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Re: Aquatic Plants Digest V4 #256

David Aiken <d.aiken at eis_net.au> wrote:

> 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

It's doable though. A few weeks ago PBS aired a Nova documentary about
global warming, greenhouse effect, etc, that showed an experiment that
addresses excess levels of CO2 over forests. They keep an entire forest
of several acres under excess CO2 by pumping gas from huge generators run
24/7. The gas is piped and diffused at ground level. People walk around 
apparently with no concern about the extra CO2 they breathe. The thing 
exists for a few years, as far as I recall, and they do measure increased
carbon intake and storage and such things. Unfortunately I cannot recall
*where* it is, Washington state perhaps ? I don't recall either what the
cost of the operation is...

- Ivo Busko
  Baltimore, MD