CO₂ utilization: new technologies for converting CO₂ and why GIG Karasek opts for electrochemical reduction

The use of technologies for CO₂ utilization has gained a great deal of attention around the world over the past few years. In the long term, they will be an indispensable component for future economic activity. In this article we show different CO₂ conversion and utilization pathways and explain why GIG Karasek is pushing electrochemical CO₂ conversion in various research projects.

1. Why GIG Karasek is focusing on CO2 utilization

Carbon capture and utilization (CCU) refers to technologies that capture CO₂ from the atmosphere or flue gases and subsequently convert it into value-added products such as plastics, building materials, synthetic fuels or chemicals (e.g. carbon monoxide, methanol, ethanol, olefins, formic acid). How long the CO₂ remains bound by these uses depends on the product. 

CCU technologies are essentially based on two steps isolated from each other: the separation step and the conversion step. Although the overall efficiency of the CCU process depends on the combination of these steps, CO₂ capture and utilization have so far mostly been researched independently of one another. This circumstance has led to the fact that separation systems have already been developed on an industrial scale, while utilization or conversion technologies are still at various stages of development. 

GIG Karasek therefore does not focus its research projects on CO₂ capture, but on the development of innovative processes for CO₂ utilization. The main focus here is on electrochemical CO₂ conversion, which we will discuss in more detail below after presenting currently researched conversion pathways. 

Figure 1: CO₂ capture from point sources and subsequent utilization of CO₂ via various conversion pathways (self-representation).

2. CO₂ utilization: conversion pathways and their technological maturity

Since CO₂ is a thermodynamically stable compound, the conversion of CO₂ usually takes place through a catalytic process with additional input, e.g. from renewable energy sources. Below is an overview of the main recycling technologies currently under investigation, including their technological readiness level (TRL):

2.1.  Thermochemical CO₂ conversion (TRL 5–9)

Thermochemical CO₂ conversion uses catalysts and a combination of heat and pressure to convert CO₂ into valuable products. With a technology readiness level between 5 and 9, this is currently the most mature technology for CO₂ conversion. Challenges with this reaction pathway include reversibility and thermodynamic limitations of reactions. 

2.2. CO₂ mineralisation (TRL 4–8 concrete ingredients, TRL 7–8 concrete curing)

CO₂ mineralisation processes are based on the reaction of metal cations (e.g. Mg, Ca, Fe) with CO₂ to form solid and stable carbonate minerals and thus permanently store CO₂. The resulting carbonates are potentially versatile, for example as fillers, cement additives or for land reclamation projects. CO₂ mineralisation will nevertheless continue to make only a small contribution towards the decarbonisation of industry; it will not be able to offset the CO₂ balance sheet on its own.

2.3. Electrochemical CO₂ conversion (TRL 4–8 C1 products, TRL 1–3 C2+ products)

Plasma catalysis technology is another novel approach to CO₂ utilization. In this process, a weakly ionised plasma, which is very reactive, is generated by supplying electricity. The conversion of CO₂ into basic chemicals, such as methanol and ethylene, is activated by free electrons contained in the plasma. However, plasma chemistry is very complex and a better understanding of plasma reactions and interactions between the plasma and catalyst is needed.

Table 3: CO₂ conversion technologies, including the technical readiness level (TRL), prepared according to ¹.

3. Electrochemical CO₂ conversion as the way forward

From the range of utilization methods presented, the electrocatalytic or electrochemical conversion of CO₂ (eCO₂R) is gaining increasing interest in the scientific community. The following factors in particular are key to this:  

1. One-step conversion: The process enables the one-step conversion of CO₂ into C₁, C₂ and even C₂+ products (complex hydrocarbons). The electrochemical reduction of CO₂ thus also produces products containing two or more carbon atoms per molecule (e.g. ethanol CH₃-CH₂-OH) in just one conversion step.
2. Range of products: The electrochemical process therefore potentially allows the production of a wide range of products.
3. More flexible use of electricity:  Surplus renewable energy can be stored in the form of chemical energy and used again when needed. This enables a more flexible use of electricity (i.e. demand-side management).

Compared to other technologies, electrochemical CO₂ reduction offers a number of significant advantages, which are discussed in more detail below.

4. Electrochemical CO₂ conversion in comparison

Electrochemical reduction is an attractive technology because it can be carried out under mild conditions (near room temperature and ambient pressure) in aqueous solutions, using water instead of molecular hydrogen (H₂) as the hydrogen source. Furthermore, electrochemical conversions are more attractive than other recovery technologies for several reasons, both in terms of energy efficiency and cost:

Figure 2: Advantages of electrochemical CO₂ conversion (self-representation).

The previously mentioned alternative CO₂ utilization technologies have some disadvantages compared to electrocatalytic conversion, which make them less attractive from GIG Karasek's point of view: ²

1. Thermochemical CO₂ conversion requires high pressure and high temperatures, which results in corresponding costs. The method is also not sustainable due to the use of a non-renewable energy source. 
2. The main disadvantage of the bioelectrocatalytic process is its high cost. Currently, biological methanation is even more expensive than thermochemical methanation, which is very cost-intensive anyway. 
3. The photocatalytic process is not possible for large-scale implementation and night-time operation due to the lack of solar radiation. The process is also less user-friendly and product isolation and separation is comparatively difficult.
4. Plasma catalysis technology as another novel process is physically very complex and requires more research to fully understand the process. 

