Down to Earth: Carbon capture

25 July 2017

Interview with

Stuart Higgins

In this week’s Down to Earth, where we take a look at tech intended for space which has since found a new home down here on Earth, physicist Stuart Higgins looks at a technology to soak up CO2…

Stuart - Every day we each breath out about a kilogram of carbon dioxide, depending on how active we’ve been. Back down on Earth, the carbon dioxide we produce forms part of the carbon cycle. It’s used by plants in photosynthesis to grow into crops that we eat and then so on...

But when you’re orbiting the Earth in a space station one or two houseplants aren’t going to be enough to keep up with the CO2 you’re producing. Without a means of removing carbon dioxide the concentration in the air will quickly rise to dangerous levels. So one of the key technologies for space exploration is carbon dioxide absorbers. These are chemical sponges that mop up the excess carbon dioxide in the air allowing astronauts to breath freely.

The European Space Agency ESA has been working on a new life support system called the Advanced Closed Loop System for the International Space Station which will help scrub the air of carbon dioxide as well as generating oxygen and water. It’s designed to remove 3 kilograms of carbon dioxide per day, the equivalent of roughly three astronauts, will work alongside existing systems on the space station. It works by passing the carbon dioxide-containing air across a bed of absorbant beads. The beads are made up of a resin coated in a solid amine based chemical.

Amine is the name given to a chemical compound with a nitrogen atom that has a spare pair of electrons. And by spare, I mean that these particular electrons aren’t directly forming chemical bonds with other atoms in the compound. These spare electrons make the amine group reactive, they’ll bind with the slightly acidic carbon dioxide flowing over them.

Eventually, the beads will absorb as much carbon dioxide as they can. At this point, the absorber can be shut off from the rest of the spacecraft and steam passed over the beads. This causes the release of carbon dioxide which can then either be released into space or used in other experiments on board the space station.

The same technology is now being used back on Earth to capture carbon dioxide from the atmosphere. Rather than using it to keep astronauts alive, a Dutch company has developed the same ESA technology to extract carbon dioxide from the atmosphere. They aim to use it to improve the atmosphere in closed environments such as airplanes and crowded buildings. And as a way of producing a continuous carbon for example for farmers who might want to raise the carbon dioxide levels in their greenhouses to help plants grow.

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