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Carbon Sinks: Where is Carbon Stored?

Carbon is stored naturally and safely for decades to millennia in various locations, such as trees, soil, and rocks. Carbon is transferred between these so-called sinks and the atmosphere through a series of processes called the carbon cycle. These sinks are critical to keep the balance of carbon dioxide in the atmosphere, which has been upset by climate change. Utilising these natural storage locations is an essential element of carbon removal solutions.

What is a carbon sink?

A carbon sink is a natural reservoir that absorbs more carbon than it releases, playing a crucial role in maintaining manageable levels of CO2 in the atmosphere. These different locations vary in how long carbon is stored, from years to millennia, called durability or permanence. Each sink has a vital function in the cycle of carbon.

Klimate works with nine different carbon removal methods (and counting) which sequester and store carbon in different sinks.

Waves crashing on rocks
Illustration of Coastal Blue Carbon

Where is carbon stored naturally?

Natural carbon sinks, such as forests, oceans, and soil, absorb a significant amount of carbon from the atmosphere—about 50% of all human-induced emissions. The world's forests alone absorb 2.6 billion tonnes of CO2 each year.

How are natural sinks used in carbon dioxide removal?

All methods of carbon removal utilise natural carbon sinks in some way. Even engineered methods utilise geological storage systems. The table below describes several important carbon sinks and how they are utilised by removal methods.

Types of carbon sink Land (forests, grasslands & soils ) Oceans Geological formations
How they store carbon Tree and other plants take up carbon through photosynthesis, storing it in their biomass.

Once plants die, this carbon is stored in soil via decompisition.

Carbon can also be stored long-term in timber used for building.

Phytoplankton and other forms of marine life take up carbon via photosynthesis, similarly to plants.

When they die, this carbon sinks to the ocean floor, where it is stored for the long term in seabed sediments.

Geological formations like volcanic rocks and underground saline formations are also key carbon storage sites.

Engineered carbon removal methods are able to pressurise CO2 into liquid form, which can then be injected into basins of porous rock deep underground.

Permanence range Decades - centures

10s-100s of years

Centuries - millenia

100s-1000s of years

Millenia - epochs
>10,000 years
Klimate's methods Forestation, soil sequestration, biochar Ocean blue carbon, coastal blue carbon, enhanced weathering Bio-oil, bio-energy with carbon capture and storage (BECCS), direct air capture (DACCS)

Challenges of emissions and land use change

Rising greenhouse gas emissions are upsetting the balance of the carbon cycle, leading to a situation where carbon sinks are unable to absorb all the carbon being released.

Simultaneously, more and more land is being converted for urbanisation and agriculture. This often involves disturbances, like deforestation, that release carbon already stored in the land, while preventing it from sequestering any further emissions. 

This poses a significant challenge, as the importance of carbon sinks in tackling climate change has never been greater.

Currently the EU's land use sector is actually a net carbon sink, meaning it absorbs more carbon that it releases. On a global scale, however, the opposite is happening.

Which carbon sinks are most important for CO2 removal efforts?

There is no doubt that preserving and expanding natural carbon sinks should be a priority. They have strong co-benefits for biodiversity and are deployable now, creating rapid carbon uptake and safe storage in the short term. At the same time, geological carbon sinks which can be accessed through engineered solutions are highly permanent and hold huge potential to accelerate carbon removal. 

Waves crashing on rocks

These solutions are essential to mitigate carbon emissions and ensure the stability of the global climate. At Klimate, we aim to drive balanced investments into nature-based solutions alongside technology-driven removals that demonstrate high integrity and scaling potential.

Further reading

  • Luhtaniemi, M.: Forest carbon sinks under pressure. FLUXES (The European Greenhouse Gases Bulletin) Vol. 2., 2023.
  • McKinley, G. A., Fay, A. R., Eddebbar, Y. A., Gloege, L., & Lovenduski, N. S. (2020). External forcing explains recent decadal variability of the ocean carbon sink. AGU Advances, 1, e2019AV000149. https://doi.org/10.1029/2019AV000149
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Talk to a carbon removal strategist

Finding the right way to remove your CO₂ emissions can seem overwhelming. Luckily, we are always here to help. You can book a meeting to walk through how our solution might fit your needs, or simply send us a message.

Book a demo

Talk to a carbon removal strategist

Finding the right way to remove your CO2 emissions can seem overwhelming. Luckily, we are always here to help. You can book a meeting to walk through how our solution might fit your needs, or simply send us a message.