Scientists speed up carbon dioxide capture with enzymes

Climate change is accelerating, driven by rising CO₂ levels that warm the planet and intensify extreme weather. Even if new emissions are eliminated, excess CO₂ will remain in the atmosphere for centuries, fuelling the crisis. To counter this, researchers are developing the direct air capture (DAC) technology, which removes CO₂ directly from the air. However, because atmospheric CO₂ is extremely diluted, capturing it is slow, expensive and energy-intensive. Existing methods either use too much energy or require massive infrastructure. To overcome these barriers, scientists are exploring nature’s own solutions – specifically, enzymes that speed up CO₂ absorption while reducing the energy required.

“Our key discovery is that enzyme-assisted DAC can match the speed of hydroxide-based systems without the extreme energy costs. Potassium carbonate is already a more sustainable alternative, but it is too slow on its own. The enzyme solves this, enabling rapid CO₂ absorption without requiring high heat to release it. This means that enzyme-assisted DAC could be both scalable and cost-effective, offering a realistic pathway for removing CO₂ from the atmosphere. The next step? Scaling up from laboratory tests to real-world systems – ensuring enzyme stability, optimising costs and integrating the technology into industrial processes,” explains one main author, Peter Westh, Professor, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby.

CO₂ DAC beyond smokestacks

DAC is an emerging technology designed to remove CO₂ directly from the atmosphere. Unlike traditional carbon capture methods that target emissions from power plants or industrial sites, DAC addresses past emissions, actively reducing atmospheric CO₂ levels. However, because CO₂ in the air is highly diluted – just 0.04% of the atmosphere – capturing it efficiently and cost-effectively is a major challenge.

“The main hurdle is that traditional capture methods work well when CO₂ is concentrated, but pulling it from the air, where it is highly diluted, is much slower and more expensive.” says Peter Westh.

One approach to capturing CO₂ relies on chemicals that react with it, such as hydroxides and carbonates. A major breakthrough in this field has been using carbonic anhydrase, a naturally occurring enzyme that accelerates the reaction between CO₂ and water in living organisms. Scientists are now engineering this enzyme to speed up CO₂ capture in industrial settings, potentially making DAC more viable.

“Carbonic anhydrase is an enzyme that speeds up CO₂ absorption. It works really well for capturing CO₂ from such places as power plants or cement factories, where CO₂ is highly concentrated. This makes the process more rapid, so the equipment can be smaller and cost-effective ” notes another main author, Agnese Zaghini, PhD Student, Department of Biotechnology and Biomedicine, Technical University of Denmark.

Rapid but energy-intensive

Currently, the fastest way to capture CO₂ is by using a highly reactive chemical called concentrated hydroxide (such as sodium or potassium hydroxide). Hydroxide solutions instantly absorb CO₂ from the air, which makes them highly effective. However, the downside is that extracting the captured CO₂ requires extreme heat (requiring 7–9 GJ per tonne of CO₂), making it expensive and energy-intensive. This has raised concerns about whether DAC using hydroxide is truly sustainable at scale.

“Right now, the fastest way to capture CO₂ is using concentrated hydroxide, which absorbs CO₂ almost instantaneously. However, the significant energy required to release the captured CO₂, about USD 150 to USD 200 per tonne, makes this method costly and raises sustainability concerns,” points out Peter Westh.

Because current methods require considerable energy, researchers are investigating alternative sorbents such as potassium carbonate (K₂CO₃). Although it absorbs CO₂ more slowly than hydroxide, potassium carbonate is a more sustainable option because it requires much less energy to regenerate.

“This trade-off between speed and energy efficiency has been one of the biggest bottlenecks in DAC development. This is where enzymes such as carbonic anhydrase offer a promising solution,” remarks co-author Silke Flindt Badino, Research Specialist, Department of Biotechnology and Biomedicine, Technical University of Denmark.

A boost from nature

By dramatically increasing the speed of the CO₂ absorption reaction, carbonic anhydrase could enable potassium carbonate to work as rapidly as hydroxide – without the extreme energy costs.

“Some early research suggests that enzyme-assisted DAC could match the kinetics of hydroxide-based systems while maintaining lower energy requirements. To evaluate enzyme-assisted DAC, we used a laboratory-scale absorption column designed to mimic industrial conditions,” explains Silke Flindt Badino.

