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In a small town near Zurich, the company Climeworks operates a pilot plant that fishes and stores 900 tons of CO2 from the air every year. In other words, a system with which the CO2 sins of the past can be made good. However, the resource requirements are considerable. Among other things, 250 liters of water are needed to filter one ton of CO2 out of the air, explains Professor Felix Creutzig from the Mercator Institute for Climate Change Research in Berlin, who carried out a life cycle analysis of direct air capture systems. The efficiency could be increased significantly through renewable energies. The electricity demand of such systems could still be used more sensibly, but in the future, in the second half of this century, such systems could become important.
Very large amounts of CO2 could be filtered out of the air
Ralf Krauter: How do the air filter systems work whose resource consumption you looked at?
Felix Creutzig: These are systems that filter CO2 from the air by binding this CO2 to chemical sorbents. These sorbents are then released again under the action of heat and transported away in a concentrated stream, so to speak, so that they can then be stored somewhere. And the systems differ in which sorbent they take and what temperature is needed to dissolve them from the chemical sorbent, there are high-temperature systems and those that get by with just 100 to 120 degrees.
Krauter: What amounts of CO2 can in principle be filtered out of the air with such devices?
Creutzig: The good thing about this technology is that it is in principle unlimited, which means that we can really, very large amounts of CO2 from the air. The problem is, of course, that it costs and that also requires a certain amount of material. But there are no fundamental limits to what can be filtered.
250 liters of water for one ton of CO2
Krauter: First of all, you have precisely quantified which resources are necessary, for example to filter a ton of CO2 from the air. What do you need for that?
Creutzig: You need different resources, metal, water, and there is also a certain amount of air pollution. To name a few key figures, about 250 liters of water are needed for one ton of CO2. And it is also important that the process requires energy, which also produces some CO2, which is why a ton that is filtered out of the air only comes from 700 to 900 kilograms, depending on how you do it actually going underground.
Krauter: Does that mean the technology is not yet incredibly efficient?
Creutzig: It’s not that efficient, but there is an option to do it much more efficiently. We examined that, and the central option is of course to focus the energy supply primarily on renewable energies with solar and wind energy, as well as to get the heat that is needed, for example from heat pumps, so that efficiency can be increased significantly. That, of course, is one of the desirable goals here.
Electricity requirements can now be used more sensibly
Krauter: Let’s talk about the not very low power requirement, which you can also quantify more precisely for the first time. The sum of 1,000 kilowatt hours per ton of CO2 that is fished out of the air is included in your analysis. Is that a lot or a little compared to other climate protection measures?
Creutzig: This is very much. So that’s the big problem with this technology, otherwise it sounds wonderful. It has a very high demand for electricity, and here I would also say that this technology should not use this electricity now, it is much more sensible to use heat pumps in buildings, for example, to electrify the transport area, so we would need the additional one now Electricity we produce. But: If we have actually carried out these measures in 2040 with the normal, in quotation marks, climate protection measures, then we can also use electricity through, for example, photovoltaics and wind to use air capture systems.
“A possibility in the second half of the century”
Krauter: So if we look to a somewhat more distant future, where plenty of green electricity is available from solar or wind power, then this technology could become important. What potential do you see for Direct Air Capture in the medium and long term?
Creutzig: I see relatively great potential, partly because it is compared to another, very often discussed technology, namely bioenergy and bioenergy with carbon capture and storage, i.e. the binding of CO2 by burning wood mass, for example, compared to this Technology, Direct Air Capture is very little land intensive, it uses much less land resources and is far more scalable technologically, there are better learning curves here. That’s why I see direct air capture, if at all, as a possibility to stabilize the climate in the second half of the century. So one should go in that direction.
Avoid CO2 now
Krauter: The technology is currently being tested on a larger pilot scale, including in Switzerland. What would have to happen now so that we can actually tap this potential, which you have just outlined, in ten or 20 years, when, hopefully, there will be plenty of green electricity available?
Creutzig: We have to think in two directions here. I argued before that climate protection should now primarily focus on conventional measures to really avoid CO2 that is emitted. At the same time, however, we have to think about what should happen after 2040, 2050, which means that we now actually need research initiatives and the opportunity to try out what also works on scale. This means that we must continue to invest in research into sensible and efficient direct air capture.
Think about research investments
Krauter: Does what you have now found have anything to do with the current climate conference in Glasgow? And if so, what would be the essence that you would distill for the negotiators there?
Creutzig: An important point is that, on the one hand, the climate goals up to 2040, 2050 are ambitiously thought – and that would actually work independently of Direct Air Capture – but that at the same time, thinking beyond these goals is also considered, that research investments are also considered, which then just follow Possibly compensate for CO2 emissions in 2050 and that also enable the richer nations, which have also built up a lot of CO2 debts, to then make their contribution.
Statements by our interlocutors reflect their own views. Deutschlandfunk does not adopt statements made by its interlocutors in interviews and discussions as its own.
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