Uses for skim milk before it was marketed as a nonfat diet product: Hog slop and wool.

Hog Slop and Turtlenecks: Skim Milk’s Unlikely Transition From Animal Feed to Diet Product

Hog Slop and Turtlenecks: Skim Milk’s Unlikely Transition From Animal Feed to Diet Product

What to eat. What not to eat.
Feb. 2 2014 11:47 PM

Would You Wear a Sweater Made From Milk?

Yeah, people in the ’40s didn’t either.

"Enjoy that refreshing glass of hog slop!"

Photo by Everett Collection/Shutterstock

Excerpted from Pure and Modern Milk: An Environmental History Since 1900 by Kendra Smith-Howard, out now from Oxford University Press.

Do you prefer the lighter flavor of skim milk to 1 percent, 2 percent, or whole? Before World War II, skim milk—a byproduct of butter processing—was not sold in stores, but either discarded or fed to chickens, hogs, and calves as a protein-rich replacement for costlier animal feed. The development of skim milk as an attractive product for sale only came about because dairy producers, emboldened by their success selling milk to Uncle Sam during World War II, seized on postwar marketing opportunities to sell what once had been hog slop to housewives and families.

In the 1920s, the streams in rural areas with cheese factories and creameries festered with rotting dairy discharge. Excess buttermilk spilled from creamery spouts onto adjacent fields and directly into waterways. Ditches brimmed with whey, attracting flies and creating a stinky mess. Many creameries had no access to a city sewer. In 1930, only 17 percent of waste released by Wisconsin milk plants was treated, leaving 42,513 pounds of untreated whey, skim milk, and other byproducts to be drained into the state’s waterways.


The release of skim milk and whey into streams was not a new practice, but changes in the rural economy of the 1920s and 1930s—the rise of automobile tourism and the farm depression—changed the way that industrialists understood and reacted to milk plant pollution. The increase in rural tourism during the interwar period made it more difficult for dairy plants to hide the deleterious effects of dairy manufacturing from the public eye. As the number of Americans with automobiles increased and rural roads improved, motorists sought to take invigorating outdoor adventures in the countryside. When tourists who ventured to the countryside to be energized by fresh breezes found themselves breathing the foul vapors of “dairy air” instead, disappointment ensued. One manager explained in the late 1920s:

The automobile has brought the cheese factory odor and conditions to the attention of countless thousands of people, and no amount of argument or favorable advertising is going to convince the casual traveler that our cheese is of a high quality, when the attending conditions are such as to produce a feeling bordering on nausea.

The dairy industry’s long-standing use of natural scenes and ideals to promote the healthfulness of the product made the degraded landscape surrounding cheese and butter plants especially problematic. Dairy waste undermined the pastoral iconography used to sell dairy foods. The residue also appeared particularly wasteful during a time of economic strife. Ditches brimming with whey and buttermilk signaled the ecologic ills and economic imbalances threatening national prosperity.

Tourism, combined with a new attention to wasted resources in the farm depression, recast a persistent problem with dairy waste as one of national economic significance and by the interwar years, dairy plants began to consider whether they might be able to market dairy residues nationally or even internationally. Managers of cheese plants and butter factories sought to make the substances left over from the cheese- and butter-making processes into consumer goods or industrial materials.

In the 1920s and 1930s, manufacturers first used organic chemistry to remake excess whey, skim milk, and buttermilk into commercial industrial products, hoping to increase returns to farm patrons and eliminate the sanitary and legal problems such wastes generated. The transformation of agricultural byproducts into industrial resources came to be known as chemurgy, a word coined by an organic chemist with Dow Chemical Co. By 1935, 300 scientists, industrialists, and members of farm organizations gathered to form the Farm Chemurgic Council, a group devoted to studying and establishing new nonfood uses for farm crops and markets for agricultural byproducts. Unlike nutritionists, who lauded the balance of proteins, carbohydrates, and fats in milk, chemurgists sought to break down milk into its component parts and find uses for each of them. Chemurgy became a way to reconcile the growing tension between modernity and agrarian tradition.

In the dairy industry, chemurgists were especially interested in the protein of milk, called casein. Extracted from skim milk, the byproduct of butter processing, casein could be integrated into a wide variety of household goods. As early as 1900, Henry E. Alvord reported that casein could substitute for eggs, replace glue in paper sizing, and be hardened into plastic to make buttons, combs, or electrical insulators. During World War I, casein coated airplane wings.