What is blue carbon and how can it help fight climate change?
Blue carbon is becoming an increasingly popular term, but what does it really mean? The answer may vary slightly depending on who you ask.But broadly speaking, according to State Oceanic Administration“Blue carbon is just a term for carbon captured by the world’s oceans and coastal ecosystems.”
So why is it important? What role can it play in fighting climate change?To find out, we spoke to researchers at the Columbia Climate Institute Dorothy Petit, Agis Subramanimand Roman Weber Some opportunities and challenges about working with Carbon from marine and coastal ecosystems.
Conservation and Utilization of Blue Carbon
Scientists are exploring blue carbon in two main ways. First, they want to measure and preserve the carbon already stored in oceans and coastal wetlands such as swamps and mangroves. Second, they want to know how we can use these ecosystems to mitigate climate change.
Dorothy PetitSenior Research Scientist, NASA/Goddard Institute for Space Studies, Adjunct Professor, Columbia University Department of Earth and Environmental Sciences, is trying to solve the first riddle.She and her colleagues are Lamont-Doherty Earth Observatory Carbon content in local swamp sediments is being measured.
“Despite their relatively small size, salt marshes store about 50 times as much carbon as terrestrial forests,” she said. “This carbon is at risk as sea levels rise, and if the swamps are flooded, it will lead to warming greenhouse gases in the atmosphere.”
Looking up over the sediment, subramaniamresearch professor and oceanographer at the Columbia Climate Institute Lamont Doherty Earth Observatory, focusing on the organisms that live in these ecosystems and their ability to store carbon. “Populations in the ocean, seagrasses and microalgae store a lot of carbon and grow along the coast. So you want to make sure that any coastal development or construction or human activities like shrimp farming or aquaculture don’t end up releasing this carbon ,”He said.
Learn has shown wetland shop Accounting for 20 to 30 percent of the world’s carbon emissions, this figure is especially impressive compared to the relatively small land surface they cover.
Oceanographer Ajit Subramaniam deploys marine robotics on an ocean research expedition. Photo: Ajit Subramaniam
Protecting wetlands with captured carbon is critical, but we can’t stop there, Subramaniam continued, noting that the more important way we think blue carbon might be is by pulling carbon from the atmosphere.
“When you go offshore, many of the proposed schemes for removing carbon from the atmosphere start by growing kelp – which absorbs carbon dioxide during photosynthesis – and then harvesting it. Again, you can take different paths: you The kelp can be eaten or repurposed. Or you can sink it in a durable way and bury it,” he said.
Subramaniam believes in repurposing kelp — with food Or biofuels – not enough to address the urgency of climate change, because once kelp is consumed or burned, the carbon goes back into the atmosphere. “If you think about green biodiesel, it’s great, and it’s another way to bend the emissions curve downward. But it doesn’t actually reduce the emissions rate or the amount of carbon in the atmosphere.” That’s a first step, but “use Replacing diesel with biodiesel “can’t be the end goal,” he said.
Another option, Subramaniam said, is to sink the kelp to the depths of the ocean for at least 100 years, so the carbon captured by photosynthesis doesn’t cycle back into the atmosphere. Ideally, over the course of that century, you also buy time for scientists and engineers to come up with new and better technologies.
“We already have models that help us figure out how deep we need to sink carbon, and how long it stays there. But when you do that, you’re affecting a different ecosystem, which also It needs to be considered,” he said.
“Nature Based Solutions”
For one of his current projects, Subramaniam has come up with what he calls a “nature-based solution” for removing carbon, sinking sargassum macroalgae 2,000 meters below the ocean’s surface. Sargassum is a pelagic macroalgae, which means it spends its entire life cycle at the surface of the ocean, where it is visible to the naked eye. “It never clings to land and doesn’t come ashore unless it washes ashore and runs aground.”
Close up view of Sargassum seaweed on Crane Beach, Barbados. photo: Collected via Creative Commons
While this macroalgae has been known for centuries, in the past 10 or 20 years, new populations have moved closer to the equator, Subramaniam said. “They call it the ‘Great Sargassum Belt,’ and it basically runs from the coast of West Africa all the way to the Gulf of Mexico in the Caribbean to the coast of Mexico. It’s a major nuisance.”
He added that the kelp had piled up on the beaches of the Windward Islands in the Caribbean, wrecking an economy largely dependent on tourism. “How do you get rid of it? You can’t bury it. You can’t take it off the beach and put it anywhere on land because the islands are so small.”
