Carbon sequestration is a natural process of storing carbon in a carbon pool. It plays a crucial role in effectively managing the global carbon cycle and limiting climate change by reducing the amount of carbon dioxide in the atmosphere. There are two main types of carbon sequestration: biologic (also called biosequestration) and geologic.
Biologic carbon sequestration is a naturally occurring process as part of the carbon cycle. Humans can enhance it through deliberate actions and use of technology. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These processes can be accelerated for example through changes in land use and agricultural practices, called carbon farming. Artificial processes have also been devised to produce similar effects. This approach is called carbon capture and storage. It involves using technology to capture and sequester (store) that is produced from human activities underground or under the sea bed.
Plants absorb carbon dioxide from the air as they grow, and bind it into biomass. However, biological stores (such as forests and kelp beds) may be temporary carbon sinks, as long-term sequestration cannot be guaranteed. Wildfires, disease, economic pressures, and changing political priorities may release the sequestered carbon back into the atmosphere.
Carbon dioxide that has been removed from the atmosphere can also be stored in the Earth's crust by injecting it underground, or in the form of insoluble carbonate salts. The latter process is called mineral sequestration. These methods are considered non-volatile because they not only remove carbon dioxide from the atmosphere but also sequester it indefinitely. This means the carbon is "locked away" for thousands to millions of years.
To enhance carbon sequestration processes in oceans the following chemical or physical technologies have been proposed: ocean fertilization, artificial upwelling, basalt storage, mineralization, deep-sea sediments, and adding bases to neutralize acids. However, none have achieved large scale application so far. Large-scale seaweed farming on the other hand is a biological process and could sequester significant amounts of carbon. The potential growth of seaweed for carbon farming would see the harvested seaweed transported to the deep ocean for long-term burial. The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate recommends "further research attention" on seaweed farming as a mitigation tactic.
Terminology
The term carbon sequestration has diverse meanings in the literature and media. The IPCC Sixth Assessment Report defines carbon sequestration as "The process of storing carbon in a carbon pool".IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, US, pp. 2215–2256 Subsequently, a pool is defined as "a reservoir in the Earth system where elements, such as carbon and nitrogen, reside in various chemical forms for a period of time".
The United States Geological Survey (USGS) defines carbon sequestration as follows: "Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide." Because the wording in this definition makes it very similar to the definition of carbon capture and storage (CCS), carbon sequestration is sometimes confounded with CCS (the IPCC defines CCS as "a process in which a relatively pure stream of carbon dioxide (CO2) from industrial sources is separated, treated and transported to a long-term storage location").
Roles
In nature Carbon sequestration is part of the natural carbon cycle by which carbon is exchanged among the biosphere, pedosphere (soil), geosphere, hydrosphere, and atmosphere of Earth. Carbon dioxide is naturally captured from the atmosphere through biological, chemical, or physical processes, and stored in long-term reservoirs.
Plants absorb carbon dioxide from the air as they grow, and bind it into biomass. However, biological stores (such as forests and kelp beds) are considered volatile carbon sinks as long-term sequestration cannot be guaranteed. Events such as wildfires or disease, economic pressures, and changing political priorities can result in the sequestered carbon being released back into the atmosphere.
In climate change mitigation and policies
Carbon sequestration, which acts as a carbon sink, helps to mitigate climate change and thus reduce harmful effects of climate change. It helps to slow the atmospheric and marine accumulation of greenhouse gases, which is mainly carbon dioxide released by burning fossil fuels.
Carbon sequestration for climate change mitigation can involve either enhancing natural carbon sinks or employing technological methods to capture and store carbon.
Within the carbon capture and storage approaches, carbon sequestration refers to the storage component. Artificial carbon storage technologies can be applied, such as gaseous storage in deep geological formations (including saline formations and exhausted gas fields), and solid storage by reaction of CO2 with metal oxides to produce stable carbonates.
