Can CO2 be captured from the atmosphere mechanically?

CO2 in the air is naturally absorbed through what are called large carbon sinks, mainly forests and oceans. But as the amount of carbon dioxide in the atmosphere increases and natural reservoirs begin to saturate, humans are finding new ways to absorb that CO2. How? By using machines.

There are a number of companies around the world that are installing large turbines dedicated to filtering CO2 from the air to  keep it in a tank or pump it into the ground.

Now, a group of scientists has investigated the effectiveness of this system, which is often viewed with skepticism by experts. conservation organization, because the amount of gas that needs to be processed is very large to be able to collect significant amounts of CO2.

The research was carried out by scientists at the Paul Scherrer Institute (PSI) and ETH Zurich , Switzerland, and have shown that through careful planning (especially in the choice of location and the power supply required for these systems), CO2 can be effectively removed. effective. The results were published in the journalEnvironmental Science & Technology.

System to absorb CO2 from the air in Switzerland. Photo: Climeworks.

Direct air carbon capture (DACCS) is a relatively new technology, so these scientists wanted to test the usefulness of this process.
In this way, they studied a total of five different facilities to capture CO2 from the air in eight different locations around the world, including Spain. As a result, depending on the combination of technology used and the specific location,up to 97% of carbon can be removed from the air.
To separate CO2 from the atmosphere, air is first fed into a mechanism called an absorber, with the help of powerful fans. The CO2 remains there until it enters the second stage, called desorption, where carbon dioxide is released back from the absorber, ready for storage.
Depending Depending on the configuration of the absorber, the process can take place at very high temperatures, up to 900 degrees Celsius, or at relatively low temperatures, 100 degrees Celsius.

Process of absorbing CO2 from air

Process to absorb CO2 from air

In addition to the energy required to manufacture and install the equipment, the operation of powerful fans and the generation of heat required for the process also generate greenhouse gas emissions. Therefore, assessing how effective the system is is important to determine whether CO2 sequestration can compensate for the emissions it produces.

"Using this technology only makes sense if the emissions produced are significantly lower than the amount of CO2 it helps capture," Tom Terlouw, first author said the first of the research.

In their research, experts focused their work on the system installed by the Swiss company Climeworks, which operates with a temperature process High. Additionally, PSI researchers analyzed the performance of this technology in eight different locations around the world: Chile, Greece, Jordan, Mexico, Spain (Tabernas), Iceland, Norway and Switzerland.

For each location, they calculated the total greenhouse gas emissions produced over the entire life cycle of the plant. For example, they compared the efficiency of the process when the electricity came from solar power or from the conventional grid.

Result: 9% to 97% efficiency

Efficiencies obtained at these eight sites and the five systems used in each site were found to vary widely in terms of CO2 capture. < strong>While in some cases only 9% greenhouse gas removal was achieved with this method, in other cases it reached 97%.

The bottom line The bottom line is that "CO2 capture technologies only complement the global decarbonization strategy, but they cannot replace it," according to Christian Bauer, co-author of the study.

"In any case, theycan be useful to achieve the goals defined in the Paris Agreement on climate change, since some emissions, for example from agriculture, cannot be avoided.” Therefore, he added that the target of net-zero emissions can only be achieved with the help of appropriate technologies.

Gas capture turbine

Gas capture turbine. Photo: Climeworks

Environmentalists schools do not appreciate these facilities. In Spain, Paco Ramos, of the organization Ecologists in Action, told Verde y Azul: "The problem is discrimination. canopy. To capture 8 million tons of CO2 from the atmosphere, 20 billion tons of air would have to be processed, as most of it is nitrogen. Therefore, these projects are "completely unfeasible," he said.

There is a second system for mechanical CO2 capture, which occurs directly in industrial generation facilities. produce it (like power plants). A system is responsible for capturing CO2 before it escapes through the chimney and is then stored underground.

According to Ramos, capture within the same thermal power plant is somewhat effective. more efficient and has been done in many places, but "even so, to capture 8 million tons of carbon dioxide, you have to have a machine that captures 80 million tons of air." "You have to build thousands of such machines to see their impact," he said.

In addition, it is also an expensive process, which is why Ramos mentioned reminds us: "The only viable method of capture is that carried out by the trees and the sea; They have maintained the balance so far" .