FILTERS AGAINST CLIMATE CHANGE

TEXT LARS-THORBEN NIGGEHOFF
ILLUSTRATION SEÑOR SALME

—— Combating climate change without “negative emissions” won’t be possible. Emitted pollutants must be captured. One method is known as Direct Air Capture (DAC), and the recovered carbon dioxide can be useful in other areas over the long term.

THE METHODS

DAC processes require huge fan blowers. These pull in air containing carbon dioxide, filter it and then expel it. There are two ways to capture the gas: amine scrubbing uses a solvent derived from ammonia that separates carbon dioxide out of the air. With carbon-dioxide absorption, a substance such as caustic soda reacts with the carbon dioxide to form a compound, which is then split to obtain pure the carbon dioxide.

THE PIONEERS

Companies around the world are working to make DAC viable on a large scale. Big pilot projects can be found in Switzerland, Iceland and in the United States, for example. Various manufacturers are also competing to offer the lowest price per extracted ton: this currently ranges from 90 to 250 euros, depending on the company.

CO² Absorption

CO2 is absorbed and converted into sodium carbonate.
PHASE 1 CO2 reacts with sodium hydroxide to form sodium carbonate.
Illustration of the release of pure CO2 and its collection.
PHASE 2 The sodium carbonate is heated to release pure CO2. The CO2 is then removed from the filter and collected.
Illustration of the storage of CO2 in a cavity.
UNDERGROUND STORAGE After the filtering process, the carbon dioxide can be stored. This usually occurs in underground cavities known as saline aquifers, the pores of which are filled with salt water. Deep, non-degradable coal seams are also suitable for this storage.

CO² APPLICATIONS

Illustration of a turquoise component on a white background

CONSTRUCTION MATERIALS

Carbon dioxide can be ­mineralized into calcium carbonate, which can be used to manufacture concrete or asphalt. Furthermore, carbon dioxide can also replace water for mixing concrete.

Illustration of a yellow-blue nozzle head on a white background.

LIQUID FUELS

In simple terms, these fuels are made up of three parts: hydrogen, energy and carbon molecules such as carbon dioxide. For the fuels to be beneficial for the climate, the hydrogen used must be green hydrogen.

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ALGAE

Carbon dioxide can be used to fertilize algae. In turn, the algae can be used for foodstuffs, biofuel, plastics or carbon fiber. Algae also ­remove carbon dioxide from the ­atmosphere.

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