In 2018 cafes across Europe and North America ran short of oat milk, a product whose commercial form came out of Lund University in Sweden in the early 1990s. Food scientist Rickard Oste was studying lactose intolerance and sustainable food, chose oats because they were abundant locally, and founded Oatly. The hard part was physics: oats are 50 to 60 percent starch, and heating a slurry for shelf life turns it into porridge. Alpha and beta amylase enzymes cut those long starch chains into shorter pieces that stay liquid, and homogenization and hydrocolloids then give the drink its creamy, stable body.

That pre-digestion has a cost. A cup of oat milk has about 120 calories, 3 grams of protein, and a glycemic index of 60, against whole milk’s 149 calories, nearly 8 grams of protein, and an index of 47, and it depends on added calcium and vitamins. Oat milk won on performance and footprint instead. Oatly first courted baristas, since it steams with less effort and does not curdle in acidic espresso, and a 200 gram glass takes about 9 liters of water compared with 74 for almond and 131 for dairy.

• A glass of cow’s milk generates about 0.62 kilograms of emissions, against 0.19 for oat milk.
• US retail oat milk sales went from $4.4 million in 2017 to $213 million in 2020.
• Oatly listed on the Nasdaq on May 20, 2021, at a valuation of $13 billion.
• The global oat milk market was valued at $3.7 billion in 2023.
• Oatly sold 141 million liters in the third quarter of 2024 alone.