CO2 footprint: plant milk vs. cow's milk

Plant milk is better for the environment than cow's milk. You hear that often, but how big is the difference really? And does it matter which plant milk you choose?

Short answer: the difference is significant. Long answer: it depends on what you look at. CO2 emissions aren't the whole story.

The numbers

The most well-known study on this is by Poore and Nemecek, published in Science in 2018. They analyzed the environmental impact of thousands of food producers worldwide and looked at three things: CO2 emissions, land use, and water consumption.

Milk type	CO2 (kg/liter)	Land (m²/liter)	Water (liters)
Cow's milk	3.2	9.0	628
Oat milk	0.9	0.8	48
Soy milk	1.0	0.7	28
Almond milk	0.7	0.5	371
Rice milk	1.2	0.3	270

Source: Poore & Nemecek (2018), Science

What stands out?

The differences between milk types are bigger than you might expect.

• Cow's milk scores worst on all fronts. The 3.2 kg CO2 per liter comes from two major sources: the cows themselves (which emit methane) and the production of feed. Both are roughly equally important. The high land use is for pastures and feed crops. And the water consumption? Cows drink a lot, and the crops for their feed need irrigation.
• Oat milk is the all-rounder. Low CO2 emissions, little land use, and by far the least water. Oats grow well in temperate climates and need hardly any irrigation. That makes oat milk the most sustainable choice if you look at the overall picture.
• Almond milk has a water problem. In terms of CO2 and land use it scores well, but the water footprint is high: 371 liters per liter of milk. Almonds are mainly grown in California, where water is scarce. Each almond costs an average of 12 liters of water. In areas with water scarcity, that's problematic.
• Soy milk scores well overall. Caveat: pay attention to origin. Soy from South America is often linked to deforestation of the Amazon rainforest. Locally grown soy is more sustainable.

The difference in perspective

Cow's milk: 3.2 kg CO2 per liter. Oat milk: 0.9 kg. That's a factor of 3.5. Sounds abstract, but here's a quick calculation:

Say you drink 3 liters of milk per week. That's 156 liters per year. With cow's milk that's 499 kg CO2. With oat milk that's 140 kg CO2. The difference: 359 kg CO2 per year, per person, just by switching milk types.

For comparison: a short flight of 1,000-1,500 km emits about 200-300 kg CO2 per passenger. Switching from cow's milk to oat milk saves more than one such flight per year.

A point that's often forgotten: the carton packaging. That also has an environmental impact. But compared to the production of the milk itself, it's relatively small: estimates vary, but it's a fraction of the total footprint.

Want to reduce the packaging impact further? Then making it yourself is an option.

Making yourself: even more sustainable

If you make plant milk yourself, you eliminate packaging and transport. You buy oats in bulk or in a paper bag, add tap water, and done.

The CO2 footprint of homemade oat milk is even lower than the 0.9 kg from the table, because those figures are based on commercial production including factory and distribution.

A milk machine like Mylky uses little electricity per liter of milk: the process only takes a minute. The environmental gain lies mainly in what you don't do: no buying cartons, no trucks delivering, no packaging that needs recycling.

Still some nuance

A few notes on these numbers.

• They're averages. An organic farmer who lets his cows graze has a different footprint than a mega-farm. The same applies to plant milk: locally grown oats are more sustainable than imported almonds from California.
• Nutritional value also counts. Cow's milk contains more protein than most plant-based alternatives. If you compensate by eating more or taking supplements, the calculation changes somewhat. But even then, plant milk remains more sustainable.
• It's not all about CO2. Biodiversity, soil health, animal welfare: also factors that count. They're harder to quantify, but no less relevant. Dairy farming has more impact on all these points than plant-based alternatives.

The conclusion

If you look purely at environmental impact, plant milk is almost always better than cow's milk. Oat milk is the most sustainable choice, especially if you also consider water consumption. Almond milk scores less well because of water use.

Making it yourself is even more sustainable: no packaging, no transport. Plus: you know exactly what's in it.