The world will have to resort to capturing and storing CO2 from the air and oceans regardless of the rate of decline in greenhouse gas emissions.

Carbon Dioxide Removal (EDC) measurements are now a necessary tool, according to the Intergovernmental Panel on Climate Change (IPCC).

"This is the first IPCC report to state clearly that removing CO2 is necessary to achieve our climate goals," said Steve Smith, of the Oxford Net Zero initiative at the University of Oxford.

To limit global warming to between 1.5 and 2°C as provided for in the Paris Agreement, several billion tonnes of CO2 will have to be extracted from the atmosphere each year by 2050.

Bioenergy, a solution for the future?

This solution could be used in sectors where it is difficult to reduce emissions (air and maritime transport, cement) or to cool the atmosphere if the limits are exceeded.

In a study published in mid-March, Norwegian energy research firm Rystad Energy estimated that the CO2 capture and storage market would quadruple between 2022 and 2025.

Different techniques exist to achieve these “negative emissions”.

A significant part is given to bioenergy, which consists of growing trees that absorb CO2 during their growth, then burning them in order to produce energy (biomass) and burying the CO2 resulting from this combustion.

Bioenergy would eliminate nearly 3 billion tonnes of CO2 by 2050.

Still insufficient results

But what works on paper does not yet materialize.

A British commercial-scale bioenergy project has been removed from the S&P Clean Energy stock index after failing sustainability criteria.

The land area required (up to twice the size of India) could weigh on crops for food or biodiversity.

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.

But the potential remains to be proven: the Climeworks facilities in Iceland eliminate in one year what humanity emits in three or four seconds.

The oceans at the heart of research

Other EDC techniques are in various stages of experimentation: improving the ability of soils to sequester carbon, converting biomass into a charcoal-like substance called biochar, restoring peatlands and wetlands coastal…

The oceans already absorb more than 30% of humanity's carbon emissions.

Scientists are experimenting with ways to increase this capacity, such as by artificially boosting marine alkalinity or by "fertilizing" the oceans, i.e. increasing the density of phytoplankton which produce and sequester organic carbon through photosynthesis. .

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