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.
America’s appetite for Greek yogurt generates tons of acid whey—the yellowish liquid left over after straining or centrifuging yogurt—every year. About two-thirds of the milk used to make Greek yogurt ends up as this by-product. Acid whey can’t be poured down the drain because it is high in nutrients that would fertilize nearby waters, leading to algal blooms and depleted oxygen levels. For years, companies have paid farmers to spread the waste on land as fertilizer or feed it to livestock. But when the popularity of Greek yogurt skyrocketed in the U.S. a few years ago, yogurt makers began working with dairy scientists to develop more economical ways to get rid of their acid whey. Some companies now treat their whey in anaerobic digesters, which produce methane for electricity. Others are working to extract valuable food ingredients such as lactose from acid whey.
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.
In some cases, companies are also investing in anaerobic digesters that rely on microbes to break down acid whey into methane that can be used to generate electricity. Other companies have installed reverse-osmosis filtration systems to remove water from the acid whey, leaving behind a more condensed product that is easier to transport and can potentially be incorporated into other foods.
Work is also underway to turn yogurt acid whey into animal feed and industrial-grade ethanol. At least one company has also developed a process in which proteins derived from milk are added to acid whey to produce a variety of dairy products.
Acid whey contains smaller amounts of proteins when compared with sweet whey, which is leftover from making hard cheeses. But acid whey contains significant amounts of lactose, galactose, calcium phosphate, and lactic acid, “all of which potentially have value and uses in the food industry,” says Dean Sommer, a food and cheese technologist at the Center for Dairy Research at the University of Wisconsin, Madison.
The center has been working with yogurt companies and independently over the past few years to turn acid whey into prototype food products that have significant nutritional value, such as a concentrated sweetener with soluble calcium. “Our goal was to take acid whey, which is mostly considered a waste product, and use modern dairy processing equipment and techniques to fractionate potentially valuable products,” Sommer says.
The center has demonstrated the ability to concentrate lactose in Greek yogurt acid whey using a nanofiltration system. The approach can boost the amount of lactose in acid whey on a dry content basis from 55–65% to as much as 80%, making it comparable to the amount of lactose in sweet whey. The method works by reducing levels of other solids in the whey, including salt, galactose, and lactic acid. Acid whey that has been processed with the nanofiltration system has potential for use as a sweetener. It can also produce lactose and calcium phosphate, also known as milk minerals, both of which can be incorporated into other food products, the center notes in a document developed for the dairy industry.
Other scientists are using enzyme-based approaches to extract protein and lactose from acid whey. Jones Laffin Co., a firm specializing in innovations for the food industry, partnered with researchers at the U.S. Department of Agriculture in 2012 to conduct some of that work.
“Although we have had some success in extracting measurable amounts, we have not reached our goal in reclaiming the enzymes, which makes the process economically viable for commercial use,” Alvin Jones, chief executive officer of the firm, tells C&EN. “However, we recently tested an alternative method that we think has merit.” Jones would not disclose details about that new method.
In the meantime, the company is also considering a filtration system that can be used to treat acid whey. It intends to decide about that technology by the end of February, Jones says.
Some yogurt makers have already adopted whey filtration systems. Chobani installed reverse-osmosis filtration technology at its Twin Falls, Idaho, plant in late 2014. The system “uses pressure to separate water from the whey, leaving a more condensed by-product,” the company says. “The resulting whey can be transported from the plant using fewer trucks than previously required.”
Chobani still delivers whey from its Idaho and New York plants “for supplemental feed and land-applied fertilizer to our local farms,” the company tells C&EN.
“We’re super passionate about our commitment to the environment and our community, and we’ll continue to actively implement sustainability practices in both of our plants,” the company says. “The farms that receive whey from our facilities are required to have a nutrient management plan on file with the appropriate local, regional, and state agencies.”
