Biological Carbon Sequestration

Simple Summary

Biological carbon sequestration 1 is a way to store carbon dioxide(CO2) in living organisms and ecosystems. Carbon dioxide is a greenhouse gas, which causes a warming effect on our planet. Plants take in CO2 from the atmosphere by photosynthesis and convert it into food and biomass. Microorganisms, such as fungi, use different methods of absorbing and using carbon dioxide. Utilizing biological systems to reduce CO2 will help reduce climate change in addition to improving soil health and crop production. However, it is limited by land availability, cost, and more.

1. Sequestration means to capture or store in this case. In a legal setting, sequestration means to hold someone’s assets until they pay off a debt.

   
   

What is carbon sequestration?

Carbon sequestration refers to the capturing of carbon dioxide in liquid and solid forms. Carbon dioxide levels in the atmosphere have increased by more than 85 parts per million, more than 20%, since 1979. This accounts for about 81% of the radiative forcing(warming effect) Earth is experiencing today (NOAA, 2025). Human industrial activity, specifically the burning of fossil fuels, releases otherwise controlled carbon dioxide into the air. It is clear that CO2 levels need to be controlled. Carbon sequestration is a potential way to do so as it “traps” CO2 in a nongaseous form, preventing it from remaining in the atmosphere and exacerbating the greenhouse effect. Doing so promotes carbon sinks, which is anything that absorbs more carbon than it releases. 

There are 3 main types of carbon sequestration: biological, geological, and technological(UC Davis, 2022). Biological carbon sequestration uses vegetation, soil, the oceans, and other organisms to store carbon naturally. Geological carbon capture involves pressuring carbon dioxide into a liquid form and injecting it into porous rock. Finally, technological methods, which are human invented in contrast to the natural abilities of organisms and geology, include incorporating carbon dioxide in graphene, using advanced technology in direct air capture, and engineering new molecules that can filter CO2. The next sections will explore using biological systems as carbon stores in more depth.

Mechanisms of Biological Carbon Sequestration

Photosynthetic pathways are the most common way organisms use carbon dioxide to create biomass or energy(Gayathri, 2021). Plants, algae, and some bacteria have evolved the ability to create energy, in the form of glucose, from light energy, water, and carbon dioxide. During the Calvin Cycle of photosynthesis, carbon dioxide is “fixed”, or converted, into a usable compound. It goes through a series of steps until becoming the higher energy molecule, glucose. In addition to being essential in nourishing life on Earth, photosynthesis is the largest natural absorber of CO2 from the atmosphere. Earth’s forests remove around 16 million tons of carbon dioxide per year(Harris, 2021). It is essential that forests are protected so they can continue to mitigate our carbon dioxide emissions.

We can capitalize on plants as biological carbon sinks in a few different ways. Reforestation efforts, such as ones in the Amazon Rainforest in Brazil and the Mirema Forest in Kenya, plant more trees that can absorb more carbon dioxide. Implementing certain protocols, such as prescribed burning 2 and selective logging 3, will sustain forest health(Davis, 2024). Another possible method is revitalizing grasslands. Grasses contain most of their carbon content in their roots and soil, meaning that fires will not release stored CO2(Kerlin, 2018). Basically, promoting plant life will promote carbon capture.

To expand on soil’s potential, farmers can use management techniques that increase the amount of carbon their soil can absorb. Carbon dioxide taken in by photosynthesis is most known for being converted to biomass and energy, but some of it ends up in the soil. Planting high residue 4 and cover crops 5, adding compost and manure, and using biochar 6 are ways to increase soil’s carbon capture abilities(Paustian, 2019). Soil carbon sequestration is notably enhanced by mycorrhizal fungi(Treseder, 2013). These are soil organisms that are allocated a portion of carbon plants capture. Mycorrhizal fungi then use their allocation to create hyphae, thread-like filaments that branch into the soil. When the fungi die, the soil can contain its carbon for years. According to a 2023 study from Current Biology, an estimated 13 million tons of CO2 is sequestered due to this fungal species per year. Avoiding chemical fertilizers and planting a diverse array of crops increase fungal health and, therefore, their ability to reduce carbon dioxide levels(Ellerbeck, 2022).

