Blue Vaults of Nature

In the past few articles we have discussed various ways of removing carbon dioxide from the air, such as Carbon Capture and Sequestration (CCS), Direct Air Capture (DAC), Enhanced Rock Weathering (ERW) and biochar. Marshlands, mangroves and sea grasses provide a natural mechanism for removing carbon dioxide from the air (These are also referred to as Blue Carbon). They also provide natural and positive externalities such as increased biodiversity in the coastal and marine ecosystem, and a natural bulwark against cyclones and storms. Mangroves are, however, under threat and are fast disappearing from various parts of the world and need to be protected. In a previous article on blue carbon, we had looked at it from the viewpoint of Adaptation. In this article, we will focus on the carbon dioxide removal aspect of Blue Carbon.

The Importance of Blue Carbon in CDR

In the previous article, we had defined blue carbon as any carbon stored and sequestered by the ocean. In coastal areas, blue carbon is basically the carbon stored in vegetation such as mangroves, sea grasses and sea marshes and the deep soils that remain under water.

According to the World Resources Institute, oceans already absorb 30 percent of all carbon dioxide in the air and 90 per cent of excess heat. In all, the oceans hold 42 times more carbon than the atmosphere. This has put the oceans under extreme stress, leading to excess warming, acidification and loss in oxygen, thereby endangering the marine ecosystems. To address this, ocean CDR has been suggested as a solution, which basically aims to undertake blue carbon restoration. This can happen by increasing the capacity of the ocean to store carbon through an accelerated process of photosynthesis. This, in turn, is done with the help of improving the coastal and marine ecosystem consisting of mangroves, phytoplankton, seaweed and sea grasses.

The National Renewable Energy Laboratory under the Department of Energy of the US has listed the following ways to enhance the ocean’s capacity in CDR:

• Enhanced ocean alkalinity by physical or abiotic means such as adding chemicals. Electrochemical techniques, which use electricity to mimic alkalinity can also be used to extract carbon dioxide and store it on land.
• Algae, seaweed and phytoplankton cultivation can be undertaken by adding nutrients to the ocean. Seaweed and phytoplankton can be cultivated and large chunks of these can be stored on the ocean floor in the form of biomass.
•  Mangrove restoration can lead to greater amounts of carbon dioxide stored in their stems and roots. The added benefits include enhancement of biodiversity and increased productivity of marine life.

In an article titled Aboveground Carbon Stocks in Rapidly Expanding Mangroves in New Zealand, published in the journal Estuaries and Coasts in April, 2020, Suyadi, Jay Gao, Carolyn J Lundquist and Luitgard Schwendenmann noted that mangroves, tidal marshes and seagrasses are important ecosystems to sequester and store carbon. Citing other research, they state that “blue carbon” is a far more efficient way to capture carbon. They point out that as compared with terrestrial ecosystems, blue carbon ecosystems have a greater capacity to store large amounts of carbon belowground, partly due to the trapping and accretion of sediment associated with organic carbon and reduced organic matter decomposition because of low oxygen availability in sediments. Their own research in the paper also concludes that the aboveground mangroves have grown in the Auckland area of New Zealand, and have a large capacity to capture carbon.

Conclusion

Blue carbon has a high carbon sequestration capacity, including that of capturing carbon dioxide. Given that the marine and coastal ecosystems have come under threat, particularly due to excessive exploitation in the Exclusive Economic Zones of various countries, it has become all the more important to protect and restore these ecosystems. In addition, associated steps such as algae and seaweed farming on the seafloor and increasing ocean alkalinity by chemical and physical means are also important. It is also encouraging that measuring the carbon stored in these ecosystems is now possible with new instruments and techniques. Preserving and restoring the blue carbon ecosystems continue to be important parts of the journey to net zero all over the world.

The writer is Additional Chief Secretary, Department of Cooperation, Government of West Bengal. Views expressed are personal