There's a lot of talk these days about individual carbon footprints, CO2 in the air, and global warming.

Knowing that our little friends the yeasts exist basically to turn sugars into CO2 and alcohol, I'm wondering just how much of the gas a 5-gallon batch adds to the atmosphere and how it compares to other common activities that create CO2.

I'd also be interested in finding more information about how to calculate a total carbon footprint for a batch, including information about the differences between grain types and the amount of resources it takes to grow them, how heating elements vs. propane effect carbon usage, etc.

  • 1
    Check out purposeenergy.com They are creating a technology that harvests methane from spent grain. They are currently building a 2 Billion BTU plant at the Magic Hat brewery in VT; they'll use the brewery's waste to power the brewery.
    – G__
    Nov 17, 2010 at 17:32
  • You are trying to reduce a factor that is so small it makes no difference. Their are much bigger pollution problems that you should be worrying about. Such as using glass. Its takes a lot of energy to make and is usually just discarded after. Nov 17, 2010 at 21:39

2 Answers 2


Don't worry about the CO2 from the fermentation. That was recently CO2 in the atmosphere anyways. See, the barley plant used it to make the barley seed. Then you made the barley seed into wort. And the yeast made the wort into CO2 (and beer!). As Disney taught us, its the circle of life!

Now your heating method for your kettle? That's a different issue. Depends on where your energy source comes from. Fossil fuels? Yep. That's a carbon footprint. Solar or wind. Negative sir!


Just to also point out. Propane is about the least efficient, highest cost, and biggest CO2 footprint you can possibly have in brewing. Unfortunately for most, it is also the easiest way to start.

  • Solar and Wind still have a carbon footprint. What type of energy do you think they use to make solar and wind generators? Nov 17, 2010 at 21:37
  • 1
    Only renewable energy. They started with one windmill built by hand, and have created every other solar and wind generator from the original or ones created from the original.
    – PMV
    Nov 18, 2010 at 15:27
  • Water wheels made from hand sawn wood? Oh, I forgot they had to make the saw and it had a carbon footprint... =) Nov 19, 2010 at 15:31
  • 1
    While it's true that the CO2 from fermentation came from the atmosphere, I think it still counts as CO2 emissions. If you burn wood you produce CO2 emissions, even though the tree absorbed it. In fact, the carbon in fossil fuels was originally in the atmosphere, before it was absorbed by plants and algae, decomposed, pressurized for millennia, and finally drilled for commercial use.
    – Hank
    Jun 14, 2012 at 18:27

If you happen to have a room with a lot of plants, put your fermenter in there, they'll love it, and convert the CO2 back to O2.

  • It's what I do. I try to have the number of active fermenters is less than or equal to the number of houseplants I have in my home. Maybe I should go for greater than 2 plants per fermentor.
    – Pulsehead
    Nov 18, 2010 at 13:35

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