Researchers make biodegradable films from biofuel and dairy byproducts

The search for innovative uses of biofuel byproducts continues. This is crucial to ensure biobased fuels become more commercially viable. Scientists from the U.S. Agricultural Research Service (ARS) announce they have developed biodegradable protective films from combining both dairy and biofuel production residues.

The technology was developed by research leader Peggy M. Tomasula and her colleagues at the ARS Eastern Regional Research Center's Dairy Processing and Products Research Unit in Wyndmoor. They found that combining the milk protein casein with water and glycerol, a byproduct of biodiesel production, produces a water-resistant film that can be used as an edible coating for food products.

Because of increased biodiesel production, glycerol (glycerine) is beginning to flood the market, and urgently needs new uses. For each liter of biodiesel produced, some 10% glycerine is obtained. Researchers are examining its use as a cattle and poultry feed, but also found it makes for a good feedstock for biogas production. It may also be a starting product for the manufacture of green specialty chemicals such as propylene glycol.

Its use as an ingredient in edible bioplastic films is the latest application in this series. To make the films, the scientists used carbon dioxide as an environmentally friendly solvent to isolate dairy proteins from milk, instead of harsh chemicals or acids that can be difficult to dispose of, according to Tomasula. Carbon dioxide (CO2) is another byproduct of the glucose fermentation that is used to make ethanol. Using CO2 makes the edible film more water-resistant and biodegradable.

The resulting food coatings are glossy, transparent and completely edible. Like conventional food packaging, edible films can extend the shelf life of many foods, protect products from damage, prevent exposure to moisture and oxygen and improve appearance. By using renewable resources instead of petrochemicals, the scientists can create more biodegradable products and reduce waste:
biofuels :: energy :: sustainability :: biodiesel :: glycerin :: glycerol :: dairy :: whey :: casein :: bioplastic :: bioeconomy ::

Tomasula has been working with food technologist Kirsten L. Dangaran and chemist Phoebe X. Qi to improve the appearance and protective properties of the casein films.

At one point in the production process, CO2 dissolves into the milk, decreasing its pH level and causing casein to form particles of a substance known as CO2-casein. The researchers found that decreasing the size of the CO2-casein particles improved the films' ability to block moisture and increased their glossiness.

They also found that coating a low-density polyethylene film with the CO2-casein increased the film's ability to block oxygen permeation. Adjustments like these could make the films more competitive with existing, less eco-friendly products.

Bioplastics from whey
Earlier other researchers from the ARS patented a bioplastic production process based on the utilization of whey, the liquid byproduct that remains after curds from cheesemaking coagulate. Whey is used in a range of products such as candy, pasta, baked goods, animal feed—and even pharmaceuticals. Some 1 billion pounds of the byproduct are produced each year in the U.S. alone.

ARS’s Dairy Processing and Products Research Unit at the Eastern Regional Research Center (ERRC) showed that whey can also be used to create eco-friendly products. For example, using a process called 'reactive extrusion', food technologist Charles Onwulata supplements polyethylene—a common nonbiodegradable plastic—with whey proteins.

Reactive extrusion involves forcing plastic material through a heating chamber, where it melts and combines with a chemical agent that strengthens it before it’s molded into a new shape. Onwulata showed that by combining dairy proteins with starch during this process, it’s possible to create a biodegradable plastic product that can be mixed with polyethylene and molded into utensils.

Working with laboratory chief Seiichiro Isobe, of the Japanese National Food Research Institute, Onwulata created a bioplastic blend by combining whey protein isolate, cornstarch, glycerol, cellulose fiber, acetic acid, and the milk protein casein and molded the material into cups. Onwulata observed that dairy-based bioplastics were more pliable than other bioplastics, making them easier to mold.

Bioplastic blends can replace only about 20 percent of the polyethylene in a product, so resulting materials are only partially biodegradable. But Onwulata and his colleagues are currently applying this process to polylactide (PLA), a biodegradable polymer.

“Blending dairy-based bioplastics with PLA could eventually allow producers to make completely biodegradable materials,” he says.

Biofuels from whey
In another development, researchers from Germany announced a while ago they collaborated with a dairy products company to make ethanol from whey, the byproduct of cheese and casein.

This means milk and its byproducts, in combination or not with a biodiesel byproduct, opens up a new series of bioplastics and renewable, green fuels.

Image 1: A continuous biodegradable protein film begins to form using the new ARS film-making process. Photo by Paul Pierlott, USDA-ERRC/VGT.

Image 2: Food technologist Charles Onwulata inspects molded dairy bioplastic made from surplus whey proteins. Photo by Peggy Greb.

More information:
U.S. Dept. of Agriculture, ARS: Edible Films Made From Dairy, Biofuel Byproducts - June 5, 2007.

U.S. Dept. of Agriculture, ARS: Make Whey for Progress New Uses for Dairy Byproducts - June 8, 2007.

U.S. Dept. of Agriculture, ARS: Dairy Byproducts Can Supplement Plastic - May 1, 2007.