Given the current state on climate change, excessive amounts of CO₂ are present in the atmosphere. As a result, the idea of closing the carbon cycle by using CO₂ as a feedstock rather than a waste material is seen as a promising strategy to both mitigate climate impacts and provide an abundant resource for industrial applications. In this context, plasma-based technologies offer an interesting approach for converting CO₂ into industrial valuable products such as CO, which serves as building block in numerous chemical processes.

 

 

Why add a carbon bed?

 

In practice, efficient conversion of CO₂ into valuable CO molecules, using plasma technology, presents several challenges. One of the key challenges are recombination processes that take place in the plasma’s effluent, in which the converted CO molecules and atomic oxygen recombine to form CO₂. These backreactions are primarily driven by the high collisional frequencies, inherent to plasma systems at atmospheric pressure. In order to mitigate these back reactions, one could try to fully remove oxygen from the system, thereby enhancing CO production. Based on prior research conducted on the topic^1,2,3, solid carbon pellets – placed in a so-called carbon bed – have proven to be an effective scavenger of these oxygen atoms. However, no research to date has investigated the use of a carbon bed in combination with a pure CO₂ microwave plasma. The Effitorch project, therefore, wants to take the opportunity to fill this gap by examining the integration of a carbon bed into a microwave-driven CO₂ plasma system. The choice of carbon as scavenger material has two additional benefits: first, the reaction between the carbon pellets and free oxygen atoms forms additional CO molecules, thus improving the overall conversion. Second, the elevated temperatures in the plasma’s effluent facilitate the reverse Boudouard reaction (CO₂ + C à 2CO), which further increases CO yield.

 

 

Future perspectives in Effitorch:

 

The use of a carbon bed only presents a first step in our experimental campaign within the Effitorch project. Ultimately, the project aims to combine a CO₂ plasma with bio-oil to produce syngas – a mixture of CO and H₂. The idea behind using bio-oil is twofold: analogously to the carbon pellets, it can operate as an oxygen scavenger, hence reducing back reactions; additionally, bio-oil provides a potential hydrogen source for the formation of H₂. However, before proceeding to experiments with bio-oil, an intermediate testing phase will be conducted using ethyl decanoate as a model compound. This intermediate step provides a controlled environment to examine the primary plasma–oil reaction pathways, serving as a benchmark for future experiments with complex bio-oils.

 

Author: Hugo Vallet

 

 

References

 

[1] Girard-Sahun, F., Biondo, O., Trenchev, G., van Rooij, G., & Bogaerts, A. (2022).
Carbon bed post-plasma to enhance the CO₂ conversion and remove O₂ from the product stream. Chemical Engineering Journal, 442, 136268.

[2] O’Modhrain, C., Gorbanev, Y., & Bogaerts, A. (2025).
Post-plasma carbon bed design for CO₂ conversion: Does size and insulation matter? Journal of Energy Chemistry, 104, 312–323.

[3] Biondo, O., Wang, K., Zhang, H., & Bogaerts, A. (2025).
Coupling a CO₂ plasma with a carbon bed: The closer the better. Chemical Engineering Journal, 507, 160190.

 

 

Links

 

https://doi.org/10.1016/j.cej.2022.136268

https://doi.org/10.1016/j.jechem.2024.12.066

https://doi.org/10.1016/j.cej.2025.160190

 

Keywords

 

Carbon bed, CO, conversion, bio-oil