Direct air capture
Carbon dioxide is pulled out of ambient air using absorptive substances that selectively bind to CO2 . A company called Carbon Engineering uses fans to pull air across an absorbant membrane. There, CO2 is converted into a carbonate solution, which can be processed to trap the carbon.
Fans pull air
converted into a carbonate solution and then pure carbon is separated.
Pulls CO2 from all sources, not just power plants with smokestack-collection systems.
Low land use and can be scaled up to fit local demand.
Technology is still being developed.
Not available on a commercial scale yet.
Bioenergy combined with carbon capture and storage (BECCS)
Trees or other forms of biomass are burned in power plants and replanted. Power plants capture, compress and send carbon dioxide to sequestration sites, where it is buried or used for enhanced oil recovery.
to carbon sequestration site
Both technologies already exist
Carbon sequestration technology has not been widely adopted yet
Requires a very large amount of land to have a significant effect on CO2 levels.
Trees are planted in an area where a forest does not exist. Trees and vegetation consume carbon dioxide as they grow.
Totally passive, relatively inexpensive and easy.
The amount of land required to have an affect on CO2 levels would be extremely large and would compete with other uses.
Slightly acidic rain falls on silicate rocks and they slowly break down to a carbonate solution. The carbon in the rain eventually winds up embedded in limestone rocks.
Could substantially remove CO2 from the air
Natural process could be scaled up for greater CO2 removal
To do this on an industrial scale would involve extracting and distributing rock.
The crushed rock particles could cause major health problems if inhaled.
Large-scale costs would be high.
A fledgling technology, carbon sequestration injects compressed CO2 deep into the earth inside stable geologic formations. It can also be used to help extract oil and natural gas.
Carbon sequestration through enhanced oil recovery
Liquid CO2 from a power plant is transported by pipeline to drill sites where it is injected into depleted oil and gas reservoirs. The carbon dioxide aids in the extraction of oil, ensuring maximum production. After the reservoir has been exhausted, the well is capped and the carbon dioxide is trapped.
CO2 injected into
Carbon sequestration into geologic formations
Liquid CO2 is transported by pipeline to a storage site where it is injected into rock formations that hold, or once held, fluids. Injecting CO2 deeper than 800 meters will allow the natural pressure of the Earth to keep it in a liquid state, which makes it less likely to migrate out of the formation. In deep saline formations, salt water, called brine, is stored in the rocks' pores. The CO2 will eventually dissolve and mineralize, becoming part of the rock formation.
CO2 injected into
deep saline formations