Carbon sequestration also occurs in the oceans, which absorbs ~30% of human CO2 emissions(Gruber, 2019). There are abiotic and biotic methods of oceanic carbon capture, this paragraph discusses the biotic. On land, carbon basically cycles from the atmosphere to producers to consumers to decomposers back into the atmosphere or into the soil, where it is mostly locked until humans mine and burn it for energy. In the ocean, carbon is taken from the atmosphere by photosynthetic phytoplankton and algae which are consumed; then, when an organism dies, most of its matter is decomposed, allowing some carbon dioxide to return to the atmosphere, but the rest can sink and be stored within the deep ocean. Ocean fertilization, i.e., adding nutrients such as iron, can increase phytoplankton growth, allowing for more CO2 absorption(Lebling, 2022). Adding highly efficient algal species, such as Botryococcus braunii and Scenedesmus obliquus, will maximize carbon capture and biomass production(Gayathri, 2021).

2. Prescribed burning is the intentional introduction of small fires to forests that removes excess dead bush and tree, vegetation, and invasive species that prevents bigger wildfires and promotes ecosystem health.

3. Selective logging is the removal of specific trees based on certain selection criteria rather than cutting down large swaths of trees without thought

4. High residue crops leave behind significant amounts of plant material after being harvested

5. Cover crops, such as cereals and legumes, are grown to cover soil which increase the soil’s carbon content

6. Biochar is a carbon-rich solid created using fire

Advantages, Limitations, and Risks

Each way of biological carbon sequestration has its advantages, limitations, and risks.

Planting trees and grasses does not require excessive energy input, making it sustainable. Reforestation and preservation efforts may also create jobs. Limitations to planting efforts include land availability and cost. Furthermore, in some cases, planting an enormous number of new trees could do more harm than good. At the poles, added flora could inhibit the regions’ ability to reflect light(Gramling, 2021). If new trees are planted with no regard to native species, biodiversity loss could accelerate. Maintaining existing forest and grassland ecosystems will preserve biodiversity and is more economic, as finding new land and plants will not be an issue. Another risk is the possibility of carbon leakage. Wildfires and deforestation release CO2 stored in trees, and if we try to store additional carbon in trees without addressing these issues, planting efforts would be in vain(Kerlin, 2018). Balancing tree planting with grassland vitalization will help this as carbon in grasslands is mostly stored underground and will not be released by wildfires.

Soil and fungal carbon capture ventures have the advantage of working in existing ecosystems. That requires a shorter timeframe than other efforts. Also, increasing carbon levels in soil improves soil health, which improves crop yield(Paustian, 2019). Existing practices used by green-conscious farmers can become more widely adopted to promote soil’s carbon absorption abilities. Promoting fungal health aids in soil structure, which increases water retention, and nutrient cycling to the plants(Emilia Hannula, 2022). Both of these methods are limited by the willingness of farmers to implement them. They present costs, so we need to incentivize them in some way to persuade farmers.

Oceanic carbon sequestration has an enormous scope simply due to the size of our oceans. Harnessing it has the potential to offset our carbon emissions greatly. However, there are a number of risks. Carbon dioxide becomes acidic when dissolved in water, so intensifies the acidification of bodies of water. Trying to use the ocean as a bigger carbon sink could harm marine ecosystems and eventually inhibit its ability to absorb carbon due to the associated acidification(Lebling, 2022). Large scale efforts in this area are also limited by technological feasibility and costs.

Conclusion

It is necessary to address the social and political contexts of carbon sequestration. Tree planting legislation has historically been widely supported and bipartisan, but has flaws. It was touted as a major solution to our climate crisis, but this was exaggerated and didn’t address issues like biodiversity. Trees cannot fix everything. Similarly, many fossil fuel companies have invested in carbon capture technologies as an excuse to continue mining(EarthJustice, 2023). While carbon sequestration technology is positive in itself, it distracts from achieving a zero emissions economy. However, these concerns pale in comparison to the potential consequences of the actions taken by the Trump administration. The declaration of a “national energy emergency” that promotes oil and gas use, removing electric vehicle goals, and budget cuts to climate research will do extensive harm to environmental efforts. Carbon capture research and implementation is just one of many environmental initiatives on the chopping block right now. 