The set-up for enzyme-assisted DAC used potassium carbonate as the sorbent and carbonic anhydrase as the catalyst. This set-up was crucial for ensuring that the enzyme could function effectively even under the low CO₂ concentrations typical of DAC.

“The enzyme we use is highly stable, even in extreme conditions. It comes from a deep-sea bacterium called Persephonella marina, which thrives in boiling-hot hydrothermal vents. That makes it a great candidate for industrial use,” adds Agnese Zaghini.

Testing in the laboratory

The experimental set-up was a packed-column system in which air with an ambient CO₂ content was circulated through a liquid sorbent flowing in the opposite direction, designed to maximise surface area and enhance gas–liquid contact.

“To test enzyme-assisted capture, we developed a laboratory-scale column packed with tiny glass beads, simulating real industrial conditions. We pumped air through a liquid sorbent and observed the reaction rates when the enzyme was introduced,” explains Agnese Zaghini.

To assess the enzyme’s effectiveness, the researchers controlled key operating parameters, including liquid flow rate, gas composition and enzyme concentration. One critical test involved keeping the liquid flow rate constant while varying the gas flow rate. This helped to determine whether the enzyme could maintain its effectiveness even as airflow increased – a crucial factor for scaling up the process.

“We kept the liquid flow steady at 25 mL per minute and tested different gas flow speeds. That experiment was key – it showed that as we pushed air through more rapidly, the enzyme still kept up, proving its efficiency under real-world conditions,” says Agnese Zaghini.

From prototype to reality

Creating the DAC system posed unique challenges, since off-the-shelf solutions were inadequate. The researchers had to design and fine-tune the absorption column to accurately assess the specific contributions of the enzyme in CO₂ DAC.

“Constructing the column was not straightforward; it required custom design and meticulous adjustment to ensure that we were evaluating the enzyme’s effects accurately and not just the sorbent’s natural absorption capabilities,” explains Agnese Zaghini.

By carefully controlling experimental conditions and varying gas flow rates, they quantified the enzyme’s impact, demonstrating that it significantly enhanced the efficiency of potassium carbonate systems for CO₂ capture.

“Using potassium carbonate instead of hydroxide is a great way to lower energy costs because it does not require extreme heat to release the captured CO₂. But it more slowly absorbs CO₂, which requires bigger and more expensive equipment. Our key discovery? Adding an enzyme speeds up the process, solving both the energy and speed problems,” highlights Peter Westh.

Finding the right balance

Further analysis showed that enzyme-assisted DAC optimally balanced reaction speed and energy efficiency. The enzyme compensated for the slow absorption rate of potassium carbonate, and potassium carbonate itself avoided the high energy requirements of hydroxide regeneration. This suggests that enzyme-assisted systems could match the efficiency of hydroxide-based DAC without the extreme costs associated with heat regeneration.

“We found a sweet spot: enzymes fix the slow speed of potassium carbonate, and potassium carbonate eliminates the high energy hydroxide requires. This means that enzyme-assisted DAC could match the efficiency of hydroxide-based systems but at a much lower energy cost,” concludes Peter Westh.

Scaling up enzyme production affordably remains a pivotal concern.

“One of the greatest challenges in DAC is handling the massive amounts of air needed to capture CO₂. We found that as airflow increases, the enzyme becomes even more effective. It does not get overwhelmed, which is a big deal for scaling up,” observes Silke Flindt Badino.

Scaling presents challenges

These findings suggest that enzyme-assisted DAC may offer a scalable, energy-efficient alternative to conventional high-energy CO₂ capture methods. Although these systems accelerate CO₂ absorption, their main hurdle is CO₂ release – typically achieved through energy-intensive high temperatures in traditional systems. For scalability, the enzyme must operate effectively under such harsh conditions without degrading.

“One major hurdle in making this enzyme practical for industry is that capturing CO₂ is just step one. The second step – releasing the CO₂ so it can be stored or used – usually requires high heat. For this to work at scale, we need to ensure that the enzyme can handle these extreme conditions,” explains Silke Flindt Badino.

