What’s a carbon sink and what is its environmental impact?

12 June 2023 | Protect the environment

A carbon storage is a natural or artificial process allowing the storage of CO2. It basically allows to limitate and retard global warming, it has a real environmental impact.

But what is it precisely ?

Why store emissions of CO2 ?

CO2 is naturally present in the atmosphere and is one of the greenhouse gases responsible for global warming. 

For this reason, the last report of GIEC, asks for a fast establishment of solutions to reduce greenhouse gases emissions and thus limit global warming to 1,5°C by 2050. 

At this moment, carbon sinks intervene. Indeed, they maintain a certain balance and allow to store for centuries tons of CO2. Thus preventing this last to spread out in the atmosphere. 

What’s a carbon storage ? 

A carbon storage is a system allowing to limit the concentration of CO2 in the atmosphere to store them sustainably on or under earth. These containers catch a part of our carbon emissions thanks to : 

  • the mechanism of photosynthesis, which transforms the CO2 in oxygen. 
  • physical and chemistry mechanisms, which delete the CO2 or that convert it into calcium carbonate, entraining it into deep waters.   

How does the carbon sink work ? 

Natural carbon sinks work thanks to photosynthesis. That uses solar energy to fix the CO2 in the form of organic matter. Afterwards, this matter will progressively transform itself into sedimentary rocks, in which the carbon will stay trapped. 

The preservation of carbon sinks is primordial because some human activities such as deforestation or artificialization of grounds reduce this store of organic matter. However when these places are destroyed, the store of CO2 trapped is freed in the atmosphere. 

There also exist artificial carbon sinks, which are completely made by humans. For the past few years, we have started to improve natural mechanisms by using geologic sequestration that allows to inject directly underground carbon dioxide. 

What are the main natural carbon sinks ?

There are different carbon sinks, the most important are oceans, forests/soils, and peat bogs. 

The oceans : 

They absorb 3.2 billions of tons of carbon per year. This represents 50% of anthropics emissions (generated by humans). These are the most important carbon sinks, thanks to planktons, fishes and corals. 

  • Marine organisms use the carbon to make their shell or their skeletons. 
  • The carbon is dissolved in cold waters of the seafloor and is then stored for hundred years. 
  • 60% of CO2 catched stays on the ground, the plankton, thanks to the sunlight, transforms CO2 into organic matter. 

Nowadays, oceans are a carbon sinkl menaced by global warming. Waters become more acidic, thus causing the bleaching of corals so the reduction of the capacity of the carbon storage. 

Forests and soils : 

Trees produce oxygen, by conserving a part of carbon dioxide that they absorb thanks to the process of photosynthesis. They are very important in CO2 storage. Indeed, a big part of CO2 catched is then stored into woods, roots and this humus generated by the decomposition of leaves and branches fallen on ground. We estimate that a mature tree catches about 30kg of CO2 every year, but that more of the half of stored carbon in the woods is in the ground, and not in the visible part of the tree. 

These ecosystems are fragile yet. Jeopardized by the forest exploitation, the exploitation of natural resources, industrialization, urban development, agricole development, these spaces know reductions of surfaces in many zones of the globe. 

Furthermore, the effects of global warming and of its intenses periods cause more and more important fires ( Australia, USA and Canada, Europe). This is causing an important release of CO2 stored for centuries. 

The peat bogs : 

They store twice as much carbon as all forests. That is 25% of the organic carbon stored in soils. However, they only represent 3% of land area and are endangered. Peat bogs have contributed significantly to the regulation of atmospheric CO2. The organic matter accumulated, the peat, contains about 50% of carbon. That is given to peat bogs a global capacity of a very important storage. 

This ecosystem nevertheless remains fragile and jeopardized. In fact the preservation of peat bogs is crucial because they have the capacity of storing more carbon than the largest forests.

What is the environmental impact of carbon storages ?

The natural carbon storages have a good environmental impact. In a natural way, the atmosphere exchanges carbon for billions of years with other spheres, into wells where natural carbon is stored. 

However, the dewatering of different biomes (groups of ecosystems that characterize the vegetation and animal species) including the boreal and tropical rainforest. But also the modification of ocean currents or still the ocean becoming more acidic, can at the end harm natural carbon storages. And thus to make that these wells can’t capture CO2 but on the contrary produce some. 

Artificial carbon storages, what is it ? 

Humans are currently developing technologies of artificial carbon storages. Here we are focusing on the catchment of CO2 : it is a matter of trapping it artificially in geological formations, in oceans but also in old wells of oil. 

These capture technologies and of CO2 storage consist to recover the greenhouse gas during its production (as an example in its petrochemicals proceeds) but also in the atmosphere and then store it in the ground, or use it for industrial purposes. The catchment of CO2 is a very expensive technologie and energy consumer. This technique is not a solution to reduce carbon emissions. However, it favors their catchment to avoid their dispersion in the atmosphere. 

How does the catchment and CO2 burial work ? 

The purpose is to capture the carbon emitted by human activities in the atmosphere to reinject it and store it underground. 

Some large companies and industrial groups wish to catch and store the carbon of their activity by burying it in natural pockets underground. Indeed, current technologies can capture about 90% of emitted emissions by some industrial process, petrochemicals by example. According to the report of the Agence Internationale de l’Energie, the system could contribute to reducing about 15% of global emissions of fossil energies by 2060. 

The catchment of CO2 is however a high cost technologie and consumer of energy. 

Installations of catchment are at the moment only compatible with the industrial sector. Indeed, the majority of existing facilities of catchment of CO2 reuse it to improve the oil recovery, by re-injecting it into wells to increase the pressure and make its extraction easier. Projects are in development, and mobilize investments that are up to many billions of euros everywhere in the world. 


The natural carbon storages are part, for hundreds of billions of years, of the balance and the revolution of the concentration of CO2 in the earth’s atmosphere. Their development has captured and fixed billions of tons of CO2 in soils and in oceans. 

But the balance is nowadays modified by human activities : increase of carbon emissions, destruction of existing natural carbon storages or of their ecosystem allowing their regeneration, ocean acidification, and climatic modifications, leading to a disruption of these balances. The global consequences of these modifications could be cataclysmic, that’s why it’s important to promote all actions allowing to act on human carbon emissions, of which the reduction of the carbon emissions of digital technology.

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