Direct air capture (DAC) is a method that uses chemical or physical processes to remove carbon dioxide (CO₂) directly from the air around us. If the captured CO₂ is stored safely for a long time, the process is called direct air carbon capture and sequestration (DACCS), which helps reduce CO₂ in the atmosphere. Systems that do this are known as negative emissions technologies (NET).
DAC differs from carbon capture and storage (CCS), which removes CO₂ from specific sources, like a factory or a power plant. After capture, DAC creates a concentrated CO₂ stream that can be stored or used. CO₂ removal happens when air interacts with chemical materials, such as a water-based alkaline solution or special absorbents. These materials are then heated to remove CO₂, which can be dried and compressed, while the materials are reused.
DAC is not yet part of emissions trading because it costs more than $1,000 per ton of CO₂, which is much higher than the current carbon price. High costs are due to the size of operations and energy use. In 2025, DAC costs were over $1,000 per ton of CO₂. Some experts believe that if DAC plants operate at large scales (1 million tonnes per year or more), costs could drop below $200 per ton of CO₂ removed, but others disagree. Future improvements might lower the energy needed for the process.
DAC was first proposed in 1999 and is still being developed. Some commercial plants are planned or already operating in Europe and the United States. Large-scale use of DAC may increase if linked to cost-effective uses or supported by policies.
Unlike CCS, which removes CO₂ from a single large source like a factory, DAC reduces CO₂ levels in the entire atmosphere. Air travel and space exploration are expected to produce significant greenhouse gases by the middle of the 21st century. DAC can capture CO₂ before or after it is used in jet fuel. While biofuels are an alternative to synthetic fuels (efuels), as of 2026, the most sustainable balance between them is not clear.
Methods of capture
Direct Air Capture (DAC) involves three main stages: contacting, capture, and separation. In the contacting stage, large fans move air containing carbon dioxide (CO₂) into the DAC system. During the capture stage, CO₂ attaches to liquid solvents in chemical reactors or solid materials in filters. These materials must have strong enough chemical bonds to hold CO₂ securely. In the separation stage, energy is used to remove CO₂ from the solvents or filters, producing pure CO₂ and regenerating the materials for reuse. After these steps, the pure CO₂ is either used or stored, and the materials are reused in the capture process.
Solid sorbent DAC (S-DAC) typically uses low-temperature processes, while liquid sorbent DAC (L-DAC) can use low- or high-temperature processes. S-DAC and L-DAC differ in how quickly they work and how heat moves through them. Both are established technologies for industrial use. Other newer DAC methods, such as electro-swing adsorption (ESA), moisture-swing adsorption (MSA), and membrane-based DAC (m-DAC), are being tested or used in limited ways.
A company in Ireland, Carbon Collect Limited, created the MechanicalTree™, a device that captures CO₂ passively by standing in the wind. The company claims this method lowers energy costs and allows the technology to scale for capturing large amounts of CO₂.
Most commercial DAC systems use liquid solvents, such as amine-based or caustic (sodium hydroxide) solutions, to absorb CO₂ from air. Sodium hydroxide reacts with CO₂ to form sodium carbonate, which is heated to produce pure CO₂ gas. Sodium hydroxide can be recovered from sodium carbonate through a process called causticizing. Alternatively, CO₂ can bind to solid materials through chemisorption, and heat or vacuum can then remove CO₂ from the solid.
Some specific chemical processes being studied include using alkali or alkali-earth hydroxides, carbonation, and hybrid materials made of amines attached to porous structures.
The idea of using many small DAC units, similar to trees, to reduce CO₂ levels has led to the nickname "artificial trees."
In 2012, professor Klaus Lackner developed a method using an anionic exchange polymer resin called Marathon MSA. This material absorbs CO₂ from dry air and releases it when exposed to moisture. The process uses energy from water’s phase changes, but more research is needed to assess its cost-effectiveness.
Metal–organic frameworks (MOFs) are materials made of metal clusters connected by organic molecules, forming highly ordered structures with large internal surfaces. Compared to traditional materials like activated carbon or zeolites, MOFs can be tailored to have specific pore sizes and chemical properties. Amine-functionalized MOFs are especially promising for DAC because they can bind CO₂ even at low atmospheric concentrations (about 400 ppm). However, MOFs must be made stable against moisture, as water in air can damage their structure over time. Research is ongoing to improve their humidity resistance.
