Hey DX,
Thanks for your kind reply!! The purpose of this project was to create a low budget, open-source controller which could be used all over the world so people could improve their crop yield and have more money to spend on other things other then food...
Though this project is still in it's infancy I hope one day it will be used by many people.
And off course I'm interested to see your code so you'll soon get a pm from me 
The screen shots from your web interface look very promising, though implementing CO2 wasn't initially in my plan. I looked it up for some idea's about it and one could build a CO2 generator for a very low budget...So thanks for pointing this out to me 
Will be looking out for some cheap CO2 sensors out there...
With kind regards,
Billie