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CDR has two inherent activities - removing carbon dioxide from the atmosphere, and arranging that it is not able to return to the atmosphere; sequestering it. Although many CDR approaches involve some close-coupling of these two activities, there is a degree of independence between them that can give rise to a bewildering variety of separate approaches. Although common use of the words remove and capture gives them similar meaning, in the context of climate change mitigation, they are quite distinct - carbon capture means collecting some or all of the CO2 in an emission source such as a fossil fuel power plant, not removing it from the regular mixed atmosphere. Carbon capture is often referred to as CCS (carbon capture and storage) or CCUS (carbon capture, utilization, and storage). OpenAir is not generally focused on development of CCS, however the CDR approach BECCS incorporates CCS technologies.
Removing CO2 can happen by photosynthesis; making biomass. (RESUME EDITING HERE) It can happen by adsorption on any number of different membranes, liquids, polymers, or other media. It can happen by dissolving CO2 in water such as rain or the ocean surface. It can also happen by physical process of cryogenic separation of air.
Sequestering of carbon can be achieved by biomass storage in forest and other ecosystems living mass or by storing dead biomass where it cannot decompose. It can be sequestered by converting biomass to carbon or by chemically reducing carbon dioxide to elemental carbon or other chemicals. The ocean is a great reservoir of dissolved inorganic carbon, perhaps with additional storage capacity - but because the balance of ocean chemistry is critical to life on Earth, employing significant additional ocean storage is not contemplated. Instead, accelerating the conversion of dissolved carbon to mineral form to create additional ocean storage capacity is an important approach to sequestration. |