Interest is growing in removing carbon from the oceans

Brad Ack understands why people might be wary of sinking billions of tons of carbon pollution into the ocean, using nascent technologies to tackle the climate crisis.

However, record levels of global warming have put the planet and the ocean in such danger that aggressive, large-scale measures are essential, said Ack, executive director of Ocean Visions, a nonprofit coalition that promotes ocean climate solutions. .

“The oceans have very significant potential to help and be part of the gigantic carbon removal challenge that we have,” Ack said. “The ocean is already the largest carbon cycler on the planet.”

Even the near elimination of emissions from burning fossil fuels by 2050 will not be enough to cool the planet’s overheated ocean system or completely alleviate the rise in wildfires, droughts or floods, Ack said.

The United Nations Intergovernmental Panel on Climate Change (IPCC) has made clear a series of Carbon dioxide removal (CDR) strategies are needed. to meet the international goal of limiting warming to 1.5 C.

Carbon removal, also known as negative emissions strategies, includes natural solutions such as relying on forests, marshes or soil to trap and store carbon, or deploying emerging technology to extract carbon directly from the air or ocean and then store it long term. .

The estimates suggest between five and 16 billion tons of CO2or 16 GtCO2 (gigatonnes), must be eliminated annually between now and 2050, depending on the rate of emissions reduction and whether we exceed our climate objectives.

It’s not a question of whether we remove carbon, but where we do it, Ack emphasized.

The ocean is already the largest carbon sink on the planet, absorbing 30 percent of man-made emissions and 90 percent of excess heat generated by greenhouse gases. Able to retain CO2 in the deep sea for hundreds and even thousands of years, the oceans act as a reservoir for approximately 38 GtCO2 of this “blue carbon”.

Attention and controversy are increasing over climate solutions that aim to scale up and accelerate the ocean’s natural biological or chemical processes to capture and store C02.

The ocean sequesters CO2 in two ways: when microscopic sea creatures or plants absorb carbon and when carbon dioxide dissolves in the ocean.

Phytoplankton at the ocean surface extract carbon and release oxygen during photosynthesis. They can be eaten by other animals or die and fall to the ocean floor where they become trapped in sediment.

Surface water also absorbs and dissolves carbon. The colder and less salty the water, the more dissolved carbon it can absorb. Ice water near the poles tends to absorb more CO2 and, being denser, sinks to the sea floor, moving with deep ocean currents under pressure toward sea basins over long periods of time.

There is growing interest in marine carbon dioxide removal (mCDR) solutions, which aim to scale up and accelerate the ocean’s natural biological or chemical processes to capture and store CO2, Ack said.

Amplifying natural blue carbon storage through the conservation and restoration of marine ecosystems such as mangroves, seagrasses or salt marshes with overall benefits for biodiversity has broad support in the scientific community and is underway around the world.

However, there is a schism among researchers, some of whom fear novel strategies that have not yet been tested on a large scale.

Emerging ocean-based strategies are being considered to remove carbon and address global warming. Illustration by Ocean Visions

Proposals include massively boosting the production of algae such as kelp, which absorb carbon during photosynthesis, before sinking it into the deep sea or converting it into climate-friendly seafood or bioplastic.

Others involve pumping surface water deep into the ocean, where increased pressure and solubility allow more carbon to be stored. Or, alternatively, pushing cold, nutrient-rich water from the depths to stimulate the growth of carbon-absorbing plankton before sinking into deeper waters when they die.

A related strategy is to fertilize the ocean with iron or nitrogen to trigger large plankton blooms.

Clean carbon from the air or removing it from the ocean water Methods are also being explored before injecting it into the depths or seafloor, or increasing the ocean’s alkalinity and its ability to absorb carbon by loading it with minerals such as basalt or carbonate.

Critics suggest that focusing on novel methods represents a distraction from the urgent and drastic emissions cuts and nature-based solutions that are currently viable.

and a number of marine scientists with the Deep Sea Ocean Stewardship Initiative urge caution when using the deep sea as a potential dumping ground without a solid understanding of the impacts on ocean chemistry, food webs and marine life.

Professor Lisa Levin of the Scripps Institution of Oceanography at the University of California, San Diego, led a team study on how manipulating the ocean to curb the climate crisis could threaten deep-sea ecosystems or their vital carbon cycle services.

Decomposing algae on the seafloor could deplete oxygen and pumping excess carbon dioxide into the deep sea could suffocate marine life.

Sowing the ocean with alkalinity-increasing substances or plankton could reduce light, cause harmful levels of cadmium or nickel, destructive algal blooms, or increase ocean acidity.

“The technologies are virtually unproven,” he said. There is a concern that if people think about the ocean, they think about it in the wrong way: as a waste disposal system,” she said.

More research and integrated policies are needed to ensure that the costs of mCDR do not outweigh the benefits, he said.

Brad Ack, CEO of Ocean Visions, spoke about the need to advance science on ocean carbon removal at the recent UN Climate Summit in Dubai. Photo courtesy of Ocean Visions.

Ack agreed, noting that Ocean Visions has created a plan to accelerate science and actions needed to prove or disprove the feasibility of new ocean carbon removal methods by 2030.

“We are a consortium of scientific organizations trying to ask and answer the most critical questions about whether or not this can be scaled and whether we can do it safely and effectively, and how that compares to all the other alternatives,” Ack said.

To date, the focus on carbon cleanup has been on natural, terrestrial solutions, which simply cannot deliver the important carbon removal needed, Ack said.

Two billion tons of CO2, or two gigatonnes (GtCO2), are removed annually, the vast majority using conventional land-based methods such as forest protection or restoration or soil management. recent research indicates.

Only one percent of that total comes from emerging technologies such as direct air capture and storage (DAC).

However, natural terrestrial carbon removal, even scaled up to five GtCO2 by 2050, will not be enough on its own to reach net zero.

It is estimated that novel methods, including ocean-based options, should provide half of the 10 GtCO2 removals needed by mid-century. Those strategies must increase to approximately 15 GtCO2 by the end of the century.

There will undoubtedly be trade-offs in large-scale interventions, but the climate crisis is now immune to tentative interventions, he said.

It is analogous to using chemotherapy, which has unpleasant symptoms, to treat a lethal cancer, he added.

Global warming is on the way to becoming increasingly dangerous for life, he stressed.

“We know it and we see it in our real lives,” Ack said.

“Now the question is: how many different forms of medical intervention are we willing to try to stay alive?”

Rochelle Baker / Local Journalism Initiative / Canada’s National Observer

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