For the reasons given, GIG Karasek relies on electrochemical CO₂ conversion as a recycling technology. Below we provide a brief insight into the strategy pursued by GIG Karasek on this path.

5. Focus on formic acid and carbon monoxide

As already mentioned, electricity is applied in the electrochemical conversion of CO₂ in order to use CO₂ as a raw material for chemical syntheses. Depending on the catalyst materialused, the reaction pathway, the amount of CO₂ feedstock and the energy, there are a variety of eCO₂R products that can be produced.

GIG Karasek has selected formic acid (HCOOH) and carbon monoxide (CO) as two of the most promising products for the application of CCU technology:

• Formic acid is a bulk chemical that is of great interest for energy storage (formic acid fuel cells) and as a base material for the chemical industry.
• Carbon monoxide can be used in combination with hydrogen (H₂) to produce synthesis gas and as a chemical base material. 

Furthermore, CO and formic acid record the highest market price per electron used, although the market price is lower than for other products such as methanol and ethanol. They are therefore good candidates for the development of CCU technologies.

Table 4: Electrochemical CO₂R products adapted from ³.

6.Innovative research project: direct electrolysis of CO₂

GIG Karasek is currently involved in several research projects dealing with innovative approaches to the electrochemical conversion of CO₂ into valuable materials. We have already presented the research cooperation with the Johannes Kepler University Linz (JKU Linz) on CO₂ utilization based on the so-called "Dream Reaction". 

As part of another project for the direct electrolysis of CO₂, GIG Karasek is developing an expanded CCU system based on a new type of electrolysis cell in cooperation with three companies from Upper Austrian and the University of Innsbruck. 

The aim of the project is to optimise the energy/cost ratio of CO₂ capture and utilization of flue gases by means of direct CO₂ electrolysis, by eliminating intermediate steps such as thermal desorption and product separation or processing. The capture and electrochemical conversion of CO₂ thus no longer takes place in two separate steps, but is integrated into one unit.

The innovative technology is based on a symbiotic CO₂ absorption and electrolysis cell that significantly streamlines the process and increases energy efficiency. This mini-plant system serves as the basis for the next scale-up steps for industrial research with the aim of establishing CO₂ utilization as a future business sector and taking an innovative step in waste gas purification. 

GIG Karasek contributes its expertise in industrial plant construction with regard to separation technology and cell periphery construction with its production sites in Attnang-Puchheim and Gloggnitz and a planning office in Graz.

Figure 3: In direct electrolysis, CO₂ capture and conversion to valuable products takes place in just one step. Ideally, the process is fed from renewable energy sources (self-representation).

7. Challenges in electrochemical CO₂ reduction in industry

The economic feasibility of CCU concepts depends not only on technological readiness, but also on the creation of political framework conditions. These include, in particular, carbon tax policies, government support for technology development, and incentives for environmentally friendly production pathways.

Industrial eCO₂R is not yet competitive compared to fossil fuel alternatives for the chemical industry and energy storage. However, as soon as the electrical energy required for conversion can be fed from renewable energy sources, competitive production is possible. This is especially true in view of enormously rising prices for energy from fossil sources.

Of course, the electrification of the chemical industry is a challenging path in terms of economic competitiveness with industries based on fossil fuels or non-electrochemical pathways. Nevertheless, GIG Karasek is convinced that the development of large-scale electrochemical technologies (e.g. eCO₂R) that run on emission-free electricity is necessary in the future, given the enormous environmental impact and the unavoidable CO₂ emission costs.

Figure 4: CCU technologies in the context of a sustainable chemical industry, adapted according to © nova-institute.eu.

9. Conclusion: CO₂ utilization as a new business sector

CO₂ can be made usable as a raw material in the medium term through innovative technologies; for example, for plastics, building materials or fuels. Decisive advantages for CO₂ utilization as a future business sector are offered by technologies that can use electrical energy generated from renewables directly for CO₂ conversion. Electrochemical CO₂ conversion at moderate process temperatures is a particularly efficient and environmentally friendly method for this. Research and development of this CO₂ conversion pathway must therefore take place now in order to be prepared for the future.

Find out more about why investing in this market can make sense right now in our article “CO₂-Utilization: 5 reasons why companies should participate now".

¹ Nishikawa, E. (29 April 2022). CO2 conversion & utilization pathways: Techno-economic insights. PreScouter. https://www.prescouter.com/2022/04/co2-conversion-utilization-pathways/ (last accessed 27/09/2022)

² Samanta, S., & Srivastava, R. (2020). Catalytic conversion of CO2 to chemicals and fuels: the collective thermocatalytic/photocatalytic/electrocatalytic approach with graphitic carbon nitride. Materials Advances, 1(6), 1506–1545. https://doi.org/10.1039/d0ma00293c

³ Mohsin et al., Economic and Environmental Assessment of Integrated Carbon Capture and Utilization, Cell Reports Physical Science (2020), https://doi.org/10.1016/j.xcrp.2020.100104

⁴ CO₂: Raw material instead of pollutant. Cleantech-cluster.at. https://www.cleantech-cluster.at/news-presse/detail/news/co2-rohstoff-statt-schadstoff (last accessed 27/09/2022)

⁵ Steeg, D., Renewable energy and renewable carbon for a sustainable future − graphic. Renewable Carbon Publications. Last accessed 18 October 2022, from https://renewable-carbon.eu/publications/product/renewable-energy-and-renewable-carbon-for-a-sustainable-future-%e2%88%92-graphic/