Finding effective MOF materials for DAC is difficult due to the many possible combinations. In 2023, researchers from Meta AI and Georgia Tech released the OpenDAC dataset, which includes results from 400 million computer calculations screening MOFs for CO₂ adsorption. The dataset also includes tools to speed up material discovery.
Membrane-based DAC (m-DAC) uses semi-permeable membranes to separate CO₂. These membranes require little water and have a small footprint. Polymeric membranes, such as glassy or rubbery types, are commonly used. Glassy membranes are highly selective for CO₂ but allow it to pass slowly. This method is still being developed and needs more research before large-scale use.
Electro-swing adsorption (ESA) is another proposed method.
Rock flour, which is soil ground into tiny particles by glaciers, has potential as both a soil enhancer and a CO₂ capture material. Glaciers deposit about one billion tons of rock flour annually, and one ton of Greenlandic rock flour can capture 250 kilograms of carbon.
Environmental impact
Direct Air Capture (DAC) is a technology that removes more carbon dioxide (CO₂) from the air than it emits. When using renewable electricity, DAC emits about 0.01 tons of CO₂ for every ton of CO₂ captured. However, when using electricity from the grid and natural gas for heating, DAC may emit up to 0.65 tons of CO₂ for every ton of CO₂ captured. The type of energy used is the main reason for DAC’s greenhouse gas (GHG) emissions. Using a mix of renewable wind energy and grid electricity can still make DAC carbon negative, as long as wind energy supplies at least 50–80% of the plant’s energy needs and grid electricity emissions are less than 0.3077 kilograms of CO₂ per kilowatt-hour. If grid electricity has higher emissions, its use must be limited to less than 20% to achieve strong carbon removal.
Supporters of DAC say it is important for reducing climate change. Scientists believe DAC could help meet the Paris Agreement’s goal of limiting global temperature rise to well below 2°C. The International Energy Agency (IEA) estimates that capturing at least 85 million and 980 million tons of CO₂ annually by 2030 and 2050, respectively, is needed to reach net zero emissions. However, some people argue that relying on DAC might delay efforts to reduce emissions, as it could create the idea that problems can be fixed later. They suggest that reducing emissions directly is a better solution. It is important to view DAC as a tool that can help achieve climate goals, but not the only solution.
Critics of DAC say the technology requires large amounts of resources that might make it less effective. A 2020 study found that DAC 2 technology might not be able to capture the projected 30 gigatonnes of CO₂ per year, as it would need massive amounts of materials, such as 16.3–27.8 gigatonnes of ammonia and 3.3–5.6 gigatonnes of ethylene oxide. The same study said DAC 1 technology would need at least 8.4–13.1 terawatt-years of energy, but this estimate did not include energy costs for storing CO₂. However, the IEA’s net zero plans require capturing only 0.1 gigatonne of CO₂ annually by 2050, which is much less than the 30 gigatonnes critics are concerned about.
In 2021, researchers studied the energy costs of DAC. They found that to capture 73–86% of CO₂ per ton captured, DAC would need land and renewable energy similar to what is needed to switch all gasoline vehicles to electric vehicles, but with five times more material use. Most of the materials needed for DAC are common, like steel, concrete, and minerals such as zeolites and metallic hydroxides. Electric vehicles also need critical materials, which might be limited and not enough for net zero goals.
Some DAC systems, especially liquid ones, need both high heat and electricity. These systems often use natural gas, grid electricity, or natural gas combustion for heat. This means some DAC technologies rely on fossil fuels, which they aim to reduce. However, even with natural gas use, DAC is still generally carbon-negative, with emissions ranging from 0.3 to 0.65 tons of CO₂ per ton of CO₂ captured.
DAC that uses amine-based absorption requires large amounts of water. Capturing 3.3 gigatonnes of CO₂ annually would need about 300 kilometers of water, or 4% of the water used for irrigation. In contrast, using sodium hydroxide needs less water, but the chemical is very dangerous. Different carbon removal methods have their own advantages. For example, nature-based solutions are cheaper, but a DAC plant capturing 1 million tonnes of CO₂ annually would need 0.4–1.5 square kilometers of land, equivalent to the CO₂ removal of about 46 million trees, which would require 3,098–4,647 square kilometers of land.
