I know this much about fermentation. Yeast consumes simple sugar and changes it into an equal weight of ethanol and CO2 gas. The alcohol stays liquid, and the CO2 bubbles off into the atmosphere.

I'm going fishing today, but when I get back I'll figure something out. What's the weight of a gallon of ethanol? 7 or 8 lbs., I imagine. Whatever that weight is - how much volume does an equal weight of CO2 occupy?

I'll find out, but that's a big bunch of CO2 for every gallon of ethanol made - and that's not counting the additional CO2 that's released when ethanol burns.

You'd think the enviro-wackos would be throwing a fit about that.