Walk into any coffee shop and you’ll likely see a long list of available milks — oat, almond, soy, and good old-fashioned dairy, just to name a few.
Taste is obviously a factor that influences many people’s choices. So are costs and dietary restrictions. But another is which milk comes with the lowest environmental impact.
That’s where things can get complicated.
Calculating Foods’ Impact on Nature and Climate
There are multiple ways to calculate a particular food’s impact on the planet. One is its effect on the climate: How many greenhouse gas emissions are associated with its creation — including raising a cow or growing a plant, turning that raw material into a product like milk, then packaging it and shipping it to its point of sale?
Another is water use. Agriculture is responsible for 70% of freshwater withdrawals — but different crops and animals require varying amounts of water to produce, thus carrying different “water footprints.”
Other factors — such as where the food is produced; how much land it needs to grow; and how many pesticides, fertilizers and antibiotics are used in the process — also affect its impact on people and the planet. But unlike nutritional content or costs, emissions, water use and other environmental data aren’t displayed on food labels, making it tricky for consumers to decide what’s best for them.
Digging into the Data on Plant-based vs. Dairy Milks
So what does this mean for the growing number of milks on the market? Digging into the data sheds some light.
I and other researchers looked at the average greenhouse gas emissions and liters of water needed to produce one cup of cow’s milk, as well as soy, almond, oat, pea and coconut milk. (In this case, we analyzed the refrigerated or boxed variety of coconut milk, which is thinner and lower in fat and calories than the canned variety typically used in cooking.) While on average Americans consume more protein than is needed across all meals, milk is often a key ingredient providing protein for satiating breakfasts. Thus, we also compared milks’ relative protein content.
A few key findings emerged:
- Plant-based milks on average generate roughly one-third or less of the greenhouse gas emissions of cow’s milk, and most use considerably less water. This tracks with the data around plant- vs. animal-based proteins in general. For example, beef production requires 20 times the land and produces 20 times as much greenhouse gas emissions per gram of protein than common plant proteins like beans.
- Pea protein milk is a very sustainable choice, producing far fewer emissions and requiring a fraction of the total water1 than most other milks assessed, while rivaling the protein content of cow’s milk. Soy milk is a close second, with relatively low environmental impacts and reasonably high protein content compared to cow’s milk.
- Oat and coconut milks also have lower emissions and water use compared to cow’s milk, but are also relatively low in protein.
- Almond milk is good for the climate, but uses about the same amount of water as cow’s milk and contains very little protein. Notably, the amount and impact of water use varies depending on where and how food is grown, and some places are more water scarce than others. Thus, the impact of almond milk’s water footprint may be worse than cow’s milk if comparing almond milk produced in a water-stressed region such as California with cow’s milk produced in less water-stressed regions. That said, California is the top producer of cow’s milk in the United States, so comparing direct water use footprints is still valid in many cases.
Choosing the Milk that’s Right for You
Many factors influence individual food choices, including cost, taste, dietary restrictions, geographical access and cultural traditions — and all of them are important. The nutritional content of plant-based milks also vary substantially depending on their extent of fortification and whether they include added sugars — key considerations for individual health.
1 While data for pea milk’s blue water footprint isn’t available, its total water footprint is estimated to be 86% lower than that of cow’s milk. The blue water footprint represents surface water withdrawals that are lost to evaporation or incorporated into the product, such as for irrigation; total water footprint includes blue water plus green water (i.e., rainwater) plus grey water (freshwater required to assimilate pollutants, in this case, nitrogen fertilizer runoff, to meet water quality standards).
