Long seen as fringe or a ploy by industry to avoid reducing emissions, carbon dioxide removal (EDC) measures are now a necessary tool, according to the Intergovernmental Panel on Climate Change (IPCC).

"This is the first IPCC report to make it clear that removing CO2 is necessary to meet our climate goals," said Steve Smith, head of the Oxford Net Zero initiative at the University of Oxford. .

The Paris agreement calls for limiting warming to below 2°C, or even 1.5°C, compared to the second half of the 19th century.

According to the most ambitious emission reduction scenarios, several billion tonnes of CO2 will have to be removed from the atmosphere each year by 2050 – compared to current emissions of around 40 billion tonnes per year.

This could be used in sectors where emissions will be difficult to reduce, such as air and maritime transport, or cement.

Or to cool the atmosphere if the limits of the Paris agreement are exceeded.

A detail of the CO2 capture pilot plant installed in the Amager Bakke waste incinerator in Copenhagen on June 24, 2021 Ida Guldbaek Arentsen Ritzau Scanpix/AFP/Archives

In a study published in mid-March, the Norwegian energy research firm Rystad Energy estimated that the market for CO2 capture and storage equipment would quadruple between 2022 and 2025, to reach a cumulative total of more than 50 billion dollars in 2025.

Grow, burn, bury

There are different methods to achieve these "negative emissions".

All the IPCC models reserve a significant part for the technique of bioenergy with capture and storage of carbon dioxide, which consists in growing trees which absorb CO2 during their growth, then burning them in order to produce energy ( biomass) and to bury the CO2 resulting from this combustion, in abandoned mines for example.

By 2050, this would eliminate just under 3 billion tonnes of CO2.

For a result of the same order of magnitude, another solution is to restore forests and plant trees to absorb and store CO2, through photosynthesis.

In the Peruvian Amazon, Vittel (Nestle Waters) has invested 409,000 euros in the planting of 130,000 trees to compensate for the 115,000 tonnes of CO2 produced in their mineral water factories in France and Belgium, February 14, 2010. - AFP /Archives

But what works on paper does not yet materialize.

One of the few commercial-scale bioenergy projects in the world, in the UK, has been removed from the S&P Clean Energy stock index after failing sustainability criteria.

The land area needed to significantly reduce CO2 levels by planting trees – up to twice the size of India – could strain crops for food or biodiversity.

Clearing systems

The most recent technology, the direct capture of CO2 in the air and its storage, via chemical processes, is also attracting interest.

The Swiss company Climeworks, one of the leaders in the sector, announced on Tuesday that it had raised 650 million dollars, the day after the publication of the IPCC report.

The Climeworks factory in Hellisheidi near Reykjavik on October 11, 2021 Halldor KOLBEINS AFP/Archives

But the potential for large-scale projects remains to be proven: Climeworks' facilities in Iceland - the largest in the world - eliminate in one year what humanity emits in three or four seconds.

Other EDC techniques are in various stages of experimentation and development: improving the ability of soils to sequester carbon, converting biomass into a charcoal-like substance called biochar, restoring peatlands and coastal wetlands, or "augmented weathering", i.e. the crushing of rocks rich in minerals that absorb CO2 to spread them on land or at sea.

The oceans already absorb more than 30% of humanity's carbon emissions, and scientists are experimenting with ways to increase this capacity, for example by artificially boosting marine alkalinity or by "fertilizing" the oceans, c ie by increasing the density of phytoplankton which produces and sequesters organic carbon by photosynthesis.

© 2022 AFP