10 Processes that Remove Carbon Dioxide From the Atmosphere
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10 Processes that Remove Carbon Dioxide From the Atmosphere

By Achraf El Madnaoui

The severity of the climate emergency begs a simple yet fundamental question: what if we could effectively remove carbon dioxide from the atmosphere? Researchers, scientists, and environmentalists alike have identified a series of concrete actions we can take to support a more sustainable, environmentally friendly global civilization. 

A large-scale carbon dioxide removal process, known otherwise as negative emissions, is a feasible and efficient way to address our damaging contributions to the changing climate. If exercised at a planetary level, this drawdown process could help reduce ocean acidification and thereby slow the rate of climate change to the point of sustainability. There are a wide range of approaches to carbon reduction—below are some of the most widely practiced approaches. 


Biochar is a type of charcoal produced by heating biomass in environments with little to no oxygen. Adding and mixing biochar into existing soil is an effective method to remove carbon dioxide from the atmosphere: as plants grow, they use photosynthesis to capture atmospheric carbon dioxide and harness it to produce additional biomass. The carbon present in this biomass subsequently gets converted into a more “stable form of biochar”. Burying this biochar enables a long storage for carbon, thereby preventing CO2 from being released into the atmosphere and negatively affecting the climate.

As such, the usage of biochar to combat climate change comes with various benefits and drawbacks. First and foremost, biochar significantly enriches soil nutrients, mainly by increasing moisture content and microbial activity. This boosts agricultural productivity, helping produce more fruits and vegetables and ensuring that developing countries are afforded a reassuring measure of food security. 

But despite improvements in soil quality, biochar does dramatically restrict the “activity of worms in soil which is essential for consistent soil productivity.” A decline in soil productivity in effect trickles down to a decrease in agricultural efficiency. And since biochar absorbs the water and nutrients necessary for growing plants, crop yield may decrease too. These negative effects can lead to soil degradation, undermining its durability against harsh climate conditions. 


Soil Carbon Sequestration

Soil carbon sequestration, also known as carbon farming, is a regenerative process used commonly among farmers to reduce and potentially reverse agricultural greenhouse gas emissions. This process involves plants capturing, or rather “sequestering,” atmospheric carbon dioxide in the soil and consequently increasing the total amount of soil carbon stocks. Increasing soil carbon is done in a variety of ways—below are some specific examples and their environmental benefits, outlined in an article published by American University:

  • Switching to low-till or no-till approaches to improve soil quality and reduce any structural disturbance
  • Applying crop residues to fields to improve soil structure and increase organic matter in the soil
  • Revising planting schedules in consideration of individual plant maturity dates and needs

Despite the clear benefits, the science is unclear on the viability of soil carbon sequestration as a climate change solution, particularly with respect to how much carbon can be stored and for how long. The difficulty in measuring carbon sequestration has raised concerns among scientists in touting the potential of this method. Soil science has evolved dramatically over the past decades, and assumptions surrounding soil carbon storage maintenance have been disputed. Specifically, there has been growing evidence to support the idea that no-till agricultural practices do not store as much carbon as initially believed. A study from MIT has pointed out that climate change has “made it more difficult for soils to naturally store carbon and that the warming of the planet could lead to devastating and widespread soil carbon losses.” This challenges the efficacy and sufficiency of carbon sequestration technologies, and that is why scientists have been exploring other means of carbon dioxide removal.


Afforestation and Reforestation

Climate change and forest ecosystems are fundamentally interconnected. As such, the effects of climate change can dramatically change “forest structure, their growth patterns, composition, productivity, and overall functioning.” Afforestation and reforestation are two nature-based solutions that serve to contribute to the sustainable development of damaged or non-existent forests. At the international level, both of these methods have been accepted as efficient mitigation strategies and have been promoted as a means to achieve carbon sequestration targets.

Afforestation and reforestation are hugely important in ensuring the protection of ecosystems by reducing their vulnerability to climate change. Increasing the number of forests means creating new resilient habitats for tolerant species and therefore enhancing biological diversity. Most importantly, new and standing forests absorb carbon dioxide. In fact, the World Resources Institute estimates that “forests absorb twice as much carbon as they emit each year.” Afforestation and reforestation can also regulate and control soil damage and degradation, reduce landslide risks, and protect coastal communities from extreme weather events.

