Pathways of Carbon Sequestration in Nature

Carbon sequestration in nature is the process of converting carbon dioxide into carbon to be fixed on land or in seawater through a variety of natural processes in order to mitigate global climate change and the greenhouse effect.

Carbon sequestration refers to measures to increase the carbon content of carbon pools other than the atmosphere. It includes physical carbon sequestration and biological carbon sequestration. Physical carbon sequestration is the long-term storage of carbon dioxide in mined oil and gas wells, coal seams and the deep sea. Biological sequestration is the conversion of inorganic carbon, i.e., atmospheric carbon dioxide, into organic carbon, i.e., carbohydrates, which are immobilized in the body of plants or in the soil.

There are two common methods of carbon sequestration: photosynthesis, such as various green plants and photosynthetic autotrophic microorganisms (e.g., cyanobacteria); and chemoenergetic synthesis, such as nitrifying bacteria using oxidized ammonia to synthesize organic matter. Biological carbon sequestration improves the ecosystem's ability to absorb and store carbon and reduces the concentration of carbon dioxide in the atmosphere.

On June 2, 2022, the Tarim Desert Highway "Zero Carbon Demonstration Project", China's first graded highway through the Taklamakan Desert, was officially put into operation. From now on, this highway through China's largest desert will become a zero-carbon emission highway. After the commissioning, the protective forest belt on both sides of the highway can sequester 20,000 tons of carbon annually, completely neutralizing the carbon emissions of passing vehicles.

Marine physical carbon sequestration, refers to the role of the ocean "physical pump", so that the seawater in the carbon dioxide - carbonate system to the deep sea diffusion and transfer, and ultimately the formation of calcium carbonate, deposited on the seabed, the formation of calcareous soft mud, so as to play a role in carbon sequestration. This gas exchange process at the sea-gas interface and the hydrodynamic process of carbon dioxide transport from the ocean surface to the deep sea are known as the "physical pump".

Deep-sea sequestration

Deep-sea sequestration is another effective method of carbon sequestration. Since fossil fuels, especially coal, are still the most important energy fuels in China, in order to fulfill our commitment to reduce carbon dioxide emissions and to cope with the possible international trade "carbon tariffs", one of the solutions is to look for places and methods to store large amounts of carbon dioxide for a long period of time.

Scientific research has found that in the deep ocean, carbon dioxide will form a hydride with water, forming a solid shell on the outside, which restricts carbon dioxide contact with seawater; when the depth of seawater is greater than 3,000 meters, the surface of the liquid carbon dioxide can form a stable hydride shell, which will be sufficient to deal with the most serious earthquakes or other drastic changes in the Earth's gas stored in this way.