CO2

They give off too much carbon dioxide, for one thing.

And part of the process has the potential to cut carbon dioxide as well.

"Perhaps they are not taking enough carbon dioxide out of the air?"

Some of this carbon dioxide is also taken up in different ways.

What would happen if you took carbon dioxide out of this?

Well let's take carbon dioxide out of that and what do you get?

But carbon dioxide was off the table, for two main reasons.

Carbon dioxide would be responsible for 50 to 55 percent.

Okay so we get the carbon dioxide given off and name two products.

"If you don't do anything, carbon dioxide will be 15 to 20 percent above 1990 levels" by 2000.