References

1. Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm Review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885

2. Earthjustice. (2023, September 19). Carbon capture: The fossil fuel industry’s false climate solution. https://earthjustice.org/article/carbon-capture-the-fossil-fuel-industrys-false-climate-solution

3. Ellerbeck, S. (2022, July 4). Is fungi the most underused resource in the fight against climate change?. World Economic Forum. https://www.weforum.org/stories/2022/07/fungi-forests-carbon-climate/

4. Emilia Hannula, S., & Morriën, E. (2022). Will fungi solve the carbon dilemma? Geoderma, 413, 115767. https://doi.org/10.1016/j.geoderma.2022.115767

5. Gayathri, R., Mahboob, S., Govindarajan, M., Al-Ghanim, K. A., Ahmed, Z., Al-Mulhm, N., Vodovnik, M., & Vijayalakshmi, S. (2021). A review on Biological Carbon Sequestration: A sustainable solution for a cleaner air environment, less pollution and Lower Health Risks. Journal of King Saud University - Science, 33(2), 101282. https://doi.org/10.1016/j.jksus.2020.101282

6. Gramling, C. (2021, July 14). Why planting tons of trees isn’t enough to solve climate change. Science News. https://www.sciencenews.org/article/planting-trees-climate-change-carbon-capture-deforestation 

7. Gruber, N., Clement, D., Carter, B. R., Feely, R. A., van Heuven, S., Hoppema, M., Ishii, M., Key, R. M., Kozyr, A., Lauvset, S. K., Lo Monaco, C., Mathis, J. T., Murata, A., Olsen, A., Perez, F. F., Sabine, C. L., Tanhua, T., & Wanninkhof, R. (2019). The oceanic sink for anthropogenic co2 from 1994 to 2007. Science, 363(6432), 1193–1199. https://doi.org/10.1126/science.aau5153 

8. Harris, N. L., Gibbs, D. A., Baccini, A., Birdsey, R. A., de Bruin, S., Farina, M., Fatoyinbo, L., Hansen, M. C., Herold, M., Houghton, R. A., Potapov, P. V., Suarez, D. R., Roman-Cuesta, R. M., Saatchi, S. S., Slay, C. M., Turubanova, S. A., & Tyukavina, A. (2021). Global maps of twenty-first century forest carbon fluxes. Nature Climate Change, 11(3), 234–240. https://doi.org/10.1038/s41558-020-00976-6

9. Hawkins, H.-J., Cargill, R. I. M., Van Nuland, M. E., Hagen, S. C., Field, K. J., Sheldrake, M., Soudzilovskaia, N. A., & Kiers, E. T. (2023b). Mycorrhizal mycelium as a global carbon pool. Current Biology, 33(11). https://doi.org/10.1016/j.cub.2023.02.027

10. Kerlin, K. E. (2018, July 9). Grasslands more reliable carbon sink than trees. UC Davis. https://climatechange.ucdavis.edu/news/grasslands-more-reliable-carbon-sink-than-trees/

11. Lan, X., Tans, P. and K.W. Thoning: Trends in globally-averaged CO2 determined from NOAA Global Monitoring Laboratory measurements. Version Friday, 14-Mar-2025 

12. 11:33:44 MDT https://doi.org/10.15138/9N0H-ZH07

13. Lebling, K., Northrop, E., & McCormick, C. (2022, November 15). Ocean-based carbon dioxide removal: 6 key questions, answered. World Resources Institute. https://www.wri.org/insights/ocean-based-carbon-dioxide-removal

14. Paustian, K., Larson, E., Kent, J., Marx, E., & Swan, A. (2019). Soil C sequestration as a biological negative emission strategy. Frontiers in Climate, 1. https://doi.org/10.3389/fclim.2019.00008 

15. Treseder, K. K., & Holden, S. R. (2013). Fungal carbon sequestration. Science, 339(6127), 1528–1529. https://doi.org/10.1126/science.1236338

16. UC Davis. (2022, February 1). Carbon sequestration. https://www.ucdavis.edu/climate/definitions/carbon-sequestration

17. Walling, M. (2025, January 27). What to know about Trump’s first executive actions on climate and environment. AP News. https://apnews.com/article/trump-executive-orders-climate-change-environmental-policy-e4fb2b2495c0bcf880fab46605936b09