The US government said Friday it will spend up to $1.2 billion for two pioneering facilities to vacuum carbon out of the air, a technology to combat global warming that is not universally praised by experts. 

The two projects -- in Texas and Louisiana -- each aim to eliminate one million tons of carbon dioxide per year, equivalent in total to the annual emissions of 445,000 gas-powered cars.

Carbon dioxide (CO2) emissions fuel climate change and extreme weather.

"Today's announcement will be the world's largest investment in engineered carbon removal in history," the Energy Department said in a statement.

"Cutting back on our carbon emissions alone won't reverse the growing impacts of climate change," Energy Secretary Jennifer Granholm said in the statement. "We also need to remove the CO2 that we've already put in the atmosphere."

Each of the projects will remove 250 times more CO2 from the air than the largest carbon capture site currently in operation, the Energy Department said.

Swiss company Climeworks, a sector leader, currently operates a plant in Iceland with an annual capacity to capture 4,000 tons of CO2 from the air.

Climeworks will take part in the Louisiana project, which will inject captured CO2 for storage deep underground.

The scale of existing carbon capture sites in the world -- 27 currently commissioned in total -- is small, according to the International Energy Agency (IEA).

More than 130 projects are currently under development, the IEA says.

The new investments by President Joe Biden's administration are part of a major infrastructure bill passed in 2021. The Energy Department previously announced plans to invest in four projects to the tune of $3.5 billion.

The UN's International Panel on Climate Change considers capturing carbon dioxide directly from the atmosphere one of the methods necessary to combat global warming.

But some experts worry that use of the technology will be a pretext for continuing to emit greenhouse gases, rather than switching more quickly to clean energies.

These Direct Air Capture (DAC) techniques -- also known as Carbon Dioxide Removal (CDR) -- focus on the CO2 already emitted into the atmosphere. They differ from carbon capture and storage (CCS) systems at source, such as factory chimneys, which prevent additional emissions from reaching the atmosphere.

In May, the Biden administration announced a plan to reduce CO2 emissions from gas-fired and coal-fired power plants, focusing in particular on this second technique.  

la/tjj/cl