Materials Take Wing

In July 1999, textile engineer Brian George of Philadelphia University’s School of Textiles and Materials Technology visited a friend who raises chickens. After helping with the slaughter, George suddenly realized that he and his friend had a lot of feathers on their hands–and nothing much to do with them. “It seemed like a waste,” he recalls.

In fact, George discovered, his friend’s chicken farm is only a small part of a much larger problem. The poultry industry in the United States alone produces 2 to 4 billion pounds of feathers each year. Chicken- and turkey-processing companies have two main options: They can either sell the feathers for a low price to producers of poultry and cattle feed or pay to send them to landfills.

George wondered what else might be done. He quickly found that other researchers had been thinking about the same thing. Just a couple of days after his trip to the chicken farm, the Philadelphia scientist listened to a Department of Agriculture researcher talk at a scientific meeting. Walter F. Schmidt spoke about the potential of transforming components of feathers into useful products. The challenge is separating a feather’s quill–the shaft–from its barbs, the fibers extending from the quill.

Feathers’ quills and fibers are both made of the protein keratin, the stuff of hair, nails, and wool. But the quill is hard and has a disorganized microscopic structure, while the fibers are soft and posses a very orderly microstructure. Even finely chopped mixtures of whole feathers contain annoying chunks of quill, so they’re difficult to work into products such as paper, cloth, or insulation.

Hungry farm animals don’t seem to mind the grit, but the global market for raw animal byproducts as feed has been decreasing. Scientists suspect that mad cow disease spread when farmers fed infected animal byproducts to cattle.

Any solution to the feather problem demands a convenient way to separate quills and fibers. Schmidt and his colleagues at the United States Department of Agriculture’s Agricultural Research Service in Beltsville, Md., recently developed an instrument for stripping a feather’s quill of its fibrous barbs.

It’s a contraption much like a paper shredder but a “high-precision shredder,” says Schmidt. Now, with pilot plants starting to use this technology to produce pure fibers and pure quill material, researchers have begun looking for novel uses for the fowl product.

Feather shredder and beyond

The USDA instrument lines up feathers and cuts them parallel to the quills, stripping the fibers off essentially undamaged. Then, to separate the light fibers from the heavier quills, the researchers put the mixture through a turbulent airflow. The fibers float up, and the quills drop down.

Before the shredding begins, the USDA technique sanitizes the feathers, which can arrive from processing plants coated in poultry saliva, oils, and dirt.

The cleaning solution–70 percent ethanol in water–sterilizes the feathers, says Schmidt. “You get pristine, clean feathers coming out,” he says.

According to Schmidt, the alcohol solution has benefits over other cleaners.

The solution isn’t hazardous, and less water is required to rinse alcohol off the feathers than to remove detergent. Also, the ethanol can be distilled and reused.

Three companies–Featherfiber Corp. of Nixa, Mo., Maxim of Pasadena, Calif., and Tyson Foods, of Springdale, Ark.–have licensed the new technology from the USDA and are already sending samples of their products to materials scientists around the world.

In some of their first experiments with feathers, George and his students twisted 1-to-2-inch-long turkey-feather fibers with nylon to make yarns, which they knitted into fabrics. In strength tests, the yarn was weaker than pure nylon, but the fabrics insulated better than nylon cloth, says George. Such turkey-based fabric might provide insulation in jackets or sleeping bags, he says. He reported some of that work last November in Boston at the fall meeting of the Materials Research Society.

Now, George’s team is transforming turkey-feather fibers into nonwoven, degradable mats for erosion control in construction sites and other locations.

The researchers use a common textile instrument that blows the feather material into a fragile, half-inch-thick mat that’s loosely held together by friction between the fibers. Then, the scientists strengthen each 36-by-20-inch mat by spraying biodegradable latex on each side.

George and his colleagues are testing the mats on the university campus to see how long they take to degrade and what effect they have on soil. Although the feathers have been sanitized, George wants to be sure there are no lingering microorganisms on the feathers that might leach into the ground.

Also, he suspects that the feather protein might enrich the soil and boost the growth of vegetation that holds soil in place. Currently, erosion-prevention mats are made from more expensive, woven coconut fibers or from wood chips held together with nylon webbing, he says.

