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  Science & Technology  
  September 6, 2004
Volume 82, Number 36
pp. 36-39


Chicken feathers are being transformed into films, composites, plastics, and roofing material
POULTRY PLANTER Cut to fit a flowerpot, this mulching film is made entirely of feathers.


For every vacuum-packed, shrink-wrapped pound of chicken in the supermarket, a handful of feathers has been left behind somewhere. Chicken feathers don't weigh much, but when you consider that the U.S. poultry industry produces more than 8 billion broiler chickens every year, those handfuls start to add up.

Rough estimates put the amount of feather waste generated by the poultry industry between 2 billion and 3 billion lb per year. Getting rid of those feathers is more difficult than, say, making a few million feather dusters. The feathers are either burned, buried, or ground up into feather meal and fed to livestock--methods that are costly and controversial.

Several plucky chemists and chemical engineers are using these cast-off feathers to make all manner of products, from biodegradable plastic containers to hurricane-proof housing. At the American Chemical Society national meeting in Philadelphia, three of these scientists gave attendees a sample of their work during the "Nonfood Applications of Proteinaceous Renewable Materials" symposium sponsored by the Division of Cellulose & Renewable Materials.


Chicken feathers are made mostly of keratin, a protein also found in hair, hoofs, horns, and wool. Justin R. Barone, one of the symposium's presenters and a research scientist at the Department of Agriculture's Environmental Quality Laboratory in Beltsville, Md., explained that, relative to other proteins, keratin has a high cysteine concentration. The sulfur atoms in the cysteine residues tend to cross-link with one another, and this makes the protein tough, strong, and lightweight.

"Keratin from chicken feathers is robust like wool, but still relatively processable," Barone said. He and his USDA colleague Walter F. Schmidt have found that the material is ideal for strengthening composites. Because the keratin is naturally lightweight, it adds reinforcement to the composites without adding weight.

Barone uses conventional processing techniques to make these composites. Because chicken feathers are fairly inexpensive, he reckons that they could be cost-competitive with materials such as fiberglass and, consequently, ideal for automotive uses.

The primary cost of using chicken feathers comes from cleaning and sanitizing the feathers and stripping the thin feather fibers away from the quill. Both the fibers and the quill contain keratin, but scientists have primarily used the feather fibers, which are smaller and have a characteristic hollow tube structure.

FEATHER FIBERS Keratin in chicken feather fibers, seen in this scanning electron micrograph, forms strong, hollow tubes with a characteristic shape.
BIRD IN A WIRE Chicken feather microchip, printed by using a semiconductor fabrication technique.

USING ONLY the fibers creates feather waste because the quill portion, which accounts for about half of the feather by weight, still needs to be disposed of. For his latest project--creating biodegradable films out of chicken feathers--Barone gets around this problem by using the entire feather as a raw material.

To make his feather-based films, Barone grinds up the whole feather. Because he only needs the keratin protein and not the fibrous structure, it doesn't matter if the keratin comes from the feather's fibers or its quill. Not only does this eliminate feather waste, but, as Barone pointed out, it also saves the cost of separating the quill and fibers.

Barone can think of a number of applications for his feather films, but using them as mulching films appears particularly promising. Farmers and gardeners often use petroleum-based polymer films to prevent weeds from choking out certain crops and flowers. When the growing season is finished, before the land can be tilled, these films have to be pulled up by hand so that they aren't ground into the soil. The process is tedious and usually costs a lot in labor.

"THERE'S A LARGE impetus to make these films biodegradable," Barone explained. Unlike petroleum-based films, feather-based films would not need to be removed. Instead, they could be chopped up and turned into the ground, providing another nitrogen source for the soil.

Because the poultry industry makes only a few pennies in profit for every pound of chicken it produces, Barone said he tries to be conscious of costs. The industry is unlikely to invest in anything that will require new processes or equipment, so he makes a point of utilizing commonly used processing methods.

That point of view is shared by Jay-lin Jane, a professor at Iowa State University's department of food science and human nutrition in Ames, and Perminus M. Mungara, a research scientist in Jane's lab who spoke at the symposium.

