Can green hydrogen production help bring oceanic dead zones back to life?

Green hydrogen production makes a lot of extra oxygen. Could we put it to work revitalizing the ocean?
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So-called green hydrogen is made by using renewable energy to split water molecules into hydrogen and oxygen. DepositPhotos

This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at

Douglas Wallace was on a research ship in the middle of Canada’s Gulf of St. Lawrence when he heard the news: Canadian Prime Minister Justin Trudeau had met with Olaf Scholz, the German chancellor, in nearby Stephenville, Newfoundland. At their meeting in August 2022, the two leaders locked in Canada’s commitment to supply Germany with hydrogen gas. They chose to declare the “Canada-Germany hydrogen alliance” in Stephenville because the town is the site of the proposed World Energy GH2 project, a facility that will use wind power to produce hydrogen gas.

The announcement allowed the world leaders to demonstrate the shared goals of increasing the availability of so-called green hydrogen and of reducing Germany’s reliance on Russian oil. But for Wallace, the news triggered a different idea.

At sea, Wallace, an oceanographer at Dalhousie University in Nova Scotia, was tracking how dissolved oxygen moves from the Atlantic Ocean through the gulf into the St. Lawrence River, and how the dearth of oxygen in some places can lead to the development of low-oxygen dead zones. In particular, he was concerned with one extra big and persistent dead zone that had taken up residence near Rimouski, Quebec, along the outlet of the St. Lawrence River. So when he heard that Canada was set to ramp up hydrogen production—achieved by electrically splitting water molecules into hydrogen and oxygen—he wondered: could all of that spare oxygen help bring the dead zone back to life?

For those who live on land, it’s easy to take abundant oxygen for granted. But underwater, persistent patches of low oxygen are “a fundamental control on habitat,” says Wallace.

As the world warms, the oceans are losing their oxygen. Since the 1950s, they’ve already lost about two percent—a figure that could hit four percent by the end of this century. The loss can be caused by excess nutrient runoff, as with the vast dead zone at the mouth of the Mississippi River in the Gulf of Mexico, and by changes in ocean circulation driven by climate change—the likely culprit in the Gulf of St. Lawrence.

Too little oxygen in the water can reduce the diversity of marine life as animals either leave the area or die. In the Gulf of St. Lawrence—where the size of the dead zone has grown nearly sevenfold since 2003 to encompass roughly 9,000 square kilometers—dropping oxygen levels are already affecting many commercially important and at-risk species, such as cod, halibut, and northern shrimp, Wallace says. “About 15 percent of the deeper parts of the Gulf of St. Lawrence are getting close to the threshold where a lot of marine animals will struggle to live,” he says.

Currently, scientists can do little to fix oceanic dead zones. In smaller bodies of water, such as lakes and reservoirs, managers can pump oxygen-rich water from the surface into oxygen-poor deep areas. But the ocean is way too big to be artificially churned. Maybe, thought Wallace, he could take the oxygen created during hydrogen production and somehow pump it into the gulf.

His calculations suggest that it could work. The proposed Stephenville plant would produce more than enough oxygen to replace what the gulf loses each year. And Wallace’s experiments tracking how oxygen moves through the region show that oxygen pumped into the gulf near Stephenville would reach the Rimouski dead zone several hundred kilometers away within a few years.

Sean Leet, CEO of World Energy GH2, says the company is actively investigating uses for the oxygen produced by the hydrogen plant and that he’s met with Wallace to discuss the idea. The company would support further research and discussions around how it might work in practice, he says.

Even with Leet’s interest, however, the viability of Wallace’s oxygenation scheme is far from certain.

For starters, Wallace’s plan relies on the existence of large-scale hydrogen production. While the Stephenville plant seems to be on track to be built, Mark Winfield, who studies sustainable energy and climate change at York University in Ontario, says that, in general, the hydrogen market has an iffy future. The market “is smaller than some think, and the transition to hydrogen will be harder than they think,” he says.

Hydrogen fuel cells are still extremely expensive, Winfield says, and in many ways—such as the rush to decarbonize transportation—hydrogen has already lost the race. Hydrogen as a fuel makes the most sense for large industrial applications that cannot easily be electrified such as cement and steel production. But at present, no hydrogen-powered steel plants have been built. “The market is not at all mature, and there has been no increase in demand,” says Winfield.

In many cases, he says, rather than using renewable electricity to produce hydrogen, it’s probably better to just send that power to the grid.

Leet, however, counters that there is potentially a big market for hydrogen in Europe—particularly in Germany, the Netherlands, and Belgium—with applications in steel manufacturing, heavy industry, aviation, and marine fueling. “Their demand for clean fuels far exceeds what Canada and other countries will be able to supply,” he says.

Beyond the big questions about the future of hydrogen manufacturing, pumping dead zones full of oxygen would also require overcoming many lingering engineering challenges and environmental concerns, says Wallace. This includes figuring out how exactly to capture the oxygen and deliver it to the deep ocean. But Wallace says these are not insurmountable challenges; companies already do something similar in lakes on a much smaller scale.

Wallace also wants to determine what effect pumping large amounts of oxygen into the water would have on the local ecosystem and figure out how to fine-tune a process with a years-long lag between adding the oxygen and having it arrive at the dead zone. “We’d really want to do a small, controlled pilot before rushing in,” says Wallace.

And while the companies producing hydrogen would likely welcome a market for oxygen, a potentially valuable byproduct with no clear buyers, it’s unclear how it could generate revenue for them. Wallace suggests some form of credit, similar to carbon credits, but all the details would need to be worked out.

Despite the uncertainty, Wallace thinks it’s an avenue worth pursuing. “There are risks, but there are also risks to parts of the ocean becoming uninhabitable,” he says. “These are difficult questions, but we can’t avoid asking them, especially if there is a chance we can do something about it.”

This article first appeared in Hakai Magazine and is republished here with permission.