Imagine a remote, rocky island with a huge chemical plant that extracts acid from the ocean, pours it onto the island’s rocks, and lets the runoff drain into the ocean.
It might sound at first like some mad scientist’s scheme. But it’s actually a serious plan by Harvard researchers for pulling carbon dioxide, the primary greenhouse gas, out of the air. The chemical process would lock up CO2 in the form of chalk that would be buried naturally at sea, so it could help lower carbon dioxide levels in the atmosphere and fight climate change.
Harvard researchers have an idea to exploit ocean chemistry to lower levels of greenhouse gases. (Source: Flickr)
The amount of carbon dissolved in the oceans depends on the acidity of the water; if the oceans were less acidic, they would be able to take up more CO2. Kurt House, a Harvard graduate student in the earth and planetary sciences department, and colleagues have devised a way to remove acid from the ocean to drive and speed up this process.
“It’s a form of geoengineering, changing the chemistry of the oceans, in order to pull CO2 out of the air,” says House.
Carbon to chalk
The first step is to draw water from the sea and run it through an electrochemical plant. It would use electricity to drive reactions that pull hydrochloric acid out of the ocean. This in turn would enhance the ocean’s natural ability to soak up carbon dioxide and store it in the form of bicarbonate.
Over hundreds or thousands of years, the bicarbonate would react further to form insoluble calcium carbonate—or chalk—that would become buried under the ocean floor.
To neutralize the acid from the ocean, the plant would run it over rock, producing sand and salt that can be safely disposed of. The procedure would resemble natural processes of rock weathering, but put into overdrive.
Energy sink
However, the process requires a lot of energy to drive the electrochemical reactions. Unless it’s powered by low-carbon electricity—from wind, geothermal, or natural gas—it would be counterproductive. So the Harvard team proposes putting the chemical plants in remote regions where they could harness wind or geothermal energy that would otherwise go untapped.
One major question is how much the process can be scaled up. Even under the most optimistic projections, at most it could reduce about 10 percent of current CO2 emissions, says Michael Aziz, a Harvard materials scientist who worked with House on the idea. “So we can’t relax and all go out and buy SUVs,” he adds.
“Their process seems basically feasible,” says Ken Caldeira, a climate scientist with the Carnegie Institution for Science in Stanford, CA. “I think it’s relatively benign for the oceans.” He adds, however, “the main drawback is that it’s very energy intensive, so it’s likely to be very expensive.”
Peter Brewer, an ocean chemist with the Monterey Bay Aquarium Research Institute in California, is more circumspect about the idea. “It is a bit of a stretch—perhaps an A-plus for ingenuity and a C for practicality,” he says. One problem is that the process involves a number of complex steps that haven’t been shown to be manageable on large scales. “I doubt very much that this can be practical and cost effective,” Brewer says.
Pros and cons
Climate scientists have studied other ways of spurring the ocean to absorb more carbon dioxide, such as “fertilizing” it with iron to stimulate the growth of plankton, which take up CO2. House’s proposal would certainly cost more and require more energy, Caldeira says. But, he points out, “fertilization of the ocean with iron seems to be limited to, at most, absorbing about 2 percent of current emissions.” House’s idea is, in principle, more scalable and won’t interfere as much with natural ecosystems, he says. And, he adds, since it would work by reducing the acidity of seawater, it could counteract ocean acidification, a side effect of rising atmospheric CO2 levels that threatens marine life.
Despite the challenges, Aziz and House are pushing the idea forward. They say that a financial incentive to sequester carbon is first needed. “If and when a carbon tax or cap-and-trade system [for greenhouse gas emissions] creates a high enough price for carbon emissions, the story will be different,” Aziz says.
I struggle mightily with geoengineering research such as this, or other popular ‘solutions’ like iron fertilization. The problem is that is gives people a false sense of faith that science will ‘cure’ global warming. Instead, above all else, people need to realize that for real change to happen without significant unintended consequences (e.g. the chalk factories will use a LOT of energy and create waste), we need to change our lifestyles. This is increasingly problematic when governments push these types of programs over conservation or sustainable resource management.
Nick—
Most of the credible researchers I’ve heard support more research into geoengineering stress the point that it’s generally easier, cheaper, and better for the planet to cut back emissions in the first place. They’re worried, too, that even just talking about geoengineering schemes—none of which have been proven to work yet—will create complacency among the public. That’s why Aziz pointed out that he could see the chalk process tackling only a fraction of the CO2 problem, and said “we can’t relax and all go out and buy SUVs.”
All of the well known researchers I’m aware of who support research on geoengineering do so not as an alternative to changing our lifestyles and our whole energy system. They do so because they worry that people won’t change quickly enough, or that those changes simply won’t be enough and we may have to reduce CO2 levels below what they already are at today, to avoid dangerous climate change.
I haven’t heard of any governments pushing any sort of geoengineering scheme, let alone pushing one as an alternative to conservation or sustainable resource management. But if you have heard of governments making noises along these lines (as your message implied), let me know, since I’d be interested to hear what they’re saying.
Every respected researcher who talks about geoengineering agrees that these approaches could have significant unintended consequences. That’s why they’re supporting more research into these approaches, so they can get a sense of what the consequences might be, and see which ones might be real options.
For this chalk approach, using a lot of energy is not an intended consequence; it’s an essential part of running the process, and something the researchers factor in to figure out whether this is feasible. But it’s possible that this approach could disrupt marine life, so Aziz wants to study that, first in the lab and then on a small scale in the ocean, to see whether it stills seems attractive or not.
Hi Mason, thanks for your comments. I enjoyed reading the article. I’ll just add a few comments to what you said:
I agree that the researchers themselves probably a) believe people cannot change fast enough to avoid causing serious harm to the planet, and b) do not see geoengineering as an alternative to conservation. I commented because, to me, the tone of the article implied that the researchers were more interested in inventing a new ‘save-all’ technology instead of actually assessing if it will really be feasible in the future, all of the other consequences considered. That might be their job as scientists/engineers, but it’s only part of the story. I might have read it too fast and missed something, but that was just my impression. The point on the SUV’s is important, and certainly a step in the right direction.
I do think this research is interesting, but I wish there was equal time (in science, the media, funding) devoted to what is being done to tackle the ‘people’ part of the problem as opposed to solving climate change with technology. Obviously, that is an incredibly difficult task, and one that attacks our very way of living. How can we as people be smart about the environment while tackling human rights/poverty issues? Do scientists have a role in addressing these problems? This post in Samuel Frankel’s blog highlights one scientist who believes so.
I think I ‘misspoke’ on my governments pushing geoengineering. I do not know of any governments implementing these plans, but carbon sequestration research is a big area of funding by the U.S. DOE right now, and I expect it will only get bigger even with lack of increased DOE funding for fundamental science (especially if a financial incentive to sequester carbon, like your article mentioned, becomes strong enough).