Instead, Subramaniam and his colleagues hope to use advanced technologies, including remote sensing, artificial intelligence and marine robotics, “to drive a series of platforms that pull the nets about 15 or 20 miles offshore so that they can be harvested in the Sargassum seaweed.” Catch them before they reach the ocean. Beach.”
An illustration of the Subramaniam project, which uses advanced remote sensing, modeling, and marine robotics to remove carbon dioxide from the atmosphere while mitigating the economic and ecological harm caused by sargassum.Images courtesy of Caroline Juang, courtesy of Ajit Subramaniam
He explained that once the net is filled with the macroalgae, it bursts, and when that happens, there is a fastener on the net that is used to close it. Fasteners attach weights that will then sink the sargassum to 2,000 meters, which means “we’re going to completely stop this carbon cycle,” he says.
“There’s about a million tons of carbon in this ‘new’ Sargassum population,” Subramaniam said. As a conservative estimate, he thinks they could sequester at least 10 percent of the carbon, or about 100,000 metric tons per year, using the proposed technology. “In context, orca facility In Iceland, the largest carbon capture plant has the capacity to absorb 4,000 metric tons from the atmosphere each year. “
Of course, one of the important points to consider when coming up with this approach is carbon life cycle analysis. “For example, you can’t consume 100 kilograms of carbon to absorb 10 kilograms of carbon. We need to make sure that we don’t consume more carbon in sinking than we sink,” he said. They want the use of remote sensing, robotics and artificial intelligence to maximize efficiency.
Subramaniam notes that he is personally “deeply skeptical of geoengineering,” but because the sargassum population in question is new—and thus likely already linked to human activity and climate change—he’s comfortable with removing it.
he also with WeberAssociate Research Fellow, Deputy Director, Columbia University School of Law Sabin Center for Climate Change LawStudy the legal aspects of this process, as it falls within the gray area of ​​existing environmental law.
legal and social considerations
Romany Webb researches the legal issues associated with the development and deployment of land and sea negative emissions technologies.
“I think there are a lot of unanswered scientific questions about the role of blue carbon in climate change mitigation,” Weber said, spending a lot of time thinking about technologies for removing and storing carbon dioxide from the atmosphere, and what those frameworks mean in order to ensure that they Happens in a safe and responsible manner.
But in addition to scientific issues, there are social and governance issues that could affect whether we can effectively use any proposed strategy, she added. “We may oppose projects because they are seen as unnatural or disturbing marine ecosystems, which many believe are the last untouched parts of the planet, or because they are seen as affecting other marine life activities. Some groups Concern was also expressed that since the projects would be carried out in the oceans, which are part of the global commons, they might be subject to limited oversight and control by national governments.”
She said that while a great deal of international law applies to ocean activities, there is no comprehensive international legal framework specific to ocean carbon removal technologies, leading to a lot of uncertainty. For example, ocean fertilization and ocean alkalinity enhancement, which add substances to water, can be considered a form of ocean dumping with an established international legal framework.
“However, the framework was developed to address issues like dumping oil into the ocean,” she said. Also, as Subramaniam points out in his project, “In this case, you’re transferring what’s already in the ocean to another place.”
Another challenge, Webb added, is that domestic law is more likely to emerge the closer to shore, creating potentially overlapping frameworks. “In the U.S. in particular, domestic law can include multiple layers of government because you might have federal, state, or even local laws. So, there are questions about how different activities will be dealt with and how they will fit into existing frameworks that were not really developed for carbon removal. A lot of complexity and uncertainty.”
Next step
Weber and her colleagues at the Sabin Center are currently writing a book examining these existing international and national legal frameworks and how they apply to different Ocean-based carbon removal activities. In addition to studying U.S. law, they collaborate with legal scholars in six other countries (China, Canada, Germany, Norway, the Netherlands, and the United Kingdom). title – Ocean CO2 Removal for Climate Change Mitigation: Legal Framework— will be published this spring.
At the same time, Weber and her colleagues at the Sabin Center were also writing a set of model law For ocean carbon dioxide removal projects. “We hope to draft model legislation that could be enacted by Congress to create a comprehensive legal framework specific to ocean carbon dioxide removal research,” she said. Areas covered by the document will include: federal jurisdiction over ocean carbon dioxide removal projects, whether responsibility for overseeing this research is solely federal or whether states have a role to play, which agencies should issue permits, and what factors they consider in doing so There are considerations when doing so, and what the environmental review and public consultation process for research projects should look like.
“We hope to publish draft model legislation in early 2023,” Webb said.
Through these initiatives, the experts hope to bring more clarity to scientists, lawmakers, and the public about the growing field of blue carbon research.