Planting new forests, however, does limit space for critical public infrastructure and agriculture. This can negatively impact local communities who heavily rely on residential space for housing needs and agriculture for food production. In other words, while afforestation and reforestation help in managing and conserving genetic diversity, it can affect livelihood. 



Over the last decade, bioenergy usage has been sidelined in the public policy debate despite its promising climate change mitigation potential. According to IPCC assessment reports, a large-scale deployment of bioenergy in conjunction with carbon capture and storage can transform the energy system to reduce carbon emissions and facilitate a developmental transition to renewable energy. 

The benefits of bioenergy are manifold: first, it helps reduce waste by limiting the size of landfills, therefore drastically improving soil and water quality. Bioenergy also contributes hugely to a more sustainable and economically healthy future by ensuring the stability of domestic clean energy sources, lessening dependence on foreign oil, and stimulating economic growth particularly in rural areas. Specifically, bioenergy development in rural areas offers a chance to further meet agricultural needs and enhance a crumbling transportation infrastructure. This can provide a great measure of financial security by increasing household incomes. 

There are also a number of disadvantages that ought to be considered. Some have raised concerns about the potential negative effects of bioenergy on the environment. The UN Food and Agriculture Organization has noted that “an expansion in bioenergy crops might come at the expense of food production, leading to reduced food availability and higher food prices.” Additionally, the conversion of new lands to bioenergy cropping systems can lead to deforestation, which in turn can create a host of problems for indigenous people and undermine environmental sustainability initiatives.  


Direct Air Capture

A more methodical approach to climate change mitigation is direct air capture, a specific process that uses machines to “capture” carbon dioxide directly out of the atmosphere. As such, direct air capture technology (DAC) is a promising complementary approach to sustainable development that could help certain industries like aviation reach their net-zero carbon emissions targets. 

Direct air capture is location-independent, meaning they can be situated anywhere in the world. Unlike the aforementioned methods, DAC does not require geographic attachment to an emissions source such as a power plant to function as intended. They also do “not compete for land needed to grow food and do not require long-distance CO2 transportation.” Additionally, once carbon dioxide is captured from the air, DAC can either store the gas or recycle it to produce “long-lived products such as cement or building insulation.” A continuous recycling of carbon dioxide is crucial to reducing emissions and maintaining a healthy, sustainable planet. 

Despite these benefits, there are several challenges to deploying DAC at the level deemed necessary by climate information models. Current technologies would require the construction of about “30,000 factories with significant resource implications, including the carbon footprint of mining, refining, and manufacturing the essential metals and concrete.” This involves serious resource limitations and risks, making cost recovery a major challenge. 

Ocean Alkalization

Ocean alkalization is another approach to carbon dioxide removal that involves the deployment of alkaline substances and carbonate minerals into the ocean to enhance the natural carbon storage capacity of seawater. Adding these substances to the ocean, according to the EU-funded OceanNETs project, will “not only increase CO2 uptake by the ocean, but it would also counter seawater acidity generated by excess anthropogenic CO2.”

Ocean alkalization combats ocean acidification and protects marine ecosystems and their food supply. The electrochemical production of ocean alkalinity, moreover, co-produces hydrogen which can then be used for energy. 

However, there have been a number of concerns raised by lawmakers and environmentalists on the overall efficiency of ocean alkalinity: firstly, the method is resource-demanding. Substantial mining and processing of raw materials is required, along with an abundance of energy for proper use. Secondly, there is insufficient research on the potential biogeochemical effects of adding alkaline substances to the ocean and how it can change ocean chemistry. This has caused uncertainty regarding the environmental benefits of ocean alkalization, prompting an interest in the potential mitigating effects of ocean fertilization. 

Ocean Fertilization

Ocean fertilization is a form of geoengineering that involves the systematic addition of plant nutrients such as iron or nitrogen to surface waters to increase phytoplankton growth, i.e. photosynthesis, and ultimately reduce atmospheric CO2 levels. This approach mostly occurs in specific ocean regions where phytoplankton growth and productivity is low. 