For carbon to be sequestered artificially—that is, outside the natural processes of the carbon cycle—it must first be captured, or its release into the atmosphere must be significantly delayed or prevented. This can be achieved by incorporating carbon-rich materials into long-lasting applications, such as construction, thereby avoiding release through processes like combustion or decay. Thereafter it can be passively stored or remain productively utilized over time in a variety of ways. For instance, upon harvesting, wood (as a carbon-rich material) can be incorporated into construction or a range of other durable products, thus sequestering its carbon over years or even centuries. In industrial production, engineers typically capture carbon dioxide from emissions from power plants or factories.
For example, in the United States, the Executive Order 13990 (officially titled "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis") passed in 2021 and revoked January 2025, included several mentions of carbon sequestration via conservation and restoration of carbon sink ecosystems, such as wetlands and forests. The document emphasized the importance of farmers, landowners, and coastal communities in carbon sequestration. It directed the Treasury Department to promote conservation of carbon sinks through market based mechanisms.
Noting that the planet's carbon sequestration capacity is not unlimited, a 2025 study concluded that fully using Earth's geologic storage capacity would help limit global warming by only .
Biological carbon sequestration on land Biological carbon sequestration (also called biosequestration) is the capture and storage of the atmospheric greenhouse gas carbon dioxide by continual and enhanced biological processes. This form of carbon sequestration occurs through increased rates of photosynthesis via land-use practices such as reforestation and sustainable forest management. Land-use changes that enhance natural carbon capture have the potential to capture and store large amounts of carbon dioxide each year. These include the conservation, management, and restoration of ecosystems such as forests, peatlands, wetlands, and grasslands, in addition to carbon sequestration methods in agriculture.* Methods and practices exist to enhance soil carbon sequestration in both agriculture and forestry.
Forestry
Forests are an important part of the global carbon cycle because trees and plants absorb carbon dioxide through photosynthesis. Therefore, they play an important role in climate change mitigation.IPCC (2022) Summary for policy makers in Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA By removing the greenhouse gas CO2 from the air, forests function as terrestrial carbon sinks, meaning they store large amounts of carbon in the form of biomass, encompassing roots, stems, branches, and leaves. By doing so, forests sequester approximately 25% of human carbon emissions annually, playing a critical role in Earth's climate. Throughout their lifespan, trees continue to sequester carbon, storing atmospheric CO2 long-term.Sedjo, R., & Sohngen, B. (2012). Carbon sequestration in forests and soils. Annu. Rev. Resour. Econ., 4(1), 127-144. Sustainable forest management, afforestation, reforestation are therefore important contributions to climate change mitigation.
An important consideration in such efforts is that forests can turn from sinks to carbon sources. In 2019 forests took up a third less carbon than they did in the 1990s, due to higher temperatures, droughts and deforestation. National-scale forest inventory data also shows trends from 1999 to 2020 that some forests were already approaching climate thresholds shifting them from carbon sinks to carbon sources. The typical tropical forest may become a carbon source by the 2060s.
Researchers have found that, in terms of environmental services, it is better to avoid deforestation than to allow for deforestation to subsequently reforest, as the latter leads to irreversible effects in terms of biodiversity loss and soil degradation. Furthermore, the probability that legacy carbon will be released from soil is higher in a younger boreal forest. In particular, boreal forests have been noted to support the growth of Armillaria (honey fungus), which is a root pathogen that breaks down compounds necessary for wood integrity, increasing the likelihood of carbon release. Global greenhouse gas emissions caused by damage to tropical rainforests may have been substantially underestimated until around 2019. Additionally, the effects of afforestation and reforestation will be farther in the future than keeping existing forests intact. It takes much longer − several decades − for the benefits for global warming to manifest to the same carbon sequestration benefits from mature trees in tropical forests and hence from limiting deforestation. Therefore, scientists consider "the protection and recovery of carbon-rich and long-lived ecosystems, especially natural forests" to be "the major climate solution".