DAC requires more energy than traditional methods of capturing CO₂ from sources like power plant flue gas because CO₂ in the air is less concentrated. The minimum energy needed to extract CO₂ from air is about 250 kilowatt-hours per tonne of CO₂. Capturing CO₂ from natural gas and coal plants requires about 100 and 65 kilowatt-hours per tonne of CO₂, respectively. Additional energy costs from using fans to move air could increase energy use by 10–30%, depending on the energy demand.
Applications
Practical uses of DAC include various industries that require different amounts of CO₂ produced from captured gas. Methods like geological storage need very pure CO₂ (more than 99%), while other uses, such as agriculture, can work with less concentrated CO₂ (about 5%). The air processed by DAC originally contains 0.04% CO₂ (or 400 ppm). Creating pure CO₂ requires more energy and is usually more expensive than producing less concentrated CO₂. Carbon used for food production typically needs higher purity, ranging from 50% or more, followed by further chemical processing.
DAC is not a replacement for traditional carbon capture and storage (CCS) methods, but it can work alongside them. It helps manage carbon emissions from scattered sources, leaks from CCS systems, and emissions from geological storage. Because DAC can be placed far from pollution sources, synthetic fuels made using this method can use existing fuel transport systems.
Most discussions about DAC focus on its ability to reduce climate change. However, most current DAC facilities are small and mainly sell captured CO₂ for other uses rather than permanently storing it. Facilities that sell CO₂ for beverage production have low recovery rates, about 4.7%, and produce 58 metric tons of CO₂ per day. Using DAC for commercial purposes supports the view held by some that DAC is a strategy used by companies to protect their financial interests.
Because DAC has many uses, supporters believe the technology can create new job opportunities.
Operational/developing DAC facilities
Direct Air Capture (DAC) Projects and Their Processes for Removing and Storing Carbon
Direct air capture (DAC) technologies are being developed to help China reach its goal of reducing carbon emissions to zero by 2060. After the 2021 Glasgow Climate Conference, China, the largest emitter of greenhouse gases, started creating plans to reduce emissions. If China uses DAC technology alone, it could help lower global warming by about 0.2°C to 0.3°C. Studies show that China can achieve carbon neutrality by using carbon capture and storage to remove several billion tons of carbon dioxide (CO₂) each year from sources like factories. China has created its own DAC technology called "CarbonBox," developed by Shanghai Jiao Tong University and China Energy Engineering Corporation. Each unit of CarbonBox can remove over 100 tonnes of CO₂ annually, producing CO₂ that is 99% pure. CarbonBox facilities are the size of shipping containers, can be placed at specific locations, and use low-carbon energy to remove CO₂ from the air.
The Orca, created by Climeworks in Zurich with support from Microsoft in 2021, was the first large-scale DAC plant. It was designed to remove 4,000 tonnes of CO₂ each year, which is equal to about 1.75 million liters of gasoline. However, the plant has only removed an average of 600 tonnes of CO₂ annually since it started operating, which is not enough to cover its own emissions. The Orca facility is located in Iceland at Hellisheidi and is powered by the Hellisheidi Geothermal Power Plant. It uses 12 containers that hold a chemical called amine to capture about 600 kilograms of CO₂ each hour. The captured CO₂ is sent to CarbFix, an Icelandic company that injects the CO₂ into the Earth’s crust through a process called mineralization. This process prevents risks like fires or leaks that can happen with other DAC methods.
Octavia Carbon, started by Martin Freimüller in 2022, is the first DAC company in the Global South. The company plans to develop DAC technology that works with Kenya’s renewable energy sources and its geology, which is suitable for storing CO₂. This project is still being developed, but with support from the Kenyan government and other DAC companies, the team now has 53+ employees. Octavia Carbon is working with Carbonfuture to use a digital Monitoring, Reporting, and Verification (dMRV) system, which tracks carbon removal data in real time. The current test facility, called Project Hummingbird, is located in Kenya’s Rift Valley near Naivasha and is expected to capture and store 1,000 tonnes of CO₂ each year. Project Hummingbird will use mineralization by injecting CO₂ into basalt rock formations found in the Rift Valley.
Cost
One of the biggest challenges in using DAC technology is the high cost of removing CO₂ from the air. In 2023, the United States Department of Energy aimed to reduce the cost of capturing CO₂ to less than $100 per tonne. The largest DAC plant today, Climeworks Mammoth, can capture 36,000 tonnes of CO₂ each year, but it costs $1,000 (£774) per tonne to do so. A 2025 study found that the high cost is partly because the plant's size is small, usually under 50,000 tonnes per year. Larger DAC plants can lower costs through economies of scale. For example, a plant that captures 1 million tonnes of CO₂ annually could cost between $94 and $232 per tonne. Government policies can help speed up the use of large-scale DAC technology.
