Hey SC Your post is a little confusing but I'll give it a shot...

Co2 never goes bad or stale..it is simply diluted or converted by your plants into O2.
You are in a pretty good position if you need heat. Co2 burner for sure. I was just looking into a natural gas unit for when I get a greenhouse. I would love to tap off my utility gas line and not have to go to the store to get refills.

here is a link I was just reading into. i like the remote burner scenerio...

Peace friend...http://www.hydroponicequipment.com/infopages/co2.shtml