Across Europe, the drive toward climate neutrality by 2050 is reshaping industries and energy systems. Alongside the boost for renewables and energy efficiency, the European Commission has identified industrial carbon management (ICM) as a critical pillar of the transition.

Therefore, these ICM technologies are believed to be essential for tackling the hard-to-abate emissions from cement, steel, and chemicals that renewables alone cannot eliminate. However, to ensure the adequate deployment of ICM technologies at EU level, in step with our decarbonisation milestones towards 2050, the EU will need to be ready to capture at least 50 million tonnes (Mt) of CO₂ per year by 2030.

These are raising the stakes on innovation in carbon mitigation.

Against this dynamic backdrop, the REUSE Project: Enzymatic CO₂ Capture in a Rotating Packed Bed and Electrocatalytic CO₂ Reduction to Useful Products – is exploring a novel frontier: combining enzyme-enhanced CO₂ capture with electrocatalytic conversion to transform pollutants to valuable products. We sat down with REUSE Project Coordinator Dr. Athanasios Papadopoulos to discuss how this enzyme-driven approach aligns with, and could benefit from, Europe’s emerging industrial decarbonisation playbook.

1. Goodmorning Dr. Papadopoulos, can you let us know what makes REUSE’s approach to carbon capture different from traditional/current methods?

The REUSE carbon capture approach is very suitable for flue gases that contain low concentrations of CO₂, typically below 15 vol%; therefore, are the most challenging ones for decarbonization. For this reason, we are using a solvent-based capture approach that is suitable for such concentrations. Conventional solvent-based capture systems use columns that are filled with packing material. In industrial settings such columns may have height above 30 meters and diameters of more than 5 meters. These are enormous structures that incur high capital costs, with detrimental effects on the cost of CO₂ capture technologies. In solvent-based CO₂ capture systems, the solvent with the absorbed CO₂ needs to be heated at temperatures of around 120°C to release the CO₂ (for subsequent use or storage) and to regenerate the solvent. This practise results in high operating costs.

In REUSE, the packed columns are replaced by rotating packed beds (RPBs). The intense rotation of the packing material contained in RPBs greatly facilitates the absorption of CO₂ in the solvent. The volume of RPBs is 20 times lower than that of conventional columns, for systems of the same capture efficiency. This technology reduces the capital expenditures, whereas the space footprint of the systems is also considerably lower. The solvent with the captured CO₂ is then transferred directly to the cell that is used for conversion of CO₂ into products.

This approach avoids the thermal regeneration and the desorption column that are typically used in conventional capture processes, with beneficial effects on energy consumption and equipment expenditures. Renewable electricity can be used directly in the conversion cell, whereas the hydrogen needed for the conversion is produced directly into the cell through electrolysis and is not transferred from a separate electrolyzer, with beneficial effects again on equipment expenditures.  

2. How do enzymes and the Rotating Packed Bed actually help capture CO2 more efficiently?

The RPB enables significant increase in the mass transfer rate of CO₂ into the liquid solvent. This allows the capture of CO₂ in smaller equipment than the conventional packed bed columns. The enzyme enhances the capture rate by acting as biocatalyst. When the CO₂ goes through the enzyme, the product of the reaction between CO₂ and water is produced considerably faster compared to having only solvent. The combination of the two (RPB and enzyme) is expected to have added value.

3. What happens to the CO2 once it’s captured – how do you turn it into useful products?

When CO₂ is captured, it is dissolved in a liquid solvent and transferred into an electrocatalytic cell. Unlike water, which is commonly used in conventional systems, solvents can hold much more CO₂. This higher solubility of CO₂ means a greater amount of CO₂ is available for conversion.  The CO₂ encounters a catalyst in the electrocatalytic cell. The catalyst is already deposited on one of the electrodes. The use of electricity enables the electrolysis of water and the production of hydrogen.  It also enhances the driving force for the reaction of CO₂ with hydrogen in the presence of the catalyst. Depending on the used catalyst, it is possible to attain different types of products.

4. Why did you choose formic acid and carbon monoxide as the target products?

In general, the REUSE concept can work to produce any kind of chemical or fuel from the combination of a carbon source and hydrogen. In published literature it has been demonstrated that it is possible to produce methanol, methane, ethylene and other compounds. These are either fuels or intermediate chemicals that are used as raw materials to produce various useful products.

Formic acid and carbon monoxide have high value.

Carbon monoxide is a key component of syngas (the other being hydrogen) that is used in the Fischer-Tropsch process to produce fuels. Formic acid is the simplest organic acid and may be used as a fuel itself or as a chemical that stores hydrogen, among other uses. According to published literature, the electrocatalytic production of formic acid and carbon monoxide can be economically competitive with conventional, e.g. thermocatalytic, methods to produce these materials.    

5. How is the project progressing so far – what have you achieved in the lab or pilot stage?

The project is progressing very well. In the lab, we have developed new catalysts designed to reduce the effects of tar formation in biomass gasification, and these are now being tested. We have also applied advanced statistical methods to evaluate fuel blends for gasification that are able to reduce the production of carbon dioxide.

On the biological side, we have created new enzyme variants that are resilient and stable under the conditions of CO₂ absorption and retain their activity for long periods. Such enzymes have been immobilized onto fibrous material that is well suited for use in RPBs. Testing has resulted in appropriate material geometries that will allow the efficient use of this material in the RPB.

In parallel, we are developing catalysts and substrates to enable the reduction of CO₂. A zero-gap electrocatalytic cell of large electrode surface area has been designed and will be available soon for experiments.

To support these efforts, we have been building AI-enabled models to stimulate key processes and will be used as the backbone for the techno-economic studies that will be performed in the project. Finally, we have begun engaging with industrial stakeholders that may be interested in this technology, sharing the potential advantages of this technology to encourage future adoption.

6. How could these technologies benefit hard-to-abate industries like cement, steel or energy in Europe?

The REUSE technology allows the direct CO₂ capture and conversion into useful products. This is an excellent technology for the energy industry, especially in view of its transformation into one that will be based predominantly on biomass in the future. Biomass combustion systems may enable the decarbonization of various sectors as they allow for highly efficient use of sustainable biomass residues. Among other applications, they will be exceptionally useful to meet industrial energy requirements, especially in cases where high temperatures are needed for industrial operations and may not be easily satisfied using other types of renewable technologies.

The combination of biomass energy sources with carbon capture and utilization may enable the achievement of net-negative emissions. This will help increase the penetration of renewables in energy systems and meet the ambitious goals of the EU for greenhouse gas emission reduction. Industries like cement or steel, other than requiring high temperatures which are achieved with fuels, they also include raw or complementary materials that contain CO₂. In this respect, the implementation of carbon capture will be imperative to remain operational. The REUSE proposal may also enable the generation of products that can offset the costs of capture and add economic value.

7. Looking ahead, what excites you most about the future of enzyme-driven carbon capture?

Enzymes offer a natural medium for CO₂ capture that reduces the use of chemicals. They may also act as biocatalysts for the conversion of CO2 into useful products, and they can reduce the use of previous metals that are often used in electrocatalytic cells. The development of enzymes for such applications is still at a low technology readiness. Significant research efforts are needed to improve their resilience, activity and yield. This is an open field for the collaboration of engineers with biologists and biochemists and there will be significant research opportunities to this end in the future.

This project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement No. 101172954. Views and opinions expressed in this article are however those of the author(s) only and do not necessarily reflect those of the European Union.