The resultant phytoplankton growth from ocean fertilization, in addition to increasing CO2 absorption, releases a compound called “dimethyl sulfide into the air that has the ability to cool the atmosphere and further help reduce global warming.” On top of that, the cost estimate of nutrient distribution into the ocean is significantly lower than the current cost of other carbon sequestration mechanisms.

Despite the obvious cost benefit, some scientists contend that fertilization may cause more environmental harm than good. They maintain that accelerating the growth of phytoplankton may negatively impact marine food chains. A Britannica article doubled down on this, suggesting that “some species of phytoplankton might be better than others at incorporating the nutrients provided by the fertilization.” This would subsequently affect the zooplankton’s eating habits, an organism that feeds on the phytoplankton. 

Simone Tilmes of the National Center for Atmospheric Research has also argued that “despite its potential to create overall cooling, ocean fertilization could cause significant changes in localized temperature and precipitation.” These changes can damage the ozone layer and therefore expose ultraviolet radiation to Earth’s surface, a catastrophic potentiality. 

Coastal Blue Carbon

Coastal blue carbon is a scientific term that refers to the carbon stored in coastal marine ecosystems such as mangrove forests, tidal and salt marshes, and seagrasses. These “coastal blue carbon” ecosystems then gradually accumulate and store a significant amount of carbon in plant sediments and biomass. 

These kinds of ecosystems provide a number of benefits for climate change adaptation in coastal areas. Specifically, this includes protection from storms and floods, a drastic improvement of coastal water quality, shoreline control and stability, and food security for coastal marine organisms. But most importantly, these ecosystems are valuable because of their inherent capacity to sequester carbon dioxide from the atmosphere.

Though many studies have favorably recognized the potential of coastal blue carbon sequestration, there has been increased concern over their endangerment and the negative effects of degradation. According to the Blue Carbon Initiative, an estimated “340,000 to 980,000 hectares of coastal blue carbon ecosystems are destroyed each year.” When these ecosystems are lost or degraded, their carbon storage is released in the form of “methane, carbon dioxide, and nitrous oxide,” thus becoming a major source of greenhouse gas emissions and accelerating planetary warming.

Environmental activists and policymakers alike have stressed the climate mitigation value of coastal blue carbon ecosystems and the urgent need to protect their sustenance.


Mineralization, in the carbon cycle, is the process by which carbon dioxide turns into a solid mineral. This occurs when certain rocks are exposed to carbon dioxide, upon which said carbon dioxide is trapped in the crystal structure of minerals.

The most significant benefit of carbon mineralization is that the trapped CO2 can no longer escape back or leak into the atmosphere. Mineralized rocks are essentially a permanent storage unit for carbon. In addition to their sequestering purpose, carbon mineralization can also “fortify and de-acidify soil and water” and thus promotes environmental sustainability and ocean purity. And because mineralization is used to produce carbonate products and services, they can enter the economy and generate jobs, inspire innovation, and improve national GDPs. 

But there are also several risks associated with carbon mineralization. The mineralization process often requires mining, which comes with its own set of challenges including the “disruption of natural ecosystems, human health and safety, and pollution.” Mining can also contribute to a decline in biodiversity, soil erosion, and the contamination of groundwater.

Open Ocean Seaweed Growth and Sinking

Sinking seaweed and other carbon-rich macroalgal biomass into the deep ocean floor may play an important role in marine carbon sequestration. This process involves the collection or growth and sinking of seaweed deep into the ocean, where the carbon held in that seaweed is stored for hundreds or even thousands of years.

But also, seaweed has been particularly noted for its ability to regenerate marine ecosystems, create biofuels and renewable plastics, and produce marine protein. Unlike planting trees, seaweed does not require fresh water or fertilizers and grows at a much faster rate. And most importantly, this method does not impose any demands on land. This makes seaweed farming a viable, environmentally friendly approach to carbon sequestration and, on a broader scale, a strong component of the ocean economy.

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