New Study on Direct Air Capture Offers Hope to Reduce Carbon Emissions

Direct Air Capture (DAC) technology is considered to be an essential tool in the fight against climate change.

The Intergovernmental Panel on Climate Change (IPCC) has identified DAC technology as a key technology that will be needed to achieve the goal of net-zero greenhouse gas emissions by 2050, which is necessary to limit global warming to 1.5 degrees Celsius above pre-industrial levels.

A new research article published on Science.org^[1] discusses the extended applications and new opportunities for the DAC technology.

Understanding the New Study on Direct Air Capture

The low concentration of atmospheric CO₂, which is around ~400 parts per million, makes it difficult to capture high volumes of CO₂ using sorption-desorption processes, using the existing methods for DAC.

To overcome this challenge, researchers have developed a new hybrid sorbent that uses a polyamine-Cu(II) complex to create a Lewis acid-base interaction.

This hybrid sorbent has a much higher CO₂ capture capacity than most of the other DAC sorbents reported to date, with the ability to capture over 5.0 mol of CO2 per kg of sorbent^[2].

This capacity is two to three times greater than most other DAC sorbents.

One of the advantages of this hybrid sorbent is that, like other amine-based sorbents, it can be easily thermally desorbed at temperatures below 90°C.

Thermal Desorption of the Sorbent

Thermal desorption is used to release the CO₂ that has been captured by the sorbent material.

The sorbent material is heated to a certain temperature, which causes the CO₂ to be desorbed or released from the sorbent and into the gas phase.

Once the CO₂ is released, it can be collected and stored or used for other purposes, such as enhanced oil recovery or industrial processes.

Thermal desorption is an important step in the DAC process as it allows for the regeneration of the sorbent material, which can be reused to capture more CO₂ from the atmosphere.

Carbon Sequestration – Capturing & Storing Carbon

Sequestration refers to the process of capturing and storing carbon dioxide (CO₂) in order to reduce the concentration of greenhouse gases in the atmosphere and mitigate the impacts of climate change.

Carbon sequestration can be achieved through a variety of methods, including geological storage, ocean storage, and biological storage.

Geological storage involves injecting CO₂ into deep underground formations, while ocean storage involves dissolving CO₂ in the ocean.

Biological storage involves the use of plants and other natural systems to capture and store carbon, such as afforestation and reforestation, as well as soil carbon sequestration through sustainable agricultural practices.

Dual Mode Regeneration of the Hybrid Solvent

The researchers in the study, have validated seawater as a viable regenerant for the sorbent.

This means that when the sorbent is desorbed, the CO₂ is simultaneously sequestered as chemically stable alkalinity (NaHCO₃), which is harmless.

Regenerant is a substance or process used to restore the capacity of the sorbent material used to capture carbon dioxide (CO₂) from the atmosphere.

During the CO₂ capture process, the sorbent material binds to CO₂ molecules and becomes saturated over time.

To restore the capacity of the material, a regenerant is used to release the CO₂ molecules from the sorbent, allowing it to be used again for further CO₂ capture.

The dual-mode regeneration of the hybrid sorbent simultaneously desorbs CO₂ and captures it as chemically stable alkalinity in seawater, offering a unique and flexible way to use oceans as sinks for decarbonization.

Benefits of Using Seawater as Regenrant

Using seawater as a regenerant expands the potential applications of DAC technology beyond just land-based installations.

This is particularly important given the limited availability of land suitable for DAC installations in many parts of the world.

The use of seawater as a regenerant also has several advantages:

• Seawater is abundant and readily available in many parts of the world, which makes it an attractive and cost-effective option for DAC installations.
• CO2 that is released during desorption is captured in the form of alkalinity in the seawater, which is a chemically stable and harmless substance.
• This eliminates the need for expensive and complex CO₂ storage systems, which are required for other DAC technologies.

Furthermore, the use of oceans as sinks for decarbonization has several additional benefits.

Oceans are capable of storing vast amounts of CO₂, and the process of sequestration can also have positive effects on ocean ecosystems.

For example, the sequestration of CO₂ in the form of alkalinity can help to buffer ocean acidification, which is a major threat to marine biodiversity.

Hurdles for the Direct Air Capture Technology

There are several primary hurdles that need to be overcome to implement DAC (direct air capture) technology on a large scale primarily, high costs, high energy requirements, technological limitations, low concentration of CO₂ in the air, and more.

The new research upgrades the Direct Air Capture Technology to better deal with the low concentration of CO₂ in the air using the newly developed polyamine-Cu(II) complex hybrid solvent and also provides various other economic opportunities.

While progress has been made in addressing these challenges, large-scale implementation of DAC technology is still likely to take time and will require continued innovation and investment from governments, industry, and other stakeholders.

Nevertheless, the potential benefits of DAC technology in achieving net-zero greenhouse gas emissions make it an important area of research and development for addressing the urgent challenge of climate change.

Conclusion

The development of this hybrid sorbent is an important step forward in the field of DAC, as it provides a more efficient and flexible solution for capturing CO₂ from the atmosphere.

Using seawater as a regenerant offers great economical opportunities for applications of DAC technology beyond just land-based installations, which is critical in achieving our climate goals.

This research strengthens humanity’s hope in tackling the climate change crisis.

References

1. Hao Chen, Hang Dong, Zhongyu Shi, and Arup K. Sengupta, ‘Direct air capture (DAC) and sequestration of CO₂: Dramatic effect of coordinated Cu(II) onto a chelating weak base ion exchanger‘, Science.org(Science Advances), 8 March 2023[↩]
2. Hao Chen, Hang Dong, Zhongyu Shi, and Arup K. Sengupta, ‘Direct air capture (DAC) and sequestration of CO₂: Dramatic effect of coordinated Cu(II) onto a chelating weak base ion exchanger‘, Science.org(Science Advances), 8 March 2023, “Here, we present a Lewis acid-base interaction–derived hybrid sorbent with polyamine-Cu(II) complex enabling over 5.0 mol of CO₂ capture/kg sorbent, nearly two to three times greater capacity than most of the DAC sorbents reported to date.”[↩]