As no one has picked me up in the 'crap plastic trees' post I made earlier I'll take that as 'the stupid old duffer doesn't know what he's on about', so let's have a quick chemistry lesson.
The reaction the 'scientists' are on about is using lime water to react with CO2 in the atmosphere to produce limestone.
Ca(OH)2 + CO2 ---> CaCO3 + H2O
The atomic weights of the above are 74, 44 for the reactants. Let's call it 2:1 for simplicity. This means that for every tonne of lime water you can absorb 2 tonnes of CO2. Sounds good in paper.....so far.
But the plastic leaves need to be kept wet either with water or preferably with more lime water which will take a small amount of power to pump it up the tree. Pump too much and you could end up with excess lime water dripping on the ground which could affect the environment not to mention the hazard of having containers of lime water hanging around where anyone or anything could get to it. There's also the energy involved to make the metal frame of the fake trees and the energy and oil (oh dear) to make the plastic.
Not looking so good now is it?
However it gets much worse.
To make lime water you need 2 things (there's a clue in its name). So how do you make the lime water.... It's from lime
CaO + H2O ---> Ca(OH)2
This reaction is highly exothermic i.e gives off heat in fact it can make the water boil which should give a clue as to what happens earlier.
To make the lime you need to roast limestone at around 900°C
CaCO3 + lots of heat ---> CaO + CO2
The carbon dioxide is given off to the atmosphere.
The atomic weights are 100 for limestone and 44 for the CO2 which is again roughly 2:1 so for each tonne of limestone you roast you get 2 tonnes of CO2 given off.
In this whole process you have given off 2 tonnes of CO2 to absorb 2 tonnes of CO2 plus all the energy and oil to produce the explosives to break up the limestone in the quarry, plus all the oil used by the machinery to collect and move the limestone, plus the huge amount of energy used to roast the limestone, plus the energy used to produce the metal frame of the trees and the oil used to make the plastic etc etc etc.
tldr: Basically you put more CO2 into the atmosphere than you take out.
Any 'scientist' that thinks this is a good idea should have their degree taken of them.
I've not looked into it but I hope these machines that are being developed to pump CO2 from the atmosphere don't use the same chemistry.