In pursuit of a new insulation material, Roy Broughton of Auburn University in Alabama has made nonwoven feather-fiber materials in a different way. Instead of spraying on latex after forming fiber sheets, Broughton mixes synthetic fibers with the feather material and then forms the combination into 2-to-4-inch-thick sheets. When he heats these sheets, the synthetic material partially melts and holds the feather fibers in place.

The resulting combination insulates well and holds its shape better than down does, he says. Broughton suggests that feather insulation could prove useful in comforters and even attics and walls. However, to his knowledge, no one has done flammability tests on the material.

Feather fibers might also find a use in water filters. Manoranjan Misra of the University of Nevada at Reno proposes that this application won’t only help solve the waste-feather problem, but it might also produce better water filters than today’s common filters, such as those made of activated carbon.

The microstructure of feather fibers attracts and traps hard-to-remove contaminants such as uranium, which can threaten water sources in parts of the United States, and other heavy metals, he says.

Before putting the fiber in a filter, Misra “activates” it with ultrasound to open up additional microscopic pores in the fiber’s structure, he says. He’s constructed prototype feather-fiber water filters by packing the fibers into plastic columns. Tests so far, he reports, indicate that the feather filters can remove contaminants from home drinking water or industrial waste. Like George, Misra discussed his work last November at the Materials Research Society meeting.

In laboratory experiments, Misra has found that feather fiber also readily absorbs nuclear byproducts such as radioactive strontium and cesium. He is consulting with Oak Ridge National Laboratory in Tennessee about using his feather-fiber materials to absorb, transport, and store nuclear waste in convenient, small packages, thereby having one waste substance clean up another.

Processed feather barbs could be useful in many more products. Featherfiber, for example, is sponsoring researchers who are creating and testing feather-plastic composites that may provide semirigid surfaces on the interiors of cars, trucks, and airplanes, says company founder David Emery. Other researchers are working on prototypes of a termite-proof material for replacing wood and insulation.

To demonstrate further possibilities, Schmidt and his USDA colleagues have made prototypes of many feather-fiber-containing products including paper, disposable diapers, and clothing. One benefit of making sheets of paper from feather fibers instead of wood fiber, Schmidt notes, is that no bleaching chemicals are needed. Chickens and turkeys have been bred to have white feathers.

The potential for such products’ reducing the overabundance of waste feathers is obvious, says Schmidt. If just 15 percent of the diapers produced each year included feather batting, all the feathers from the U.S. poultry industry could be consumed, he notes. Those same feathers could otherwise be taken up if only 1 to 2 percent of paper were made from feathers instead of wood fiber.

Flights of fancy

Attila Pavlath finds value in feathers’ quills–not just their fibers. Pavlath, a chemist at the Agricultural Research Service’s Western Regional Research Center in Albany, Calif., has been exploring ways to make biodegradable films from agricultural sources that are currently considered waste. Feathers fit the bill, he says: ” We have a large amount, but we don’t know what to use them for.”

Pavlath and his colleagues have found that if they treat powdered feather quills with sodium sulfite, the keratin softens and can be stretched into a translucent film. That chemical process is similar to what a hair-styling perm does. It breaks sulfur-sulfur bonds in protein, which then reconnect in a different arrangement (SN: 8/25/01, p. 124: Chemistry of Colors and Curls). When the researchers incorporate additional proteins, such as those found in wheat or corn, into the film, it becomes more pliable, Pavlath adds.

Currently, a protein film from feather keratin probably costs too much for commercial sale as a plastic wrap for food, says Pavlath. However, the material might have an immediate use in the flexible rings that hold together six-packs of soda or beer. The extra cost would be a scant half cent more per pack, he suggests, but the environmental benefit would be great. The current synthetic rings can take 200 years to biodegrade, and they sometimes harm small animals–especially fish and birds–that get tangled in them, he says. In contrast, a ring that Pavlath has made out of feather keratin and other natural proteins takes just 10 to 12 days to biodegrade.

How feathers–either quills or barbs–will be used commercially is ultimately a matter of economics, says Schmidt. Perhaps high-priced specialty products, such as filters for heavy metals and nuclear waste, will be the destination for the feathers that pile up at poultry farms. Or maybe their fate will be something more mundane but ubiquitous, such as insulation or a ring for beer cans. Though researchers are exploring the possibilities, the future of feathers is still up in the air.