Oat Milk vs. Cow's Milk: Which Is More Environmentally Friendly?

Glass of oat milk on surface with raw oats

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It's often said that oat milk, relatively new to the dairy-free scene, is better for the environment than regular old cow's milk—but why? Is it the water needed to sustain animals versus grow plants? Or the amount of land required? Perhaps it's the methane plumes that cows emit from their mouths and backsides.

Learn all about the environmental impacts of oat milk versus cow's milk and why the former is widely believed to be the all-around greener option.

Environmental Impact of Oat Milk

Oats in a field against a blue sky

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Oat milk was named the second most popular dairy milk alternative, behind almond milk, in 2022. It accounted for 17% of the U.S. plant-based milk market. A 2022 Grand View Research report predicted that global oat milk sales will continue increasing by another 14.2% annually from 2020 to 2028, reaching about $6.5 billion by the end of that period.

Water Use

A gallon of oat milk takes about 48 gallons of water to produce, not including the water added to liquidize the oats during manufacturing (which is about four cups of water to a cup of oats). The crop, Avena sativa, is known to sit at the high end of water use efficiency—not just because it requires so little (17 to 26 inches per growing season) but also because it grows in cool weather.

Growing in the cool season helps oat crops retain moisture and means they can get most of their water from rain, not groundwater reservoirs. A study of average water footprints from 1996 to 2005 found that oats use eight times more green water (rainwater) than blue water (surface or groundwater).

In much of the U.S., the growing season runs from March through July, though seeds can be sowed as early as September.

Land Use

Aerial view of combine harvesting a line of oats

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Oats grow all over the world, from North America to Europe to Australia. They thrive in just about any soil type and tolerate a range of climates. Because their entire growing season lasts only about four months, they also allow for other crops to take over their turf for the remainder of the year. This is called crop rotation, an important principle of regenerative agriculture that keeps soil healthy and pests at bay.

You'll often see oats growing on long, leafy stems—akin to wheat—on the side of the road in the American Midwest. Each acre yields about 2,080 pounds of oats or about 1,700 gallons of oat milk.

Greenhouse Gas Emissions

Grain sorting machine and storage in factory

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Oat milk has a lower carbon footprint than all its top competitors: cow's milk, almond milk, and soy milk. One glass is equivalent to about .4 pounds of carbon dioxide emissions, and that's from seed to milk processing. It seems to be the greenest milk type of all—except for one pitfall.

Unlike cow's milk, oat milk (and all plant-based milks) creates a byproduct that gets wasted in the manufacturing process. The pulp left over after soaking, blending, and straining the oats is sometimes sent to landfills where it produces methane, a greenhouse gas 80 times more potent than carbon dioxide. The good news? It's often repurposed as livestock feed instead.

It's important to purchase locally grown oats when possible, as imported oats have a substantially higher carbon footprint than those grown domestically. Thankfully, this adaptable crop grows in abundance all over the country.

Pesticides and Fertilizers

One major environmental issue plaguing the oat industry is its reliance on synthetic fertilizers and pesticides. These chemicals leach into the soil, into groundwater reservoirs, and wind up running into freshwater systems where they pose serious threats to aquatic life.

"All the chemicals of the industrial water are toxic to all forms of aquatic life ranging from minute organism to giant fishes," Indian researchers wrote in a 2019 handbook. "Among the most prominent pollutants that have rendered aquatic resources polluted and caused huge damage to aquatic organisms are pesticides."

In 2015, a reported 64% of oat crops in the 13 top oat-producing U.S. states were treated with pesticides (herbicides, fungicides, and/or insecticides). About three-fourths were also treated with chemical fertilizers. The best way to avoid oats that have been treated with chemicals is to buy organic.

Environmental Impact of Cow's Milk

Farmer pouring raw milk into container with cows in background

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Cow's milk is the most conventional milk type and the one that still rules the market today. Whereas the most popular alt milk, almond, is worth $6.5 billion globally, cow's milk is worth $827 billion—about 130 times as much. It certainly is still the leading milk type, and perhaps also the most criticized.

Here's a breakdown of dairy milk's environmental impact.

Water Use

Data compiled by Water Footprint Network shows that bovine products require more water per kilogram than sugar crops, vegetables, and fruits combined.

Cow's milk is indisputably the most water-intensive milk type, just one gallon requiring a staggering 628 gallons of water. Cattle drink, on average, 30 to 50 gallons per day.

The good news is that a reported 85% of their water intake comes from rain—green water—while only 8% of it is blue. That percentage varies depending on each farm location's precipitation levels. Cattle farms in Canada have a much lower blue water footprint than those in perpetually parched California, for instance.

Land Use

Aerial shot of milk tanker driving between dairy farms

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Cattle farming has been called the leading cause of deforestation in the Amazon. Vast swaths of this vital rainforest have been cleared to make room not just for cattle farming—although the Brazilian Amazon is home to 40% of the country's cattle, including the world's second largest herd—but also the cattle's primary food source, soy.

The World Wildlife Fund has reported that 80% of the world's soy is used to feed livestock. "Millions of hectares of important habitat like the Amazon rainforest, the Cerrado, the Atlantic Forest, the Gran Chaco and Chiquitano in South America, or the Northern Great Plains of the U.S. are being ploughed up to make room for more soy production," the organization says.

Almost 80% of all agricultural land in the world is dedicated to livestock grazing land and feed crops.

Greenhouse Gas Emissions

Here's the biggest qualm environmentalists have with cow's milk: its emissions. There are nearly a billion cows on the planet, each a living, breathing methane machine whose burps and farts amount to 220 pounds of greenhouse gases per year. Livestock is singularly responsible for 32% of human-caused methane emissions globally.

Just one cup of cow's milk comes in at 1.3 pounds of greenhouse gas emissions, three times higher than any plant-based alternative.

Animal Exploitation

Cows in a line in industrial milking parlor

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While it might not directly impact the environment, the welfare of dairy cows is a big concern for many eco-minded folks. Cows produce an average of 23,400 pounds of milk per year. And that's only if they're impregnated repeatedly, with unnaturally short calving intervals, for several consecutive years.

After they're done producing milk, they are most often handed over to the beef industry—21% of beef sold in the U.S. comes from the dairy sector—usually cutting their 20-some-year lifespans by more than half.

Which Is Greener, Oat Milk or Cow's Milk?

Close-up of person pouring oat milk into bowl of cereal

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The experts are right, of course: Oat milk is the eco-friendlier option when pitted against its traditional cow-derived counterpart. It requires 1,000 fewer gallons of water to make per gallon, emits three times less greenhouse gases, and doesn't fuel deforestation or require millions of animals to be slaughtered in the process.

Columbia University's Climate School calls oat milk the most sustainable milk out there, and cow's milk the least. Sadly, it's slightly less nutritious than dairy, providing half the protein and double the carbohydrates. It can also cost twice as much as dairy milk, which many can't afford.

If you have the means, though, switching form dairy milk to oat milk is good for you (hello, fiber!) and the planet. When buying oat milk, make sure it's made from USDA-certified organic oats, choose brands based in your neck of the woods, opt for the unsweetened variety, and look for ones with calcium and/or vitamin D fortification for extra nutrition.

When it comes to packaging, know which materials are accepted by your curbside recycling service. Many oat milks come in plastic-coated Tetra Pak cartons, which are in most cases only accepted by specialized Tetra Pak affiliates.

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