Associate Professor Philip L. Fosbøl and Postdoc Humbul Suleman. Photo by Christian Ove Carlsson.

A greener version of carbon capture

Tuesday 29 Sep 20
|
by Morten Andersen

Contact

Philip Loldrup Fosbøl
Associate Professor
DTU Chemical Engineering
+45 45 25 28 68

Contact

Nicolas von Solms
Professor
DTU Chemical Engineering
+45 45 25 28 67
Lowering CO2 emissions is no longer considered enough to preserve the Earth’s climate. We also need to actively capture CO2.

According to the IPCC (the International Panel on Climate Change), the world will need not only to get to zero carbon net emissions by 2050. If we are to preserve the present climate, we even need to achieve negative emissions.

“Saying negative emissions is another way of saying Carbon Capture and Storage (CCS),” says Associate Professor Philip L. Fosbøl, AT CERE, DTU Chemical Engineering.

“Even with a full transition to renewable energy, we will still need to produce goods which are bound to emission of CO2. We cannot just stop using steel, cement, medicine, paper, and similar types of welfare goods which all rely on processes that emit a noticeable amount of CO2. Therefore, we will not be able to do without carbon capture. In other words, we should invest in CCS just like we invest in renewable energy technologies,” he continues.

DTU Chemical Engineering has pursued CCS consistently, regardless of changes in political interest over the years. Not least has participation in all major EU programmes over the last two decades allowed a high level of activity in the field.

Enzyme from blood to the rescue

A major challenge in CCS is reducing the energy consumption required for capturing the CO2. A high energy consumption will both be damaging to the sustainability of the method and to the economic feasibility. Therefore, it is good news that the researchers at DTU Chemical Engineering have found a method which improves current state-ofthe- art capture methods when it comes to energy efficiency.

The new method is based on addition of the enzyme CA (carbonic anhydrase). CA is found in human blood. In our body, the main function of CA is to enhance the mass transfer of CO2 in our lungs by catalysing the reversible hydration of CO2.

“CA is one of the fastest enzymes known. This is highly attractive in relation to carbon capture, as we typically need to capture CO2 from huge amounts of flue gas. We have shown that CA is able to speed up CO2 capture in an industrial context. While the enzyme isn’t a CO2 solvent in itself, it increases the capture capacity of the best commercially available solvents,” explains Associate Professor Nicolas von Solms, also working in AT CERE.

The industrial state-of-the-art solvents for CO2 capture are amines such as MDEA (methyldiethanolamine).

“MDEA is a very efficient and specific solvent for CO2 capture, but it is rather slow. You can compensate for this by increasing the size of your capture plant, but that would add to both building costs and energy consumption. The latter is problematic both in terms of operating costs and sustainability. By speeding up the capture process, we can operate a smaller facility.”

 

A green additive

In terms of economic feasibility, the new method is currently not superior, because the cost of the CA needs to be factored in. Even though the enzyme is not consumed directly in the process—enzymes function like catalysts in an industrial plant, they facilitate the reactions between other compounds – some new CA needs to be added to keep the process going. The price of the enzyme will go down if and when more capture facilities adapt the method, allowing CA to be produced with economy of scale. Still, for some time the cost of the enzyme will imply that the new, more efficient process will have overall costs that roughly equal those of current CO2 capture by amines without enzymes added.

“So initially, the advantage will not be economical, but by operating smaller and more energy-efficient plants, carbon capture becomes more sustainable. On top of that we’re using a green additive, since enzymes are manufactured at biotechnological plants under mild conditions,” Nicolas von Solms points out.

Experiments and modelling proving the efficiency of the CA-based method have mainly been carried out by Arne Gladis in his PhD project at DTU Chemical Engineering. Arne Gladis was supported by an EU grant through the INTERACT project which also included Professor John Woodley (PROSYS research centre), and after completing his PhD degree, Arne Gladis is now with Wacker Chemie, Germany. The efforts are continued by Postdoc Humbul Suleman, supported by a Eurotech scholarship. Supervisors in both contexts are Associate Professors Nicolas von Solms and Philip L. Fosbøl. The efforts are carried out in collaboration with Novozymes, world leading supplier of industrial enzymes.


Carbon Capture at DTU Chemical Engineering

Some 8-9 researchers and a similar number of students are doing projects on carbon capture at DTU Chemical Engineering. The efforts are anchored in AT CERE (Applied Thermodynamics, Center for Energy Resources Engineering).

Fundamental research projects on the subject include the use of ionic liquids (ILs) as solvents for carbon capture, and swapping CO2 for methane in gas hydrates, respectively. Both of these projects are coordinated by Associate Professor Nicolas von Solms.

Further, carbon capture plays a role in three ongoing projects with biogas as the common denominator. In the first project, MeGa-StorRE (Methane Gas Storage for Renewable Energy), methane is produced by removing CO2 from the biogas. In the second project, Bio Re-fuel, CO2 is also removed from the biogas, but instead of methane, the end-product will be methanol. The third project, BioCO2, focuses on utilizing the captured CO2 as a valuable industrial feedstock. All three projects are coordinated by Associate Professor Philip L. Fosbøl. The MeGa-StoRE and Bio Re-fuel projects were originally developed at DTU Mechanical Engineering, still a partner in both projects.

Finally, there has been research on carbonate looping in CHEC research centre with collaboration with FLSmidth & Co. A/S coordinated by Associate Professor Weigang Lin. Carbonate looping is a second-generation carbon capture technology, which is especially suitable for the cement industry, where the raw materials can be reacted reversibly between their carbonate form and their oxide form to separate CO2 from other gases with lower energy penalty.

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