AskPablo: CO2 from Beer

duff.jpgHave you ever wondered about the carbon emissions generated from making your favorite brewsky, bottle of vino, or 15 year-old Talisker Scotch? Never mind the impact from producing the bottles, shipping the product, or the farm impact–I’ve written about those before (See: AskPablo: Exotic Bottled Water, AskPablo: Glass vs. PET Bottles, and AskPablo: Foodmiles) But what about the fermentation process? That is what we will explore this week on AskPablo.

Alcohol is the result of a fermentation process in which sugars are eaten by small yeast critters which then metabolize it, pee alcohol, and fart CO2. No, it doesn’t sound too appetizing, but it’s the truth…The amount of alcohol depends on the amount of sugar available. In beverages that contain higher levels of alcohol, some of the water has been removed through distillation. So, if your drink of choice is Scotch, Vodka, or Gin, you can add some more CO2 emissions from the operation of the distillery. Of course, distilled alcohol is more concentrated, which means less packaging and less shipping emissions per unit of beverage when compared to beer or wine.
Sugar content in the original, unfermented batch is measured in units called “brix.” Brix is a ratio between the weight of the sucrose (sugar) in the solution and the weight of the solution itself. So 10 g of sucrose in 100 g of solution would have a brix value of 10. There is a direct correlation between brix and specific gravity, which is more commonly used in brewing. Beer is typically between 5 and 15 brix, depending on the desired final alcohol content. Grape juice used in wine making is between 22 and 30 brix. The reason brix is important to us is that it tells us how many grams of sugar are going to be converted into alcohol and CO2 per 100 grams of solution.
Let’s say that our favorite brew has a brix of 12, or 12 g of sucrose per 100 g of solution. We can ignore the water, which is 88% of the solution. The glucose molecule (C6H12O6) has a molecular weight of 180.16 g/mol and, when metabolized by the yeast, becomes 2 ethanol molecules (CH3CH2OH) and 2 carbon dioxide molecules (CO2). A CO2 molecule has a molecular weight of 44.0095 g/mol. So the conversion ratio between the sugar and the CO2 is 48.8% ((44×2)/180). This means that the amount of sugar (12 g) times the conversion ratio (48.8%) equals the amount of CO2 produced per 100 g of solution. In this case it comes out to 5.856 g of CO2.
Keep in mind that this CO2 production actually reduces the amount of the solution. So, per final 100 g of beer, we need to create 6.22 g of CO2 (5.856/(100-5.856)x100). This is 62.2 g of CO2 per liter of beer. Maybe this doesn’t sound like much, but let me put it in perspective: in 2004, Americans drank 23.974 billion liters of beer, resulting in 1,491,182 mT of CO2 emissions. Global beer consumption in 2004 was 150.392 billion liters, resulting in 9,354,382 mT of CO2 emissions. For a little something more to think about, the US emitted a total of 1,446,777,000 mT of CO2 in 1996. Now, keep in mind that this is based on an assumption of a brix value of 12. The average beer may be a bit weaker than that. Feel free to plug in your own assumptions to see what you get. Either way, the CO2 emissions from brewing are not negligible. We probably haven’t heard much about it since it is the result of a natural process and not the burning of a fossil fuel. But CO2 is CO2…
Pablo Päster, MBA
Sustainability Engineer

11 responses

  1. One other point in favor of beer is that it is a renewable resource (Yay beer!). The carbon emissions are part of a natural cycle.
    The British Beer & Pub Association quotes that “The amount of carbon dioxide released during fermentation is roughly a quarter of the amount absorbed from the atmosphere through photosynthesis by the growing grain.”.
    Now, who would not trust a beer an pub association for their word?

  2. Any data on CO2 emmissions from winemaking? and… shall we start compensating also for emmissions other that from burning fossil fuels (apart from breathing…)
    Any comments from any Wine Association?

  3. Interesting!
    Homer Simpson would be very angry. Plus if there was no beer, what would I drink while driving my H2 around.

  4. All of this CO2 is from grain which is grown on an annual basis, meaning that there is no net C02 produced by this process. If beer were made from oil, this would be a concern…otherwise it is like calculating your CO2 footprint on your compost.

  5. Yes, but most breweries of any size have CO2 recovery plants in house that capture and re-use this by product for the carbonation process. It is misleading to imply that all the CO2 produced during fermentation becomes an emission to the atmosphere.

  6. What is the world-wide annual production of alcohol? Can one determine from this how much CO2 was created in its production? Then what is the percentage of this fermentation CO2 to the total annual man-produced CO2?

    Knowing the effect of my martinis on the environment may help me to cut back.

    Or if the amount of CO2 is trivial in comparison to the total, I won’t cut back.

    Don Pooley

    p.s. And how about carbonated soft drinks?

  7. I believe that carbon monoxide (CO) is much worse than carbon dioxide (CO2). Pine trees contribute to the CO in my area, and they provide much greater tax incintives…

  8. well everyone is thinking about CO2 no-one is really caring about our holy beer that really :(

    well if 62.2 gms of mass is missing from beer in the form of Co2 from 1 lts then i think its a lot of fun that we missing :P
    ok now on theory
    we r having 2-3% v/v of co2 is dissolved in the beer itself.
    plus almost all that Co2 that is produced by the beer or any fermentation industry is recovered by the co2 recovery system and filtered and that co2 is reused for some process.

  9. Only in the Bay area would someone with a business degree claim to be a “Sustainability Engineer”. You’ll forgive me if I disregard this wholesale.  

  10. For the people that think a beer factory has a C02 recovery system, you do realize that much of the C02 is released when the beer is open and drunk, right?  Same with soda.  But you don’t care, you just care about getting rid of the internal combustion engine.

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