The ocean stores about 93% of the carbon dioxide on the earth.

And more than 30% is removed every year.

Carbon dioxide discharged into the atmosphere

Several ways of 0 1 ocean carbon sink

According to the requirements of China's carbon neutrality goal, we can achieve emission reduction and increase foreign exchange without reducing production. The ocean with an average water depth of 4000 meters and covering 70% of the earth has become a key area for exploring "negative emissions".

At present, the main known marine carbon sequestration mechanisms include solubility pump, carbonate pump (CCP) and biological pump (BCP).

Solubility pump uses the partial pressure of carbon dioxide in the atmosphere higher than that in the ocean to make carbon dioxide dissolve in seawater and be "dragged" into the deep sea under the gravity of high-density seawater. It seems perfect, but in the process of carbon dioxide dissolving in seawater, it is easy to cause ocean acidification, destroy the marine environment and marine biodiversity, and belongs to the type of "killing one thousand enemies and losing eight hundred". In addition, the process is difficult to control, so it is not the object of scientific research and development.

Carbonate pumps store carbon dioxide on the seabed through carbonate deposition. Because of its chemical process, it releases the same amount of carbon dioxide, so it is also called reverse pumping, which belongs to "good-hearted" players. But scientists may take measures to adjust the boundary conditions and turn this "reverse pump" into a "forward pump".

Biological carbon pump is a process that granular organic carbon is formed through biological processes such as organic matter production, consumption and transportation, and then migrated and buried from the ocean surface to the deep sea or even the seabed under the action of gravity. In this process, from the photosynthesis of phytoplankton, organic carbon gradually shifted from primary producers to high trophic level along the food chain, and deposited granular organic carbon, and some carbon was sealed in the ocean for a long time.

The scientific community spoke highly of the carbon sequestration and storage of bio-pumps, and believed that without bio-pumps, the carbon dioxide content in the atmosphere would be 200ppmv higher than it is now.

Although the biological pump is good, the carbon burying efficiency is too low. It is estimated that the amount of carbon dioxide transported and buried by the bio-pump to the seabed is close to 65,438+0% of the marine primary productivity, and most of the particulate organic carbon is "dumped" in the sediment. How to use it efficiently has become the goal pursued by scientists.

02 miniature biological carbon pump, wax sealed "meatballs"

After years of systematic research and scientific experiments, scientists in China have gradually realized the important role of microorganisms in marine ecosystems in the formation of marine carbon pools. Jiao Nianzhi, an academician of China Academy of Sciences, put forward a new ocean carbon storage mechanism-miniature biochar pump, which led the international frontier development trend in this field.

95% of the organic carbon in the ocean is dissolved, of which 95% is inert organic dissolved carbon, which can be preserved in the ocean for about 5000 years.

Micro-biological carbon pump absorbs active organic carbon through physiological and ecological activities such as microorganisms and plankton in the ocean, and then converts active organic carbon into inert organic carbon and stores it in seawater. Inert organic carbon is not easily degraded, so it can accumulate to form a huge carbon pool.

It is estimated that the amount of inert organic carbon in the ocean is equivalent to the amount of atmospheric carbon sink. Therefore, marine carbon storage has great potential and plays an important role in regulating climate change.

Theoretically, all kinds of plankton and microorganisms on the ocean surface absorb carbon dioxide in the atmosphere, become granular organic carbon, and then sink into the seabed under the action of gravity to achieve the purpose of carbon fixation. However, the actual situation is that in the process of settling to the seabed for thousands of meters, particulate organic carbon is degraded very badly, which can be said to be exponential decay. The result is like a big funnel, which looks a lot, but the number that finally reaches the bottom of the sea is pitiful.

This process can also be understood as all kinds of marine life and microorganisms are like delicious meatballs. After absorbing carbon dioxide to form granular organic carbon, it is "eaten" by marine microorganisms and bacteria all the way to the seabed because of its delicious taste.

This is not the result we want. However, if particulate organic carbon collides with inert organic carbon molecules in the process of sedimentation, it will be beneficial to protect particulate organic carbon. This is equivalent to wrapping a layer of wax on a delicious meatball with granular organic carbon, which makes the taste worse and the bacteria lose interest in it, so it can sink to the bottom of the sea and be preserved for a long time.

This is similar to the principle of submarine oil formation, and the scientific community is verifying its similarity through experiments to open up the "last mile" for marine carbon storage.

10 years ago, the concept of microbial carbon pump put forward by Jiao Nianzhi was little known, and it was approved by the scientific community at home and abroad after many large-scale ecosystem simulation experiments. Subsequently, the theory was written into the IPCC report. American scientists say that although the formation of this huge inert organic carbon pool is still a mystery, its role in regulating climate change is enormous. Moreover, in the history of the earth, the inert organic carbon pool was at least 500 times larger than it is now.

Nowadays, scientists are still studying how to adjust the boundary conditions of the reaction among carbonate pump, biological pump and microbial pump in order to realize the synergy of the three pumps. By then, it is possible to realize the large-scale carbon storage phenomenon that has appeared in history.

In fact, there are indeed many examples of large-scale carbonate deposition caused by microorganisms in the history of the earth. Anaerobic and aerobic microorganisms are used as reaction media to help carbon deposition. In Britain, Beachy Point in the English Channel is a white cliff with a height of over 100 m and a length of 5 km. The white cliff of Dover is a carbonate sedimentary landscape, which is formed by very small (20 microns, or 0.02 mm) microorganisms.

How to coordinate land and sea, reduce emissions and increase foreign exchange?

As early as 10 years ago, Jiao Nianzhi also proposed a plan to reduce land fertilization and increase offshore carbon sinks.

American scientists have studied the relationship between inorganic nitrogen and organic carbon in various environments and offshore lakes and oceans. The results show that if there are too many nutrients in the environment, it is difficult to preserve organic carbon. This is the same as the microscopic observation in the laboratory.

Statistics from the National Bureau of Statistics show that in the past 50 years, the use of chemical fertilizers in China has increased by nearly 30 times, and the global use of chemical fertilizers has increased by 30%. Excessive nitrogen, phosphorus and other fertilizers enter the river and eventually flow to the ocean under the scouring of rain, which makes the coastal waters eutrophic. The excessive nutrient input from land sources and the stimulation from sea sources make the estuary with high productivity become the source of releasing carbon dioxide.

The estuary is rich in nutrients and has become a breeding ground for all kinds of bacteria. Bacteria decompose organic carbon, release carbon dioxide, and activate terrestrial organic carbon into carbon dioxide.

Jiao Nianzhi suggested that the demonstration project of microbial-driven, inorganic-organic-biological-abiotic comprehensive carbon storage should be implemented, and the mechanism of land and sea planning, emission reduction and sink increase-quantitative ecological compensation should be implemented to promote domestic circulation.

At present, the International Scientific Plan on Negative Marine Emissions (ONCE) initiated by Academician Jiao Nianzhi has received positive response from international counterparts, and scientists from 15 countries have signed up to join. Jiao Nianzhi called on China to comprehensively carry out scientific planning of marine negative emissions, release relevant research and development results in a timely manner, establish relevant methods and technical systems as soon as possible, and launch a standard system of marine carbon sinks (negative emissions) led by China through ONCE, so as to provide a Chinese plan for building a community of human destiny.