This story was originally published by Inside Climate News and appears here as part of the Climate Desk collaboration.

The ocean is quite literally a massive sink for carbon. Research shows that this body of water has absorbed more than a quarter of all carbon dioxide pollution that humans have pumped into the sky, helping to prevent more catastrophic impacts from climate change than the ones humanity is already experiencing.

However, scientists have found that even the ocean is reaching its limit, and could become only half as efficient at sucking in carbon by 2300 due to extreme warming and acidification. But a growing number of startups, including Captura and Running Tide, have pledged to help lighten the ocean’s carbon load by using technology to suck the greenhouse gas directly from seawater.

In one of the biggest efforts yet, carbon removal company Equatic and Singapore’s national water agency PUB announced that they have set out to build the world’s largest ocean-based carbon removal plant. Last year, the company — owned and run by scientists from the University of California, Los Angeles — developed two proof-of-concept pilots in L.A. and Singapore, which successfully extracted around 100 kilograms (0.1 tons) of carbon dioxide each day.

Now, their goal is to develop a $20-million plant that removes 3,650 metric tons (4,000 tons) of the gas from the ocean annually, according to a UCLA press release.

How does it work?

In the “Equatic process,” operators start by running an electrical current through seawater pumped into the facility. This charge separates water (H2O) into hydrogen and oxygen, and then air is passed through the water, which traps and stores CO2 in solid calcium and magnesium-based materials “similar to how seashells are naturally formed,” reported Time, which named Equatic as one of the “Best Inventions of 2023.” Removing carbon from the water enables the ocean to absorb more carbon from the air, the company says. In addition to storing CO2, the company plans to use the hydrogen byproduct as an ingredient in clean fuel, according to the statement. Other companies have been testing different processes to suck carbon from seawater, which my colleague Ananya Chetia wrote about last year.

But does it work?

Technically yes, but the scalability of this seemingly magical process of sucking carbon from the air or sea has been met with widespread skepticism by scientists. More than 200 experts signed a letter in September outlining their concerns:

#Singapore to build world’s largest facility that sucks #carbon from the sea. #ClimateChange #CarbonCapture #Seawater #GHG #ClimateGoals

“While ocean-based carbon dioxide removal approaches have enormous potential, there are also risks,” they wrote. “Society does not yet have nearly enough information about the effectiveness or impacts of any specific approach and so cannot make informed decisions about their use at scale.”

Last May, a UN panel called the carbon capture industry “unproven,” with “unknown” risks, and questioned its economic viability due to high operating costs. But the U.S. government is certainly making big bets on research that will help enhance the ocean’s ability to remove carbon from the atmosphere. In October, the Department of Energy (DOE) allocated $36 million in funding to “advance marine carbon dioxide removal techniques” (Equatic is not part of this initiative, but has received funding from the DOE). The National Science Foundation took the first steps toward launching a federal research program to investigate different techniques such as using “minerals and electricity to change the alkalinity of the oceans to allow seawater to absorb more CO2 from the air,” E&E News covered.

Many experts agree that carbon capture is going to be necessary to meet climate goals. The new Equatic plant is a “significant part of Singapore’s goal to reach net-zero emissions by 2045,” writes Koh Ewe for Time. If the plant meets its expected output, the company plans to scale up at a commercial level, and has already entered agreements with other businesses, including Boeing, to purchase carbon credits — a practice that has also faced its fair share of controversy, as my colleagues have explored several times in the past.

Keep reading

The antidote to this egregious form of techno- optimism is contained in just one word written in it: Scalability.

This is not a Star Trek movie where magical solutions abound.

The basic thing here is that when they talk about electrolysis of water to get hydrogen, it is generally noted that it takes a lot of energy and so the hydrogen is very expensive. So, this is the same process, but with some CO2 capture as a bonus, which is nice, but the bottom line remains: You're pouring a lot of energy into that seawater.

Once we have replaced all the coal and natural gas with ample cheap renewable electricity, something like this might not be a bad idea. Right now, I think building the renewables in the first place is a better use of money. And certainly if you're using electricity generated by natural gas to electrolyze seawater and sequester a bit of CO2, you are releasing more CO2 (and methane) than you're removing. And unless you're in somewhere like British Columbia, or you have your own solar panels, some of your electricity does come from fossil fuels; you can say "No, I have a contract that says I'm just buying wind powered electricity" but it's sophistry--the mix is the mix, and even if you could sort the actual electrons so that was literally true, which you can't, your increased use of wind-powered electrons means someone else is using more fossil-fueled electrons. So as of right now, this is a "solution" that risks releasing more CO2 than it sequesters, which would be really stupid.

Meanwhile, under current conditions I'm not sure how this is supposed to make money. Unless you can arrange to get paid a LOT for that CO2 and that hydrogen, the power is going to be too expensive for you to break even.

"Right now, I think building the renewables in the first place is a better use of money."

It's already in the works, which puts the H2 thing even more questionable:

>>The Australia–Asia Power Link (AAPowerLink) is a proposed electricity infrastructure project that is planned to include the world's largest solar plant, the world's largest battery, and the world's longest submarine power cable.<<