisms like phytoplankton, seagrasses, and corals. These organisms rely on sunlight to produce energy and disruptions to that light availability can suppress their growth, reduce oxygen production, and weaken the very ecosystems OAE technologies aim to protect.
“If the surface becomes murkier, we risk starving the base of the marine food web,” Kerry explains.
There’s also a biological risk that’s harder to quantify: particle ingestion by marine organisms. Tiny carbonate precipitates may be indistinguishable from natural plankton or detritus to filter feeders like mussels, oysters, and baleen whales. Ingesting these particles could cause digestive blockages or nutritional deficiencies.
While studies on this specific risk are limited, past research on microplastics and marine snow suggests that foreign particles in the water column can have sublethal but significant impacts on marine animals, particularly in early life stages. And the problem doesn’t end with individual species; if OAE disrupts the growth of certain phytoplankton species (the microscopic plants at the base of the oceanic food web), it can alter nutrient cycling, zooplankton populations, and fish recruitment rates. Entire fisheries, particularly in coastal regions that already face stress from warming and overfishing, could be affected.
Yet for all these concerns, there is no centralized or binding international regulatory body overseeing ocean alkalinity enhancement. Current laws under the London Protocol (which governs marine pollution from dumping) do mention ocean-based geoengineering, but only vaguely and with no enforceable guidelines for monitoring or accountability.
As a result, many OAE field trials are happening in regulatory grey zones, sometimes with little to no local stakeholder engagement. This is making some marine scientists uneasy, as Ebb is not alone. The field of marine carbon removal has seen explosive growth and in September 2024.
Planetary Technologies, a Canadian company, raised over $11 million in funding to pursue similar ocean alkalinity projects. Ebb also plans to scale up its current operations from under 100 tons to 1,000 tons of CO₂ removal per year at a new facility in Port Angeles.
“This plant will enable us to have confidence to then build much, much bigger plants,” CEO Ben Tarbell says. They want to remove 2 billion tons of carbon per year by building infrastructure into existing desalination plants. “We will not fix the entire bulk of the ocean, but we’ll be able to de-acidify the coastal ocean, which is where most of the life forms thrive.”
Still, others aren’t convinced that good intentions are enough. Dr. David Ho, Professor of Oceanography at University of Hawaiʻi at Mānoa, a co-founder and the Chief Science Officer of [C]Worthy, a non-profit that works on verifying ocean-based carbon dioxide removal, believes carbon removal efforts like ocean alkalinity enhancement shouldn’t be left solely in the hands of private companies.
“They have no way to prove that what they’re doing is effective – that’s a big problem,” Dr Ho said.
The crux of the dilemma, he explains, is that we are fighting a planetary-scale problem, but are doing it with tools that are still being built and tested. Geoengineering is not inherently good or bad, but it is inherently powerful. And power, especially when exercised in ecosystems as complex and fragile as the ocean, must be handled with caution.
Nature-based solutions like restoring seagrass beds, mangroves, and kelp forests offer a path that naturally sequesters carbon while supporting biodiversity, protecting coastlines, and feeding communities. Yet these habitats don’t attract the same level of venture capital as shiny silicon-and-steel solutions. That’s partly because they can’t promise the same quick, measurable carbon offsets that corporations seek.
In the end, the question isn’t just whether OAE works, it’s about who benefits, who decides, and who bears the risk. Tinkering with seawater chemistry might help draw down carbon and reduce ocean acidification in theory, but it also means changing the fundamental conditions under which marine life has evolved over millions of years.
Before we commit to scaling up, scientists like Kerry are calling for slow, transparent, and well-monitored pilot projects. Ones that, ideally, prioritize co-design with local communities and build adaptive policy frameworks alongside the science. Because once these interventions go global, it may be too late to undo the damage.