Under the Bipartisan Infrastructure Law, the U.S. Department of Energy will spend $3.5 billion to build four direct air capture hubs. These hubs are expected to capture at least 1 million metric tonnes of CO₂ each year from the atmosphere. After capture, the CO₂ will be stored permanently in underground rock formations. The Department of Energy has already invested $1.2 billion to support direct air capture projects in Texas and Louisiana. These projects were chosen as part of the Bipartisan Infrastructure Law.
Development
Carbon Engineering is a company that removes carbon dioxide (CO2) from the air. It was started in 2009 and is supported by people like Bill Gates and Murray Edwards. By 2018, it operated a test facility in British Columbia, Canada, which began working in 2015. This facility can remove about one tonne of CO2 each day. A cost study from 2015 to 2018 estimated that removing one tonne of CO2 from the air cost between $94 and $232. A 2025 study agreed with these numbers, stating that removing CO2 would cost between $97 and $168 per tonne if the plant could capture at least one million tonnes of CO2 per year. If the plant could capture less than 50,000 tonnes per year, the cost would be more than $1,000 per tonne. Climeworks, another company, has a plant called Mammoth in Iceland that removes 36,000 tonnes of CO2 annually, which is currently the largest direct air capture (DAC) plant.
Carbon Engineering works with Greyrock, a California energy company, to turn some of the captured CO2 into synthetic fuels like gasoline, diesel, and jet fuel. The company uses a chemical called potassium hydroxide, which reacts with CO2 to form potassium carbonate, removing CO2 from the air.
Climeworks started its first large-scale DAC plant in Switzerland in 2017. This plant captures 900 tonnes of CO2 each year and uses heat from a nearby waste incineration plant to reduce energy needs. The captured CO2 is used to help grow vegetables in a greenhouse. Climeworks also partnered with Reykjavik Energy on a project called Carbfix, which began in 2007. In 2017, the CarbFix2 project started and received funding from the European Union. This project injects CO2 700 meters underground in Iceland, where it turns into solid minerals. The DAC plant uses heat from a nearby geothermal power plant, reducing its overall CO2 emissions.
In 2024, Climeworks opened the Mammoth plant in Iceland, which can remove 36,000 tonnes of CO2 annually. This is equivalent to removing the emissions from about 7,800 gas-powered cars each year. The cost to capture CO2 at this plant is estimated at $1,000 per tonne. This high cost is partly because the plant is not yet large enough to benefit from lower costs associated with larger operations. A plant that captures one million tonnes of CO2 annually would cost between $94 and $232 per tonne. A project called Cypress aims to build such a large plant in the United States.
Global Thermostat is a company founded in 2010 in New York. It has a facility in Alabama that uses special materials to remove CO2 from the air. The company has agreements with Coca-Cola and ExxonMobil to use its technology for producing carbonated drinks and synthetic fuels.
Soletair Power is a startup in Finland that began in 2016. It combines DAC with building heating, ventilation, and air conditioning (HVAC) systems to capture CO2 from the air inside buildings. The captured CO2 is turned into concrete or used to make synthetic products like food, textiles, or fuel. In 2020, Soletair Power, along with other companies, built a demonstration unit for Dubai Expo 2020 that produces synthetic methane from captured CO2.
Prometheus Fuels is a startup in Santa Cruz, California, that started in 2019. It uses DAC technology to remove CO2 from the air and convert it into gasoline and jet fuel using electricity from renewable sources. These fuels are carbon neutral, meaning they do not add extra CO2 to the atmosphere when used.
Heirloom opened a DAC facility in Tracy, California, in 2023. This facility removes up to 1,000 tonnes of CO2 annually, which is mixed into concrete using technology from CarbonCure. Heirloom also has a contract with Microsoft to purchase 315,000 metric tonnes of CO2 removal.
Researchers at ETH Zurich developed a new chemical method for DAC using a photoacid solution. This method requires less energy and may be easier to scale up. Recent studies suggest that using warehouse automation systems in DAC facilities could lower costs and improve efficiency by making operations smoother.
Political discourse
In the United States, there is disagreement between politicians and people who are not part of any political group but care about the environment. This disagreement is about a technology called Direct Air Capture (DAC), which is meant to help reduce the risks of climate change. Some people believe DAC is not the best way to address climate change, while others think it could be useful.
