The level is thehighest in human history, and is growing each year.
The world must actively remove historical CO2 already in the atmosphere a process often described as negative emissions.
CO2 removal can be done intwo ways.
However, a wartime level of funding from government and business would be needed.
So is direct air capture worth the time and money?
Direct air capture of CO2 will be needed to address climate change.
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Whats DAC all about?
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Plants operating todayuse aliquid solvent or solid sorbent to separate CO2 from other gases.
Swiss companyClimeworksoperates 15 direct air capture machines across Europe, comprising the worlds first commercial DAC system.
The operation is powered by renewable geothermal energy or energy produced by burning waste.
The machines use a fan to draw air into a collector, inside which a selective filter captures CO2.
Once the filter is full, the collector is closed and the CO2 is sequestered underground.
Canadian companyCarbon Engineeringuses giant fans to pull air into a tower-like structure.
The CO2 is then concentrated, purified, and compressed.
The proponents of theClimeworksandCarbon Engineeringtechnology say their projects are set for large-scale investment and deployment in coming years.
Globally, the potential market value of DAC technology could reach US$100bn by 2030, onsome estimates.
Artist impression of a DAC facility to be built in the US state of Texas.
If built, it would be the largest of its kind in the world.
The economic feasibility will be helped by the recent emergence of newcarbon marketswhere negative emissions can be traded.
DAC machines process an enormous volume of air, and as such are veryenergy-intensive.
In fact,researchhas suggested direct air capture machines could use a quarter of global energy in 2100.
Howevernew DAC methodsbeing developed could cut the technologys energy use.
DAC technology is also increasingly gaining the backing of big business.
Microsoft, for example,last year includedthe technology in its carbon negative plan.
Direct air capture is touted as a way to offset emissions from industry and elsewhere.
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Opportunities for Australia
Australia is uniquely positioned to be a world leader in direct air capture.
It boasts large areas of land not suitable for growing crops.
It has ample sunlight, meaning there is great potential to host DAC facilities powered by solar energy.
Australia also has some of the worlds best sites in which to sequester or store carbon in underground reservoirs.
Direct air capture is a relatively new concept in Australia.
Australian companySouthern Green Gas, as well as theCSIRO, are developing solar-powered DAC technologies.
If DAC technology can overcome its hurdles, the benefits will extend beyond tackling climate change.
It would create a new manufacturing sector and potentially re-employ workers displaced by the decline of fossil fuels.
Australia has ample sunlight and plenty of non-arable land where DAC facilities could be built.
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Looking ahead
The urgency of removing CO2 from the atmosphere seems like an enormous challenge.
DAC technology undoubtedly faces stiff headwinds.
