OK, I found a really cool tool for those industrial growers who need a large amount of C02 for free. They are called rocket mass stoves, and they burn wood efficiently enough to yield only steam and C02 with a slight smokey smell. They have been used for other types of greenhouses before with great success, and they can heat your greenhouse also depending on how you arrange the thermal mass. The best part is, that they use many times less firewood for the same amount of heating as a regular wood stove. I wrote an article on my blog that describes how these things work from a growers point of view. IDK if I am allowed to do this, but here is a link:
http://hubpages.com/hub/Growing-With-Rocket-Stoves
Enjoy.
http://hubpages.com/hub/Growing-With-Rocket-Stoves
Enjoy.