Dannon, which makes Oikos Greek yogurt, did not respond to requests for information about how it gets rid of acid whey. The company did, however, file a patent application in 2016 related to boosting and stabilizing the lactose content of acid whey. The application suggests that the company has been working on recovering food-grade lactose from yogurt whey. This would be in line with the company’s 2013 pledge to “improve the usage of whey from a nutritional and environmental perspective.”
Other yogurt makers are turning to microbes in anaerobic digesters to convert acid whey into methane, which can be used to generate electricity.
FAGE, an international yogurt company with roots in Greece, invested $20 million in a pretreatment whey facility in 2013 at its Johnstown, N.Y., plant. Whey from the company’s yogurt plant is pumped less than a mile to the facility, where it is treated in an anaerobic digester. Microbes break down the whey, generating methane. The gas fuels three 350-kW generators, which supply more power than the pretreatment facility can use. FAGE sells the excess electricity to the power grid.
More recently, FAGE worked out a deal with Johnstown Renewables. The renewable energy firm plans to make animal feed and ethanol for industrial uses from FAGE’s whey. In 2015, the firm received a $2.9 million economic development grant from the state of New York to build its multi-million-dollar facility near the FAGE plant. Construction began in July 2016 and is in progress.
Back at Yoplait’s Murfreesboro plant, the company, which is owned by General Mills, invested in an anaerobic digester at its wastewater pretreatment facility. In late 2015, the plant stopped hauling its whey to farmers and began sending the liquid down the drains with the rest of its wastewater. That wastewater gets pretreated in the anaerobic digester before it enters the public sewage system. Microbes in the anaerobic digester break down the organic materials in the whey, generating methane that provides 10% (1.6 MW) of the plant’s electricity.
General Mills filed a patent application in 2013 that indicates the company is developing an enzyme-based approach for converting lactose or galactose in yogurt whey into oligosaccharide soluble fiber. This fiber can be added to baked goods, cereals, fruit snacks, and other products. It serves as a prebiotic, a substance that escapes digestion in the small intestine and promotes the growth of beneficial bacteria in the colon.
Also in 2013, General Mills filed patent applications for neutralizing the pH of yogurt whey to form a whey concentrate and for incorporating the whey concentrate into a wide range of food products. The whey concentrate can be used as “a bulking agent, sweetening agent, or a mineral fortificant (calcium and phosphorus) for food products,” General Mills says in the patent application.
The company is also working closely with Quebec-based Ultima Foods. Under a seven-year agreement finalized late last year, Ultima Foods will produce yogurt for General Mills’ Canadian business. Ultima Foods, which makes the iögo Greko brand of yogurt, claims that its ultrafiltration process produces creamy, smooth Greek yogurt without any acid whey by-product. iögo Greko yogurt also boasts higher calcium levels than other Greek yogurts.
Meanwhile, Arla Foods Ingredients, a global company with headquarters in Denmark that specializes in food ingredients made from whey, has developed a unique application for acid whey. The company markets a range of solutions that rely on its Nutrilac whey protein, which is derived from milk. The Nutrilac can be added to acid whey to transform it into nutritious dairy products, including cream cheese, processed cheese, dips, beverages, yogurts, and desserts, the company says.
“Acid whey remains an untapped gold mine,” says Claus Andersen, category and application manager at Arla Foods Ingredients. “It contains the same minerals as milk, which means it offers the same benefits to bones, teeth, and general health.”
Arla Foods Ingredients is promoting profitable use of acid whey under a campaign called Maximum Yield. The campaign’s goal is to raise awareness of the potential value of acid whey and how yogurt companies can use it to increase profits and reduce their waste.
Acid whey “is an exceptional raw material, but many processors don’t know how to unlock its potential,” Andersen says. “We can show dairies just how easy it is.”
CORRECTION: This article was updated on Feb. 13, 2017, to reflect that bacteria do not generate methane in anaerobic digesters. Methanogenic archaea produce the methane.