“We need technologies that convert CO2 into valuable materials”

In an interview, Benjamin Dietrich, project manager of the NECOC project, discussed the process of converting CO2 into solid carbon, as well as its applications and challenges.

What is the significance of technologies that filter CO2 from the air and transform it into solid carbon in addressing the issue of climate change?

Dietrich: Technologies like this play an enormous role in combating climate change. Various studies, including those by the IPCC and Climate Protection Science Platform, indicate that achieving the climate protection goal requires more than just reducing emissions from current systems and processes and transitioning to electric transportation. It is also essential to remove CO2 from the atmosphere in a deliberate manner and store it permanently in a climate-safe way, which is known as creating negative emissions.

What are the methods to achieve negative emissions?

One way to achieve negative emissions is through the classic CCS process where CO2 is compressed underground or under the sea, which removes CO2 from the atmosphere for the long term. However, this method results in the CO2 being permanently stored and unavailable for further use. Although CCS is not yet possible in Germany, it is under discussion, and Norway is already practicing it. To achieve a sustainable future, new technologies are needed that use a physical-chemical process to convert CO2 into a valuable material that can replace fossil raw materials. By combining the generation of negative emissions with the production of long-lived recyclables, such processes can make a double contribution to climate protection.

What recyclable material can CO2 be converted into?

For instance, it can be converted into solid carbon powder. The NECOC project, which stands for Negative Carbon Dioxide to Carbon, has developed a technology that combines the steps of CO2 capture, methanation, CO2-free hydrogen production, and pyrolysis to produce such powder from atmospheric CO2. Currently, extensive characterization studies are being conducted to determine the different modifications of carbon that may occur depending on the process conditions in the pyrolysis step. These modifications can be appealing to different recycling sectors.

Where could the carbon obtained in this way be used in the future?

Possible future applications include building materials, paints, batteries (such as lithium-ion batteries for electric vehicles), products for the agricultural and medical sectors, and the polymer industry.

At the beginning of December you put a pilot plant into operation for the first time…

… yes, the components of the process were tested by our project partners and coupled in a system. Climeworks is responsible for the CO2 separation process (Direct Air Capture, DAC), Ineratec for the methanation process, and KIT for the pyrolysis process. Regenerative electrolysis is used to supply hydrogen in the methanation step.

What makes the coupling of the processes so difficult?

Two major challenges confront us. Firstly, each process step necessitates its own particular process conditions such as specific temperature and pressure levels. We, therefore, coordinate the distinct process conditions in the NECOC network, after which we link the processes. Our approach is dependent on particular simulations and design calculations.

What is the second challenge?

Secondly, there is a challenge of dealing with by-products or intermediate products that may arise during the process and need to be introduced into the following step. For instance, any unconverted CO2 in the methanation step may be passed onto the pyrolysis reactor filled with liquid tin, which can potentially impact the process control or properties of the carbon produced, possibly even in a positive way. This aspect requires thorough investigation.

How suitable is the microgranular carbon powder obtained in the process for the production of battery anodes or carbon fibers?

Initially, the project focused on the production of carbon black, which gave the project its name. However, it has been discovered that other forms of carbon can also be produced. Our team is currently carrying out in-depth characterization studies and we have already released some initial findings. Additional results are being worked on and will be published in the first half of 2023. While carbon black may not be suitable for use in lithium-ion batteries, other forms of carbon can be produced by adjusting the process parameters during the pyrolysis step.

Should industries that are expected to emit significant amounts of CO2 in the medium term be particularly interested in this research?

Yes, that is correct. The technology can be utilized not only to filter CO2 from the air but also from other point sources of CO2. This is particularly relevant for industries such as cement production that cannot eliminate CO2 emissions entirely. The technology will likely become more appealing in these industries as CO2 taxes increase or CO2 certificates become more expensive. Additionally, it is possible to simultaneously filter CO2 from the air and from other point sources, creating a mixture of the two streams for methanation. This could improve the company’s internal emissions balance.

That could encourage carbon-intensive industries to shift down a gear when it comes to cutting emissions…

Our priority is to achieve negative emissions and produce non-fossil carbon, rather than allowing companies to rely solely on such technologies to avoid reducing their CO2 emissions through other means.

How is the process planned to be brought towards industrial application?

Initially, we conduct a comprehensive characterization of the carbon produced. Based on this, we draw reliable conclusions about the process conditions that lead to specific modifications and qualities of the carbon. We then conduct targeted experiments to investigate the impact of accompanying components in the process, such as how unconverted CO2 in the methanation step affects both the process and the carbon.

After the characterization and accompanying experiments, our focus shifts towards the energetic optimization of the process through simulations before scaling up. We will examine various material and design aspects that contribute to increasing the throughput in pyrolysis.

How much carbon will the process be able to produce in the future?

We are currently in the process of determining the answer to this question. Since the project’s initiation in December 2019, our focus has been primarily on designing and structuring the overall process, as well as creating a roadmap for characterizing the carbon. In December, we were able to successfully operate the integrated system over a longer period of time, and we now have real-world data to analyze. Based on this, we can estimate the amounts of CO2 that can be absorbed and the amount of carbon that can be produced, as well as the potential contribution to climate protection through the associated negative emissions.