High hopes for carbon capture, underground storage

Capturing carbon dioxide (CO2) from the atmosphere to store underground "sounds too good to be true", a climate expert told AFP, yet the technology to increase its capacity tenfold is already being tested.

The Intergovernmental Panel on Climate Change (IPCC) recognises carbon capture and storage among the solutions for eliminating CO2, without giving it a central place in its models.

"The small DACCS (direct air capture with carbon storage) ecosystem gets more diverse... but we're not exactly sure where this will lead to" in the fight against climate change, said Oliver Geden, an IPCC member and specialist on carbon dioxide removal.

Even if the capacity to capture CO2 reaches two billion tonnes in 2050, compared with just 10,000 today, as suggested by optimistic projections in a report by the University of Oxford, experts are categorical: we must first massively reduce emissions of greenhouse gases like CO2 into the atmosphere and consider carbon capture and storage only for emissions that can't be eliminated.

Companies like Microsoft, Amazon, Airbus and even Lego are already paying upwards of $1,000 per tonne of CO2 captured and stored -- in the form of carbon credits -- to offset their emissions.

How it works

Molecules of CO2 in the air pass through large fans and are absorbed by a liquid filter or deposited on a solid filter.

Once the filters are full, the fans close and the filters are heated to high temperatures upwards of 120 degrees Celsius for solid filters and 900 degrees Celsius for liquid filters in order to release pure CO2.

This heating requires substantial use of energy and the development of these technologies on a large scale depends on the availability of electricity...