On Wednesday this week, the concentration of carbon dioxide in the atmosphere was measured at at 415 parts per million (ppm). The level is the highest in human history , and is growing each year.
Amid all the focus on emissions reduction, the Intergovernmental Panel on Climate Change (IPCC) says it will not be enough to avoid dangerous levels of global warming. The world must actively remove historical CO₂ already in the atmosphere – a process often described as “negative emissions”.
CO₂ removal can be done in two ways . The first is by enhancing carbon storage in natural ecosystems, such as planting more forests or storing more carbon in soil. The second is by using direct air capture (DAC) technology that strips CO₂ from the ambient air, then either stores it underground or turns it into products.
US research published last week suggested global warming could be slowed with an emergency deployment of a fleet of “CO₂ scrubbers” using DAC technology. 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. What’s DAC all about?
Direct air capture refers to any mechanical system capturing CO₂ from the atmosphere. Plants operating today use a liquid solvent or solid sorbent to separate CO₂ from other gases.
Swiss company Climeworks operates 15 direct air capture machines across Europe, comprising the world’s 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.
Read more: Net-zero, carbon-neutral, carbon-negative … confused by all the carbon jargon? Then read this
Canadian company Carbon Engineering uses giant fans to pull air into a tower-like structure. The air passes over a potassium hydroxide solution which chemically binds to the CO₂ molecules, and removes them from the air. The CO₂ is then concentrated, purified and compressed.
Captured CO₂ can be injected into the ground to extract oil , in some cases helping to counteract the emissions produced by burning the oil.
The proponents of the Climeworks and Carbon Engineering technology 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, on some 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. Big challenges ahead
Direct air capture faces many hurdles and challenges before it can make a real dent in climate change.
DAC technology is currently expensive, relative to many alternative ways of capturing CO₂, but is expected to become cheaper as the technology scales up. The economic feasibility will be helped by the recent emergence of new carbon markets where negative […]
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