Storing carbon in the form of gas hydrates deep under water

The Bay of Bengal and the Indian Ocean have been identified as potential carbon sinks due to the presence of gas hydrates at depths exceeding 2,800 meters. This discovery has significant implications for India's efforts to achieve its national decarbonization and climate change objectives by 2030. However, the technologies required to harness this potential are still in the early stages of development and necessitate adequate funding for further testing and implementation.

The report outlines seven potential strategies based on the ocean to reduce emissions, including the extraction of marine carbon dioxide, and the storage of carbon under the seabed. Other options involve expanding ocean-based renewable energy; reducing emissions from ocean-based transportation; protecting and rehabilitating coastal and marine ecosystems; utilizing low-carbon food sources from the oceans; decreasing emissions from ocean-based tourism; and minimizing offshore oil and gas activities.

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A report from the World Resources Institute suggests that these 'biotic' or biological-based methods can help oceans absorb carbon by utilizing photosynthesizing organisms in seawater to capture carbon dioxide and store it as biomass. For instance, seaweeds can be cultivated and then submerged into the deep ocean or seafloor, storing some of the carbon-rich biomass. Additionally, oceans can be 'fertilized' by introducing nutrients like iron to promote the growth of phytoplankton, which can absorb carbon dioxide, convert it into biomass, and aid in carbon sequestration. Another approach involves 'artificial upwelling' by bringing nutrient-rich water from deeper levels to the surface, without adding new nutrients, to stimulate the growth of oceanic plant organisms.

According to the WRI report, there are alternative methods, known as 'abiotic' methods, that utilize the physical or chemical properties of the ocean to remove carbon dioxide from the atmosphere. These methods do not rely on marine organisms to sequester carbon. One such method involves increasing the alkalinity of the oceans by introducing specific minerals that aid in the dissolution of more carbon dioxide in seawater, allowing for its storage. Another potential approach is the use of electrochemical techniques that utilize electricity to enhance alkalinity or directly extract carbon dioxide from seawater, storing it on land.

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However, the report also highlights a cautionary note, stating that most ocean carbon removal approaches are still in the early stages of development and have undergone limited or no field testing. The effectiveness of these approaches in removing carbon, their scalability and adaptability to different locations, the duration of carbon sequestration, and the potential impacts on ocean ecosystems and the livelihoods of those dependent on them remain uncertain.

The banner image depicts the Bay of Bengal and the Indian Ocean, which have the potential to serve as storage sinks for significant amounts of carbon dioxide in the form of gas hydrates.