One major concern from environmental activists is that DAC is seen as too expensive and not helpful enough compared to the need to reduce emissions. Some believe DAC is used to keep the fossil fuel industry strong and continue pollution. For example, The Stratos Project was bought by Occidental Petroleum for $1.1 billion. This company, which is an American oil company, also bought Carbon Engineering in 2023 for the same amount. It views carbon removal as a way to protect its industry in the future. Jonathan Foley, who leads Project Drawdown (a plan to stop climate change), says DAC is a way for companies to appear environmentally friendly without solving real problems. In Penang, the Consumer's Association believes DAC makes the climate crisis worse and goes against the idea of fairness in addressing climate change.
A 2024 study looked at how people in the United States feel about DAC. It found that many people who know about DAC and care about climate change are worried about the risks it might bring. Some people are upset that DAC could let companies keep polluting while pretending to be eco-friendly. Others fear that fossil fuel companies might use DAC to make it look like they are helping the environment without actually making a real difference.
Environmentalists also worry about the effects of DAC on the environment. They are concerned about how the energy systems needed for DAC might harm air quality in certain areas. Some people object to DAC because they believe these projects are often built in poor communities, where people feel they are being treated unfairly.
Another study from the United States and the United Kingdom found similar views. People thought DAC is not a good solution for the future because it does not solve the main causes of climate change. They described DAC as a way to respond to climate change after it happens, not a way to prevent it. The study also showed that few people believe DAC deals with the root cause of emissions. Overall, people think DAC is not a real solution but instead helps the companies that cause the climate crisis.
Political leaders are also unsure about DAC because they question whether it can be used widely and successfully. Other technologies like carbon capture and storage (CCS) and bioenergy with carbon capture and storage (BECCS) have faced public opposition and failed projects, which makes people doubt DAC.
Some environmentalists think the $3.5 billion investment in DAC is risky for communities that are already struggling. The Institute of Policy Studies says this investment could harm these communities if DAC does not work as planned. Surveys show that people do not trust local governments or fossil fuel companies that support DAC. After a 2020 report found that most tax credits for carbon capture were used without proof that carbon was captured, people became less confident in government programs. The IRS not sharing details about which companies benefit from DAC investments also makes people unsure about how their taxes are being used.
A 2023 poll showed that 42% of Democrats strongly support DAC, 34% of independent voters support it, and only 28% of Republicans support it. Even though many environmentalists are against DAC, it has received support from both major political parties in the government.
The reason for this support is that DAC may help the environment and create economic benefits. Republicans believe DAC can create jobs, increase tax revenue, and help local economies. Many fossil fuel companies, like ExxonMobil, also support DAC research because it protects their industry. Even though there is bipartisan support for DAC in Congress, a 2024 survey found that Republicans and Independents are less likely than Democrats to support building DAC projects in their communities or the United States.
Most discussions about DAC come from environmental activists. While Republicans and Democrats have different views on DAC, these differences are mostly about how useful they think DAC is. Democrats often see DAC as a possible solution to global warming, while Republicans support it because they believe it will not harm the economic interests of fossil fuel companies.
Direct air capture shortcomings
Bioenergy with carbon capture and storage (BECCS) has faced criticism for several reasons, mainly because the technology uses a lot of energy, needs large areas of land, and may release carbon dioxide back into the atmosphere. Environmental groups say BECCS is not a practical solution because the project could create emissions. BECCS is suggested as a way to reduce carbon based on the idea that bioenergy is carbon neutral. However, this idea is wrong because many believe that cutting down forests, logging, and using land for this technology could cancel out the carbon it removes. People who care about protecting animals argue that needing more land for BECCS could harm wildlife and reduce biodiversity. Others worry that the chance of carbon dioxide leaking from storage sites is too high to ignore. If carbon dioxide stored underground leaks, it could cause serious problems. "Atmospheric CO2 levels could rise quickly, especially if a major storage site leaked." Concerns about CO2 leakage are common among people who doubt direct air capture (DAC).
Direct air capture (DAC) uses a lot of energy, with estimates ranging from 1 to 2.5 million kilowatt-hours of electricity per tonne of CO2 removed. A 2026 study found that removing 2 gigatonnes of CO2 each year would need more than half of the electricity produced in the United States in 2024. However, heat pumps and geothermal energy could be used to help with this process.