(IN THE HENGILL VOLCANIC MASSIVE) Below the steep slopes of a volcanic massif in Iceland, a new kind of plant sucks in the ambient air to capture the CO2, the main cause of global warming, before imprisoning it in the underground basalt.
A steel monster raised by concrete slabs and connected to a maze of pipes, Orca – “orka” meaning “energy” in Icelandic – is the largest plant in the world designed to capture carbon dioxide directly from the air and then transform it into rock.
A pilot project that differs from the traditional CO capture2 at the exit of the chimneys of polluting industries.
Launched last September by Swiss start-up Climeworks, this 1,700 square meter facility is the result of an alliance with CarbFix, an Icelandic company pioneering underground carbon storage, and ON Power, operator of the neighboring geothermal power plant. by Hellisheidi.
Eight maritime transport containers stacked in pairs form a structure about ten meters high. The air is sucked in from the front with a fan and expelled, purified, at the back.
“There is a very selective filter material inside our collection containers which catches the CO molecules.2 », Explains Lukas Kaufmann, project manager at Climeworks.
Injected into the rock
“As soon as the filter is full, we close it and then heat it up to around 100 ° C”, adds the Swiss engineer.
The operation releases the pure gas. First freed of its ultimate impurities, the carbon dioxide is then routed via an underground pipeline more than three kilometers long to injectors sheltered under small gray domes.
Dissolved in water, the gas is finally injected at high pressure into the basalt rock, between 800 and 2000 meters deep.
The aqueous mixture loaded with CO2 penetrates into the rock, porous like a sponge, and solidifies thanks to a chemical reaction of the gas with the calcium, the magnesium and the iron contained in the basalt. In the form of white calcareous crystals, carbon dioxide becomes embedded in the small cavities of the brown rock.
A technique that accelerates in less than two years a natural process called mineralization, which normally takes hundreds of thousands of years.
According to Thomas Ratouis, the French chief engineer of CarbFix, it is the most stable and secure form of carbon storage today.
“What can cause CO2 would be released into the atmosphere again, it would be for the rocks to be heated to a high temperature ”, for example in the event of a volcanic eruption, explains Didier Dalmazzone, professor of chemical engineering at ENSTA Paris.
Orca plant, costing $ 10-15 million, can suck up to 4,000 tonnes of CO2 per year. Derisory whereas current models suggest that several billion should be eliminated each year by 2050.
“We are very lucid about this, but it is very important to learn to walk before knowing how to run”, pleads Julie Gosalvez, marketing manager at Climeworks.
The capture and storage of carbon dioxide in the earth’s subsoil are among the methods encouraged by the International Panel of Climate Experts (IPCC) to contain by 2100 warming to 1.5 ° C compared to the pre-industrial era.
Expensive
As opposed to the most advanced process known as CCS (“carbon capture and storage”) which captures CO2 before it enters the atmosphere from a highly concentrated pollution source on an industrial site, the DAC (“direct air capture”) process attacks the emissions already present in the ambient air.
Many diffuse sources of CO2 (planes, cars, ships, etc.) cannot also be used for upstream collection.
However, experts say the technology is still in its infancy and faces the challenge of low CO concentration.2 in the air.
If the latter broke an alarming new record in 2020, it represents only a tiny part of the air (0.041%).
Orca must therefore treat two million cubic meters of air on average to capture a single tonne of CO.2, a very energy-intensive and expensive process.
If Climeworks refuses to reveal figures, the cost of capturing a tonne of CO2 in the air would cost between 80 and 200 euros according to an estimate by the European Commission in 2019.
For Didier Dalmazonne, one way would be to be content with capturing only two-thirds of the CO2 contained in the sampled air. “It can be less expensive and still do the trick since the goal is to remove CO2 and not all the CO2 “.
If Iceland, where more than 70% of primary energy comes from geothermal energy and which has abundant water resources, seems the ideal playground, the method cannot be copied everywhere.
Carbfix is therefore planning a pilot injection next summer with seawater, to adapt its technique, which currently requires 20 to 25 tonnes of desalinated water per tonne of CO.2.
A port terminal is also due to open soon in Straumsvík Bay at the gates of the Icelandic capital.
Called Coda, it will host the carbon captured on industrial sites in Northern Europe and then be imprisoned in Iceland.
A first vessel in operation should make it possible to treat 300,000 tonnes of CO2 per year in 2025, with a target ten times higher in 2030. According to Carbfix, only 4 to 7% of CO2 would be released into the atmosphere during transport.