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Re: CO2 and slightly off topic


Greg Schraiber asked:

>>I need help from all the chemist and experienced CO2 gurus out there. I am
looking for a way to increase the ambient concentration of CO2 over 
my entire backyard garden (600 sq. ft).<<

I can only foresee 3 major problems. First, without sealing the 
garden off from the surrounding air, i.e. installing some sort of 
greenhouse cover, diffusion of the CO2 into the surrounding air will 
occur at a pace that will make it extremely unlikely that you will 
ever achieve a CO2 concentration sufficiently elevated to have any 
effect on garden plants. You would need to keep pumping copious 
quantities of CO2 into the area to counteract the continual diffusion 
into the atmosphere as a whole. Ultimately the only way to achieve a 
steady state CO2 concentration at an elevated level would be to raise 
the total atmospheric CO2 level across the whole world to your 
desired level. I would think that's unachievable, thank goodness (see 
my next point), but it does highlight the point that it will take 
incredible levels of CO2 pumped constantly into the garden area to 
achieve the outcome you desire on a local level.

Secondly, and more importantly, there could be significant problems 
for you and anyone else working in the garden if you elevate CO2 
levels in the air. The whole process of respiration - oxygen passing 
into the bloodstream through the lungs and CO2 exhalation - depends 
on the normal partial pressures of the various gasses in the 
atmosphere. If you elevate CO2 levels significantly, you can impair 
that process and this can have serious health implications for anyone 
breathing the modified air mixture. In workplaces that use CO2, there 
are strict safety limits on CO2 concentrations in the air in order to 
protect the people working in that environment. You would need to 
monitor the CO2 levels constantly to ensure the safety of yourself 
and anyone else in the garden. That monitoring will require equipment 
that can be quite expensive. CO2 is colourless and odourless and 
there is no other way you can tell that the concentration you are 
breathing is too high until you or someone else starts to feel very 
faint and/or pass out. At that point there is a serious risk of death.

Thirdly, and following on from the second point, without a cover to 
enclose the air space you wish to modify, elevation of CO2 levels 
over your garden will not end at your garden border - it will spread 
to your house, your neighbours, etc etc etc, though the CO2 levels 
would decrease with distance due to diffusion. If things went wrong, 
you could end up gassing the whole neighbourhood, hardly a way to 
endear yourself to your family and others. I would regard this as an 
extremely unlikely possibility given my first point but if you try to 
achieve your stated outcome you will need to consider this issue 
quite seriously.

Your only chance of doing anything is going to require the 
construction of a greenhouse or some other way of confining the space 
you wish to treat. That will  retard the CO2 diffusion into the 
atmosphere while it is sealed, so you will need to design doors and 
other openings to limit diffusion when they are opened, which could 
only be for brief periods. Then you are going to have to find some 
way of monitoring the CO2 levels inside the enclosure to ensure you 
don't poison yourself or anyone else entering the enclosure.

It can be done. It will cost more than it's worth for what you want. 
It will require constant vigilance if someone isn't going to be 
injured.

Bottom line: forget it - it's not worth it.

David Aiken