alkalinity

About 30% of the carbon dioxide emitted by human activity is absorbed by the oceans. As a result, they are getting warmer and more acidic, and the currents that help shape global weather are shifting. To try to reduce global warming, people want to be able to store even more carbon dioxide in the oceans without the negative effects of doing so.

There are multiple efforts across the globe to achieve effective marine carbon dioxide removal. Some are based on sinking carbon-rich materials to the bottom of the sea. This is the marine equivalent of capturing CO2 from the air and storing it underground. Other efforts involve increasing the alkalinity of the ocean, which increases its ability to chemically react with carbon dioxide as well as lowers its acidity, which is desirable in many ways.

Running Tide, a U.S.-based company, has been dumping thousands of tons of wood-industry waste 190 miles off the coast of Iceland. The company has also been experimenting with dumping algae and kelp and sinking it deep below the ocean. Such materials on land either get burned or decay, in both cases releasing CO2 into the atmosphere. On the deep-sea bottom, the carbon is trapped.

Other efforts involve pumping seawater through electrodialysis filter systems to remove excess acidity or adding alkaline rocks to increase water alkalinity.

All of these efforts are a form of geoengineering, and like proposed ideas to cool the atmosphere, pose potential risks. There is no silver bullet to solve the climate crisis. It will take a combination of many solutions to address the issue of excess carbon dioxide in the atmosphere. Marine carbon dioxide removal is one of the solutions that may play a role.

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Scientists Are Trying to Coax the Ocean to Absorb More CO2

Photo, posted February 22, 2018, courtesy of Bobbie Halchishak/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

There is increasing concern that reducing carbon emissions alone will not be sufficient to stabilize the climate and that technologies that actively remove carbon dioxide from the air will be needed. There has been a fair amount of analysis of the efficacy of storing carbon in agricultural soil and in forests, but there has not been comparable studies of the risks, benefits, and trade-offs of ocean-based strategies.

The oceans currently absorb about a quarter of the world’s carbon dioxide emissions. There are multiple ways in which oceans could be induced to store much more. A new report from the National Academies of Sciences, Engineering, and Medicine looks at several ocean carbon dioxide removal strategies in terms of efficacy, potential costs, and potential environmental risks.

One approach involves adding nutrients to the ocean surface to increase photosynthesis by phytoplankton. The approach has a medium to high chance of being effective and has medium environmental risks.

Another approach is large-scale seaweed farming that transports carbon to the deep ocean or into sediments. It has medium efficacy chances but higher environmental risks.

Protection and restoration of coastal ecosystems including marine wildlife would have the lowest environmental risk but only low to medium efficacy.

Chemically altering ocean water to increase its alkalinity in order to enhance reactions that take up carbon dioxide would be highly effective but a medium environmental risk.

The report describes some other approaches as well. It recommends a $125 million research program to better understand the technological challenges as well as the potential economic, social, and environmental impacts of increasing the oceans’ absorption of carbon dioxide.

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Oceans Could Be Harnessed to Remove Carbon From Air, Say U.S. Science Leaders

Photo, posted August 21, 2016, courtesy of Quinn Dombrowski via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.