Thursday, March 24, 2011

Artificial Trees!

Now, this is an interesting idea! Given hat man is entirely hopeless at protecting the environment and compelled by some inner voice to make ash out of any remaining beauty in his path, this concept might actually take off, if only for the selfish need that we have for oxygen.

The idea is this - create artificial trees that would absorb CO2 out of humidity by a technique called humidity swing (more on this later).  They would also be equipped with solar panels to create energy to drive this process. Further, a see-saw below the tree would encourage people to play on it thereby creating more energy to be diverted to the absorption process. Excess energy would be used to light up the tree at night which would then serve as a pretty street light!
Hmmm....thats the first thought that came to my mind.
And the next one, what is this humidity swing process anyway?
and the third, what would the tree do with the CO2 it extracts from the humidity?
Oh, and another thing, the tree would be made out of recycled plastic from old bottles and what not.

To the second thought....A paper by Klaus Lackner and Allen Wright from Columbia University proposes a method of CO2 capture using a humidity swing sorbent.
Two things here,
1. Humidity swing is the process of raising the relative humidity (called RH ;) )  to a large value for a while and then returning it to normal value.
2. A sorbent is basically an absorbent, a material that absorbs another.
So this is how it works...
1. A dry resin absorbs CO2.
This dry resin consists of +ve ions fixed to a polymer matrix and free -ve ions (OH-)
OH- + CO2 -> HCO3-

2. The resin is wet with water.

3. When the CO2 saturated resin reacts with water it releases CO2 at a higher pressure. The resin is then ready to be used again as in step 1.
2HCO3- -> H2O + CO2 + CO3-
This the resin regeneration phase.

4. Drying of the resin
When the water and CO2 are released, the RH of the resin drops to the original value and it is ready for reuse.

Now coming to the question of the CO2 that would be stored and then released....where would it be stored? What happens to the CO2 when it becomes time to regenerate the resin? Will the saturated resin be unsaturated in an enclosure that traps the CO2 when it is released from the resin? If so, wha would they do with it once captured? Release it into space? solidify it and bury it?
And a new question that has popped into my head just now....where's the O2 in this process generated from? I wonder if the news articles were misleading.... Rather an unsatisfactory understanding at this stage...but when I do get more detailed information, I'll be sure to update :)

Links :
The news article in the bangalore mirror -
The paper -

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