If it is economic to capture CO2 from the atmosphere then there are a few advantages.
The challenge is that CO2 is 400 ppm, i.e. only one molecule to 2,500 air molecules. |
Artificial trees. National Geographic |
Oxy-burning biomassThe most obvious way to capture CO2 from the atmosphere is to:
It would take many generations to repair the damage done by this one. It is also referred to as "Bio-energy with carbon capture and storage", or BECCS |
Compressing CO2 will take 7-10% of the energy generated by the power station. Source Firing with pure oxygen would result in too high a flame temperature, so the mixture is diluted by mixing with recycled flue gas, Sounds simple, but as usual, there are technical details . Cost is estimated to be AU$75-150 /Tonne of CO2. Source Source2 That is AU$225-450 /T of coal. |
EthanolWhen ethanol is made by fermentation of sugar, 50% of the sugar becomes ethanol, and 50% becomes CO2. If this is buried, then it is removed from the atmosphere. Bio-charUse pyrolysis to convert biomass to biochar and bury it. See page on biochar |
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Chemical absorptionThere are processes using CO2 absorbers:
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One idea is to react the absorbent in a solar updraft tower. The challenge is to find a substance to absorb the CO2, then to release it again with a minium of energy. For example: NaOH binds the CO2 with ten times the energy needed, and this is how much energy is needed to release the CO2 and recycle the absorbent. Amine estimated cost: US$15-50/T CO2 (US$45-150/T of coal) This depends on how long the amine surfaces last. |
Lithium carbonate and oxideLithium oxide dissolved in molten lithium carbonate, will combine with carbon dioxide in the air, forming lithium carbonate. A voltage across the molten carbonate, produces lithium oxide, (which is recycled) oxygen, carbon. The carbon can be produced as a variety of different carbon nanofibres. This depends on the conditions of the electrolysis. |
Li2O + CO2 → Li2CO3 Li2CO3 → Li2O + C + O2 Researcher: Stuart Licht, professor of chemistry at George Washington University. The researchers claim one million square KM would be enough to repair our carbon dioxide levels. MIT Technology review August 19, 2015 |
Absorption by ion exchange fibresWind can drive air into a funnel and over fibres to absorb the CO2. The energy cost of collection depends on the amount of CO2 captured, rather than with the volume of air processed. It is most economical if only half the CO2 is collected. A process being developed by Klaus Lackner of Columbia University NY traps CO2 on ion exchange membrane and then releases it with water or moist air at 45oC.. The ion exchange resin similar to Dow Chemicals Marathon A , absorbs CO2 with much less binding energy than NaOH. A collection unit with one square meter face area can keep up with one person’s CO2 emissions. A shipping container sized collector should be able to collect one Tonne of CO2 per day, As much as a hectare of crops. |
NaOH + CO2 → Na2CO3 A rough estimate cost would be at first $200/T CO2, but with large scale manufacture, theat may drop to US$30/T of CO2, or US$600-90/T of coal burned. It would take about 25% of a power stations output to collect the CO2.
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Nano tubesNano tubes made mainly of carbon, can absorb CO2. It is released again simply by heating. More |
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