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I am wondering about a specific carbon footprint comparison (i.e. total global warming potential per litre) between soy milk and cow's milk.

This would of course depend on where and how they are produced, but I'd like to know if people have sources that could potentially be gathered (or an article that already did a meta-analysis of some sort!) to have a general idea of the order of magnitude of the difference.

Related question: Which is more sustainable: almond, soy, coconut, cashew or other milk?

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  • Cows emit a bit of CO2.
    – paparazzo
    Sep 24, 2018 at 21:32
  • @paparazzo they produce a lot of CO2-equivalent, yes, and I suspect that enteric emissions from the cow's gut (CH4) would be the main source of a potential difference between the two kinds of milk here.
    – stragu
    Sep 26, 2018 at 10:13
  • Carbon footprint and global footprint are rather different... and yes, means of production has a massive difference as sustainability.stackexchange.com/questions/6843/… the location of production and also the location of consumption. So whilst figures exist, they probably do not represent the optima that are possible (which I'm guessing you are hoping for).
    – George of all trades
    Oct 8, 2018 at 14:14
  • Another problem is that soy milk and cow's milk are not the same. So you then have to consider what are the nutritional aspects that are important to your scenario. Is is it simply calories? Is it protein? If so which ones? And so on... It is also easy to forget the immediate impact on biodiversity, soil structure and so on. Cows are a lot easier to integrate into soil-conserving systems than soy.
    – George of all trades
    Oct 8, 2018 at 14:15
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    Not to hand, but essentially extensively reared cattle can graze on a range of swards. These can be tailored to sequester carbon. Soy as an annual crop is difficult to integrate with perennials and carbon sequestration predominantly occurs through the root systems of perennials. Furthermore, tillage-based agriculture leads to oxidation of soil carbon. Granted there are no-till systems, but permanent grasslands are better at sequestering carbon.
    – George of all trades
    Oct 10, 2018 at 12:15

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Tesco (a large UK supermarket chain) have carbon footprinted a large number of their products - https://www.tescoplc.com/assets/files/cms/Tesco_Product_Carbon_Footprints_Summary(1).pdf. For fresh milk and soya milk these figures were certified by the Carbon Trust. The numbers they give are:

  • Fresh milk average 1.42 kgCO2e/l (range: 1.23 - 1.58)
  • Soya milk average 0.95 kgCO2e/l (range: 0.7-1.4)

The highest values for soya milk are for the sweetened versions; the unsweetened products are at the lower end of the range. For milk, skimmed milk had the lowest and whole milk the highest CO2e.

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    Curious that whole milk would have a higher GWP, since that's the way it comes out of the cow, whereas skim milk requires additional processing.
    – LShaver ♦
    Oct 2, 2018 at 16:10
  • Replying to LShaver: I think the difference is that skimmed milk is only part of the product, so the GWP for whole milk (plus the GWP of the additional processing) gets split between skimmed milk and the cream that is taken off. I expect that the additional processing does not add much, as it is a simple mechanical operation.
    – M Juckes
    Jan 1, 2020 at 11:23
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Ripple Foods, the California-based producers of non-dairy milks made from pea protein, commissioned a Life Cycle Analysis of different milk products that included both soy milk and cow/dairy milk.

They concluded that soy milk has a smaller carbon footprint than dairy milk.

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Source: https://www.ripplefoods.com/pdf/Ripple_LCA_Report.pdf

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