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Concept
Direct air capture
Summary
Direct air capture (DAC) is the use of chemical or physical processes to extract carbon dioxide directly from the ambient air. If the extracted is then sequestered in safe long-term storage (called direct air carbon capture and sequestration (DACCS)), the overall process will achieve carbon dioxide removal and be a "negative emissions technology" (NET). As of 2022, DAC has yet to become profitable because the cost of using DAC to sequester carbon dioxide is several times the carbon price.
The carbon dioxide () is captured directly from the ambient air; this is contrast to carbon capture and storage (CCS) which captures from point sources, such as a cement factory or a bioenergy plant. After the capture, DAC generates a concentrated stream of for sequestration or utilization or production of carbon-neutral fuel and windgas. Carbon dioxide removal is achieved when ambient air makes contact with chemical media, typically an aqueous alkaline solvent or sorbents. These chemical media are subsequently stripped of CO2 through the application of energy (namely heat), resulting in a CO2 stream that can undergo dehydration and compression, while simultaneously regenerating the chemical media for reuse.
When combined with long-term storage of , DAC is known as direct air carbon capture and storage (DACCS or DACS). It would require renewable energies to power since approximately 400kJ of energy is needed per mole of CO2 capture. DACCS can act as a carbon dioxide removal mechanism (or a carbon negative technology), although it has yet to be profitable because the cost per tonne of carbon dioxide is several times the carbon price.
DAC was suggested in 1999 and is still in development. Several commercial plants are planned or in operation in Europe and the US. Large-scale DAC deployment may be accelerated when connected with economical applications or policy incentives.
In contrast to carbon capture and storage (CCS) which captures emissions from a point source such as a factory, DAC reduces the carbon dioxide concentration in the atmosphere as a whole.
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Related concepts (21)
Direct air capture
Direct air capture (DAC) is the use of chemical or physical processes to extract carbon dioxide directly from the ambient air. If the extracted is then sequestered in safe long-term storage (called direct air carbon capture and sequestration (DACCS)), the overall process will achieve carbon dioxide removal and be a "negative emissions technology" (NET). As of 2022, DAC has yet to become profitable because the cost of using DAC to sequester carbon dioxide is several times the carbon price.
Carbon-neutral fuel
Carbon-neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In practice, this usually means fuels that are made using carbon dioxide (CO2) as a feedstock. Proposed carbon-neutral fuels can broadly be grouped into synthetic fuels, which are made by chemically hydrogenating carbon dioxide, and biofuels, which are produced using natural CO2-consuming processes like photosynthesis. The carbon dioxide used to make synthetic fuels may be directly captured from the air, recycled from power plant flue exhaust gas or derived from carbonic acid in seawater.
Carbfix
Carbfix is an Icelandic company that has developed an approach to capturing and storing CO2 in water, and its injection into subsurface basalts. Once in the subsurface, the injected CO2 reacts with the host rock forming stable carbonate minerals, thus providing storage of the captured gas. Approximately 200 tons of CO2 were injected into subsurface basalts in 2012. Research results published in 2016 showed that 95% of the injected CO2 was solidified into calcite within 2 years, using 25 tons of water per tonne of CO2.
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