Although several companies are already mass-producing enzymes for industrial use, the feasibility of ramping up production to meet DAC demands still presents economic uncertainties.

“The economic viability of mass-producing the enzyme for DAC is not yet fully understood. Although some companies have the capability for mass production and others are progressing towards full-scale carbon capture systems, precise cost details remain elusive. However, indications suggest that we are nearing a point at which commercial viability is achievable,” says Peter Westh.

Cost matters, but so does longevity

Considering cost–effectiveness, enzyme-assisted capture is already competitive for point-source applications, such as power plants. In these environments, CO₂ concentrations are much higher, making capture less expensive and more efficient. However, in DAC, with extremely low CO₂ levels, costs naturally increase. Stability studies indicate that some enzymes can last for about a month before being replaced, which suggests that enzyme-based DAC could still be cost-effective in the long term.

“For point-source capture, such as power plants, CO₂ capture is already competitive at less than USD 100 per tonne of CO₂. DAC is naturally more expensive because CO₂ is so diluted. But enzyme stability studies suggest that DAC could still be cost-effective, since the best enzymes last about a month before being replaced,” points out Peter Westh.

Ultimately, although enzyme-assisted DAC offers a promising pathway toward more efficiency, further research is needed to optimise enzyme stability, reduce production costs and integrate the system into large-scale industrial processes.

“The laboratory-scale experiments demonstrated that enzyme-assisted DAC can work efficiently, but the next crucial step is scaling up the technology for real-world applications,” remarks Silke Flindt Badino.

Moving from small laboratory set-ups to large-scale industrial systems requires testing the enzyme under higher gas flow rates, varying environmental conditions and longer operational periods. Collaboration with teams that already have full-scale capture set-ups would be key to understanding how the enzyme performs outside controlled laboratory conditions.

“The next big step is scaling up. We have proven the concept in the laboratory, but real-world systems are much bigger. It would be amazing to collaborate with a team that already has large-scale DAC set-ups and test whether our enzyme works at that level,” says Agnese Zaghini.

From laboratory to industry

One great technical challenge is handling the sheer volume of air to be processed in a real DAC system. The laboratory tests used only 50 millilitres of liquid, but industrial-scale systems must be capable of processing thousands of cubic metres of air continuously. Pilot-scale testing in specialised facilities will be essential to determine whether the enzyme can perform consistently and efficiently under real industrial conditions.

“Our laboratory experiments used only small quantities – around 50 millilitres. However, transitioning to an industrial scale would involve processing thousands of cubic metres of air. Pilot-scale testing, especially using Denmark’s advanced facilities, is essential to bridge this significant scale-up gap,” explains Peter Westh.

To move forward, securing funding and industrial partnerships is a priority. The researchers are already discussing with potential collaborators but still need the necessary resources to bring enzyme-assisted DAC to larger-scale testing. Working with existing carbon capture teams will help to integrate this method into real-world applications and refine the approach for commercial viability.

“Discussions are underway with potential partners, and we are actively seeking funding. Our next strategic move involves partnering with teams equipped with the necessary infrastructure to rigorously test our system in real-world conditions,” states Peter Westh.

Making enzymes work smarter

Another important focus for future research is optimising enzyme application. Right now, the enzyme is dissolved in the liquid sorbent, which means that a large quantity is needed to maintain efficiency. If the enzyme could be immobilised on a solid surface or made more efficient, the process could use less enzyme while maintaining or even improving performance.

“Maybe the next step should be improving how the enzyme is used. Right now, it is floating in the solution, but this requires a lot of enzyme. We are therefore currently working on enzyme engineering and new ways to make the process more effective so we can use less enzyme while still getting the same boost in CO₂ capture,” suggests Agnese Zaghini.

As enzyme-assisted DAC technology advances, clear and effective communication will be essential for scientific and industry adoption. The researchers recognise that technical details matter, but making the findings accessible and easy to understand for various stakeholders is equally important – including policy-makers, industry leaders and the general public.

“We will provide all the feedback we can. We understand the balance – too technical, and people get lost; just right, and our research advances. With ongoing research, pilot testing and industry collaboration, enzyme-assisted DAC can evolve into a scalable, cost-effective method to reduce atmospheric CO₂,” concludes Peter Westh.