There are always wide variations – partly due to the methodologies used, and partly because the difference between the best and worst producers is often huge.
Studies on the emissions of a litre of dairy milk, for example, have come up with answers that vary from 0.54 to 7.50 kgCO2eq.
However, if you look at lots of studies, certain basic patterns emerge and you can get a pretty good overall picture.
Greenhouse gas emissions of plant vs dairy milk
Our bar chart (right) shows average CO2 emissions per litre for various milks within Europe found by one large review study, led by Joseph Poore at the University of Oxford. (The almond figure is the global one as there was no figure for Europe.)
The global average figures from this study were quoted by the BBC, which include a higher figure for cow milk, but we’re giving the European figures as they are more relevant in the UK and also more similar to figures in other reviews.
Although figures differ between reviews, the pattern is basically consistent that cow’s milk is worse than the others, which isn’t that surprising, given the emissions of cows (see our feature on the climate impacts of meat and dairy).
Furthermore, as is mentioned in the feature, most life cycle figures do not include the greenhouse gas ‘opportunity cost’ of land use (the other things that you could do with the land, like reforesting it, that could potentially remove carbon from the air). If you do include that, animal products come out much worse. The ‘land used’ figures in the bar chart show why. (These figures are also from Joseph Poore, and again, for Europe except in the case of almond.) Basically, cow’s milk uses more land per litre than any of these plant milks.