Humanity’s delay in reducing greenhouse gas emissions, which set a new record in 2023, has pushed technologies to remove and store CO2 from the atmosphere to the fore in an attempt to limit global warming, AFP reports.

There are two different groups of techniques that are sometimes confused: carbon capture and storage (CSC) and direct air capture (DAC), also known as carbon removal.

prevent

Should we prevent carbon “pollution” in the atmosphere or clean it up after the damage is done? These are two different roles of CSC and DAC.

• CCS captures carbon emitted by businesses (power plants, cement plants, blast furnaces, etc.) from burning fossil fuels or industrial processes before it is released into the atmosphere.
• DAC extracts the CO2 already in the air using large fans and chemical processes.

Thus, this technique allows for “negative emissions” to be accounted for in the carbon balance of the companies or countries that use it, provided that the captured CO2 is permanently stored, for example in depleted oil and gas reservoirs or saline aquifers.

However, the CO2 molecules present in the air are much more rarefied – 420 parts per million (ppm), or about 0.04% – than when they come out of a factory chimney, making the technique energy-intensive and expensive.

In both cases, the captured CO2 can be permanently stored or reused to produce building materials or aviation fuel.

But reuse means an inevitable return to the air and can no longer be considered disposal.

Current situation

The fossil fuel industry has been using CSCs since the 1970s… but not to keep carbon out of the atmosphere.

Originally, this process was used to inject CO2 into old fields to extract hard-to-find oil. But the climate crisis and government subsidies have renewed the fossil fuel industry’s interest in using it to reduce emissions, even if it remains unprofitable.

According to the International Energy Agency (IEA), by the end of 2023, 40 commercial companies worldwide will be using this technology, sequestering a total of 45 million tons (Mt) of CO2. This represents approximately 0.1% of annual global emissions.

Decarbonation (DAC) is a recently developed technique. It is used by fewer than thirty plants worldwide, capable of removing about 10,000 tons of CO2 per year, equivalent to 10 seconds of global emissions.

The need for acceleration

According to the IEA, to meet the net-zero emissions goal by 2050, CSC will need to prevent 1.3 billion tons of CO2 emissions per year by 2030, 30 times more than today.

As for the DAC, at that time it will have to extract 60 million tons of CO2 per year, thousands of times more than today.

While that goal may seem out of reach, recent developments offer some hope: at least 130 projects are under development, and the first facility capable of harvesting up to one million tons per year is due to become operational in the United States in 2025, according to the IEA.

“It’s a huge challenge, but it’s not unprecedented,” Gregory Nemeth, a professor at the University of Wisconsin, told AFP, recalling the impressive growth of solar energy in just a few decades.

There remains the question of storage: preparation of a lens can last up to 10 years, which is a serious obstacle.