A recent scientific report from the National Academies of Sciences, Engineering and Medicine (USA) recommended a research project to study in detail how the ocean could be exploited in order to increase CO2 sequestration and, in doing so, mitigate anthropogenic climate change.
One of the ways to combat global warming is to deliberately intervene on the climate in order to limit its drift. This is called geoengineering. Among the many techniques proposed is the artificial exploitation of the oceans in such a way as to increase the absorption of carbon dioxide (CO2) and thus reduce its concentration in the atmosphere.
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Given the huge reservoir that the ocean represents, the method can prove to be very effective. However, questions continue to arise regarding possible risks, various angles of approach or the precise measurement of benefits. For these reasons, a scientific report produced by the United States recently recommended a dedicated research program that should take place over ten years and with a budget of some $ 125 million.
“All land-based approaches have limitations, so it’s important to evaluate the possibility of using the oceans as well,” says report co-author Romany Webb. “It is important to note that the report identifies not only the key scientific questions that need to be answered, but also social, legal, regulatory and political issues”.
A range of more or less expensive, more or less risky routes
In order to stimulate the absorption of CO2 by the ocean, six avenues are advanced in the document. These include nutrient fertilization, the cultivation of algae, the restoration of ecosystems, the increase of the alkalinity of the waters, electrochemistry, and finally the dives and lifts of artificial waters. It should be noted that for most of these methods, carbon is captured not by surface waters themselves, but by marine life. By sedimenting, the organisms then transfer it to the deep ocean and the solid Earth.
As for the research costs, they range from 100 to more than 300 million dollars depending on the technique under consideration. The most expensive is the one based on electrochemistry and the least expensive, the one involving the ascent and diving of the waters. It should be noted that the risks associated with each method may differ by several orders of magnitude, the lowest being those related to the restoration of the ecosystem. Nevertheless, it is necessary to take a similar look at the effectiveness, cost and disadvantages in order to objectively assess the benefit/risk ratio.
“Strategies for removing carbon dioxide from the oceans are already being discussed by scientists, non-governmental organizations and entrepreneurs as potential climate response strategies,” says Scott C. Doney, lead author of the report. “At present, society and policy-makers do not have the information they need to assess the impacts and trade-offs”. This is a gap that this report aims to bridge by calling for the implementation of a dedicated research program.