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What is direct air capture (DAC) technology and its advantages and disadvantages?

Direct air capture (DAC) is a carbon reduction technique that draws air from the atmosphere and then uses a chemical reaction to separate the carbon dioxide.

The captured carbon dioxide can be stored underground or used to make durable materials such as cement and plastic. The purpose of direct air capture is to use technical means to reduce the overall concentration of carbon dioxide in the atmosphere. That way, direct air capture could, along with other initiatives, help mitigate the devastating impacts of the climate crisis.

According to the International Energy Agency (IEA ), there are 15 direct capture plants operating in the United States, Europe and Canada. These plants capture more than 9,000 tons of carbon dioxide per year. The United States is also developing a capture device direct gas has the potential to remove 1 million tons of carbon dioxide from the air each year.

The United Nations Intergovernmental Panel on Climate Change (IPCC) has warned that to keep atmospheric carbon dioxide below 440 ppm and global temperature rise below 2 degrees Celsius (3.6 degrees Fahrenheit), global carbon dioxide emissions must be reduced by 30% to 85% by 2050. Direct air capture can it help reduce emissions?

To slow climate change, scientists and economists from the Intergovernmental Panel on Climate Change agree that the Long-term measures are needed to reduce human-caused greenhouse gas emissions. Direct air capture technology has been widely criticized as insufficient to reduce harmful carbon dioxide in the atmosphere. Additionally, the cost per ton of CO2 captured is higher than other strategies to mitigate the climate crisis.

1. How Direct Air Capture works

What is Direct Air Capture (DAC) technology and its advantages and disadvantages It?

Direct air capture uses two different methods to remove carbon dioxide directly from the atmosphere. The first method is to use a solid absorbent to absorb carbon dioxide. An example of a solid adsorbent is a basic chemical placed on the surface of a solid material. As air flows over the solid adsorbent, a chemical reaction occurs that combines the acidic carbon dioxide gas with the alkaline solid. When the solid adsorbent is filled with carbon dioxide, it is heated to 80°C to 120°C or a vacuum is used to absorb the gas from the solid adsorbent, and the solid adsorbent can be cooled and used. reuse.

Another type of direct air collection system uses a liquid solvent, which is a more complicated process. The first is a large container in which a solution of potassium hydroxide (KOH) flows over the surface of the plastic. Air is drawn into the container by a large fan and when the air containing carbon dioxide comes into contact with the liquid, the two chemicals reactants form a carbon-rich salt.

The salt flows into another chamber where another reaction takes place, creating a mixture of solid calcium carbonate particles (CaCO3) and water (H2O). A mixture of calcium carbonate and water is filtered to separate the two substances. The final step in the process uses natural gas to heat solid calcium carbonate particles to 900°C, releasing pure carbon dioxide gas high, then collected and compressed.

The remaining materials are recycled into the system for reuse. Once captured, carbon dioxide can be permanently injected into the system. underground rock blocks to help revive old oil wells or used in durable products such as plastics and construction materials.

2. The difference between direct air capture and carbon capture and storage

Many experts believe that both direct air capture and carbon capture and storage systems Carbon storage (CCS) are all key technologies to mitigate the climate crisis. Essentially, both technologies reduce the amount of carbon dioxide in the atmosphere. However, unlike direct air capture, CCS uses a chemical to capture carbon dioxide directly from the source. waste. This prevents carbon dioxide from entering the atmosphere. For example, CCS can be used to capture and compress all the carbon dioxide emitted from coal-fired power plant chimneys. On the other hand, direct air capture captures carbon dioxide that has been released into the air from coal-fired power plants or other fossil fuel burning activities.

Both direct air capture and CCS both use basic chemicals, such as potassium hydroxide and amine solvents, to separate carbon dioxide from other gases. Once CO2 is trapped, both processes must compress, transport and isolate the gas. Although CCS technology is a bit more mature than direct air capture technology, both are relatively new technologies that could benefit from further development.

By because CCS removes carbon dioxide from the source,it can only be used in places where fossil fuels are burned, such as industrial facilities and power plants. In theory, direct air capture can be used anywhere, although placing it near a power source or somewhere that can sequester carbon dioxide will increase its effectiveness.

3. The Development Status of Direct Air Capture

According to the World Resources Institute, there are three leading direct air capture companies in the world: Clime⁃works in Switzerland Si, Global Thermostat in the United States and Carbon Engineering in Canada. Two of them use solid adsorption technology to remove carbon dioxide, while the third third uses liquid solvent carbon techniques.  The number of operational and pilot plants varies from year to year, but the world's first commercial-scale DAC facility currently removes 900 tons of CO2 per year and several commercial facilities are under construction.

What is direct air capture (DAC) technology and its advantages and disadvantages?

For the past 15 years, a direct air capture pilot plant in Squamish, British Columbia, Canada has uses renewable electricity and natural gas to fuel a liquid solvent process that removes 1 ton of carbon dioxide per day. The company is currently building another direct air capture facility capable of capturing capture 100 million tons of carbon dioxide per year.

Another direct air capture plant to be built in Iceland will be able to capture 4000 tons of carbon dioxide per year and then permanently store the compressed air underground. The company that built the plant now has 15 smaller direct air capture plants around the world.

4. Pros and cons of direct air capture

The most obvious advantage of direct air capture is its ability to reduce carbon dioxide concentrations in the atmosphere. Not only is it more widely used than CCS, it also takes up less space to capture the same amount of carbon than other carbon sequestration technologies. In addition, direct air capture can also be used to make synthetic hydrocarbon fuels. But to be effective, the technology must be sustainable, inexpensive and scalable. To date, direct air capture technology has not been able to meet these requirements.

a. Advantages

Companies specializing in direct air capture technology are now developing new, larger direct air capture plants with capacities up to 100 million tons of CO2 per year. If direct air capture devices are made small enough, they could capture up to 10% of human-generated carbon dioxide. By injecting and sequestering carbon dioxide into the ground, carbon can be permanently removed from the cycle.

Because it relies on capturing carbon dioxide from the atmosphere rather than directly from the gas fossil fuel emissions, direct air capture can operate independently of power plants and other plants that burn fossil fuels. This allows for more flexible and widespread placement of direct air capture plants.

Compared to other carbon capture technologies, direct air capture does not require as much land per tons of carbon dioxide removed.

In addition, direct air capture can reduce the need for fossil fuel extraction and the amount of carbon dioxide released into the atmosphere can be further reduced further by combining the resulting carbon dioxide with hydrogen to produce synthetic fuels such as methanol.

b. Disadvantages

Direct air capture is more expensive than other carbon capture technologies, such as afforestation and reforestation. Some direct air capture plants currently cost between $250 and $600 per ton carbon dioxide, with estimates ranging from $100 to $1000 dollars per ton and future direct air capture costs The future is uncertain, according to researchers at the European Institute for Economic and Environmental Research RFF-CMCC, as it will depend on the pace of technological progress. However, the cost of afforestation is only 50 USD/ton.

The high cost of direct air capture technology is that it requires a lot of energy to remove carbon dioxide. The heating process for direct air capture of liquid solvent and solid sorbent is energy intensive, as it requires chemical heating to 900°C and cooling to 80°C -120°C. Unless a nhWhile a direct air receiver only relies on renewable energy to generate heat, it will still need to use some fossil fuels, even if the process is ultimately carbon negative.