Fifteen tanker trucks full of acid whey, the yellowish liquid by-product of Greek yogurt production, left Yoplait’s plant in Murfreesboro, Tenn., every day in 2014. The trucks headed to nearby farms, where farmers would spread the whey onto their fields as fertilizer. Similar activity on an even larger scale was taking place in New York, where some of the biggest Greek yogurt makers—Chobani, Dannon, and FAGE—have production facilities.
Approximately 771,000 metric tons of Greek yogurt was produced in the U.S. in 2015, representing nearly 40% of the U.S. yogurt market, according to U.S. Department of Agriculture and market research data. In 2004, Greek yogurt made up only 1–2% of the U.S. yogurt market.
As the demand for Greek yogurt skyrocketed, so did the amount of acid whey that manufacturers needed to dispose of. For every kilogram of Greek yogurt produced, 2–3 kg of acid whey are left behind.
Farmers can use only limited amounts of the nutrient-rich liquid. If they put too much of the whey on their land, the mixture will run off into nearby waterways, leading to algal blooms, low levels of dissolved oxygen, and fish kills. What’s more, acid whey can emit a stench when baked in the hot sun, leading neighbors of some farmers to complain about the smell.
As a result, competition is fierce among companies to find an economical way to use acid whey from yogurt. Many companies contacted by C&EN either did not respond or were reluctant to provide information about their work, offering responses such as “it could prove to be a defining trade secret.”
Nonetheless, patent applications and company statements provide details about efforts to handle acid whey. A quick search of global patent applications related to the use of yogurt acid whey was conducted by CAS, a division of the American Chemical Society, which also publishes C&EN. The search revealed more than 3,500 patents, 75% of which were published in the past five years. Much of the work has focused on extracting valuable ingredients, such as proteins and lactose, from acid whey using nanofiltration and other membrane-based filtration processes.