Interview with Franz May, BGR: “A broad bundle of measures” – knowledge

Capture carbon dioxide and press it underground – this is what the abbreviation CCS stands for, “Carbon Capture and Storage”. Such approaches are a prerequisite for most ambitious climate protection scenarios. “Orca” recently went into operation in Iceland, where 4,000 tons of CO₂ are to be filtered out of the air and brought into the ground every year. In Norway, CO₂ from industrial plants has been stored for a long time. In Germany, however, the technology is in a difficult position. At the moment, no storage applications can be made nationwide; several federal states have completely ruled out CCS. And how much space is there in the underground anyway? Franz May is an expert in CO₂ storage at the Federal Institute for Geosciences and Natural Resources (BGR).

SZ: How much greenhouse gases could we store underground in Germany?

Franz May: From a geological point of view, Germany has great storage possibilities in empty natural gas reservoirs and saline aquifers, i.e. in salt water layers at great depths. Natural gas reservoirs would be options because they have held back natural gas for millions of years, i.e. in principle they seal them off very well. We are talking about a volume of 2.7 billion tons of carbon dioxide. The volume of deep saline aquifers can be estimated at 6.3 to 12 billion tons, more precise data are lacking. Currently, however, no CO₂ can be stored underground in Germany because the deadline for applications for storage under the Carbon Dioxide Storage Act expired at the end of 2016.

Do the research results so far justify the skeptical attitude of politics?

The separation, transport and storage of CO₂ are technically possible; geologically speaking, there are layers that are probably suitable and worthy of investigation. Research is still being carried out into cheaper, lower-energy separation processes and into autonomous monitoring techniques. But these are more development than research aspects. In Germany, demonstration projects would make more sense in order to specifically examine the feasibility, for example with regard to the question of how individual rock formations behave when they are stored. From a geological point of view, however, there is nothing against further developing CO₂ storage in Germany.

Franz May, geoscientist at the Federal Institute for Geosciences and Natural Resources.

(Photo: BGR)

Do you look abroad with a certain envy?

There is no need to jealously look abroad because the conditions are different everywhere, not only the geological, but also the socio-economic. CO₂ storage is just one of many options when it comes to climate protection. However, it is particularly worth taking a closer look at Norway, where in the marine area CO₂ is also stored in former natural gas reservoirs under the sea. The Norwegians are very far. There were setbacks there too, but these could be remedied technically.

Can you also learn something from this about the possible risks of CO₂ storage?

From a climate protection perspective, the CO₂ should be kept away from the atmosphere for at least a few thousand years if it is stored. We have no experience from storage projects for these periods. Norway has 25 years of experience and the project is running smoothly. But there are natural CO₂ storage sites, including in Germany. On the basis of these, we can at least estimate which deposits were tight and where CO₂ leaked. Careful exploration, selection and monitoring are therefore basic requirements for any project. In addition, laboratory experiments and computer simulations help with long-term prognoses.

What do these natural camps tell us?

Some surface layers have held back CO₂ for more than ten million years – for example the Zechstein, which can also be found in Germany. Another aspect: where there are natural CO₂ emissions, we can study its environmental impact, such as the rate of gas escaping. Above some CO₂ storage sites at great depths there are layers of rock with a somewhat higher permeability, which, however, can also serve as intermediate storage. Nature offers a multi-barrier concept.

Federal Research Minister Anja Karliczek particularly emphasizes the role of natural sinks such as forests, moors and oceans. Is that the right focus?

There are studies on the question of which technologies can be used to achieve the 1.5 degree target: These are all scenarios that contain a broad mix of measures. The one does not exclude the other. This includes natural sinks, but also technical measures. However, if you look at CO₂ storage worldwide, it becomes clear that emissions rise much faster than the capture options. That is why we need a wide range of measures. First and foremost, however, it must be about avoiding emissions.

Isn’t avoidance enough?

Above all, we need CCS as a solution for process-related emissions in industry. Therefore, CCS is at least a bridging technology until we have managed to switch to renewable energies and renewable raw materials or industrial processes can be redesigned. There is also the discussion about CO₂-neutral hydrogen – one technique here is to extract hydrogen from natural gas and store the resulting CO₂.

A plan that natural gas-rich Norway is pursuing. Are storage sites in the sea also considered off the German coast?

In the German North Sea region there is still no detailed study of the suitability of geological formations for CO₂ storage. The formations worth investigating would have to be characterized much more precisely. In principle, however, it makes no difference for storage whether there is only rock above the storage or, as in the North Sea, an additional 50 meters of water. But it makes differences in exploration, monitoring and drilling.

What about the earthquake risk? That is often used as a counter-argument.

When it comes to CO₂ storage, I am not aware of any project that failed due to an earthquake. Noticeable quakes, including those that caused slight damage to buildings, are known from other individual geotechnical projects. They occurred where critical tensions existed in the subsurface before gases and liquids were injected or withdrawn. That was then symbolically the drop that made the barrel overflow.

The regions that are suitable for CO₂ storage, such as the North German Basin, the South German Basin and the Upper Rhine Rift, are often also of interest for deep geothermal energy. Is there a threat of land conflicts?

At the moment I don’t see any conflicts of use as there are only a few projects for both technologies. In addition, the underground is a three-dimensional space in which we can use different floors. There are also first international ideas to combine geothermal energy and CCS, for example to relieve pressure in aquifers. A side by side is therefore conceivable.

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