Using conventional plastic processing techniques, such as extrusion, injection molding, and blow molding, Mungara and Jane transform powdered feather meal into biodegradable plastic. Typically, they blend the feather meal with soy protein and biodegradable polyesters using cyclohexanedimethanol, glycerol, or a combination of the two chemicals as plasticizers.

Mungara and Jane said that the keratin protein's chemical structure is hydrophobic and roughly as tough as synthetic materials, making it a good raw material for biodegradable plastics. Furthermore, Mungara and Jane reported that by tweaking the ingredients in the blend, they can vary the feather-based plastic's tensile strength, water resistance, flexibility, and lifetime.

Although the work is in the early stages of development, Mungara and Jane have already made prototype plastic containers with the feather-based blends. They report that the containers exhibit superior moisture resistance and degrade naturally.

With growing fears over diseases such as bovine spongiform encephalopathy, or mad cow disease, using animal waste in animal feed is becoming increasingly unpopular. Mungara and Jane think this trend will increase interest in alternative uses for feather meal. "I think it will be more valuable to use feathers as plastic," Jane commented. "It doesn't really provide much nutrition, and the nature of this polymer has more value."

Richard P. Wool, a chemical engineering professor at the University of Delaware, has been transforming chicken-feather fibers into useful materials for years. At the symposium, he spoke about several feather-based projects that he has been developing along with coworkers Chang K. Hong and Christopher W. McChalicher.

Within the past few years, Wool has gained fame by making circuit boards using chicken-feather keratin fibers and soybean resin. Both the Washington Post and Discover have reported on the project.

Although it's probably his most well-known work, Wool confessed that it did not begin as a completely serious exercise. Rather, the project was hatched as an exhibit for Delaware's state fair. Looking to highlight Delaware's two most bountiful agricultural resources, Wool and his colleagues decided to make a computer circuit board using soybeans and chicken feathers.

Wool already had extensive experience making resins out of soybean oils. Work in his lab led to John Deere's line of tractors made of soy-based materials. Computer circuit boards, however, require different properties than tractors.

Wool wanted a material that was strong and lightweight and had a lot of air in it. That's because airy materials tend to have low dielectric constants. The lower the dielectric constant of the circuit board, the faster electrons move on metal circuits printed on the material.

FEATHERWEIGHT These fluffy feather fibers are strong, lightweight, and absorbent.

It was also important to pick material with a relatively low coefficient of thermal expansion, otherwise the circuits could degrade while in use. Choosing keratin fibers from feathers was a guess, Wool admitted, "but a very calculated, educated guess."

The chicken-feather circuit was a hit at the fair. Wool said he was even approached by a representative from Tyson Foods who offered to give him 2 billion lb of chicken feathers. He declined the offer. Two billion lb of chicken feathers, Wool joked, is probably enough to cover the entire state of Delaware in a monolayer of feathers.

Wool's most ambitious feather-based project is to build hurricane-resistant houses out of keratin fiber-based materials. His group has made inexpensive, lightweight composites suitable for high-volume applications by combining cellulose fibers derived from wastepaper and cardboard with chicken feathers infused with soy resin. Using this composite as roofing material, Wool and coworkers built a prototype house that could withstand a hurricane's high winds.

FLIGHT OF FANCY Mungara (left) and Jane turn feather meal into biodegradable plastic.

TYPICAL ROOFS, Wool explained, are made of particleboards nailed together and covered with shingles. A hurricane can easily rip these boards off a house, leaving a gaping hole. Though costly, this damage is small compared to what happens when rain enters the house through this hole.

Wool's feather-based composite roof is one large piece that's molded on-site. Because of the roof's size, it takes a lot more force to pull the roofing away from the house. The project has piqued the interest of officials in both China and India.

Not one to keep all of his eggs in one basket, Wool has yet another project--carbonizing chicken-feather fibers. By pyrolyzing keratin fibers in an oxygen-free environment, he has managed to turn them into a material that is very similar to graphite fibers.

The pyrolysis shrinks the length and diameter of the keratin fibers, reducing the amount of protein in them by about 80%. However, the fibers retain their characteristic hollow shape. "This could provide a new source of unusual, lightweight, high-performance, low-cost fibers for composites," Wool said.

The symposium's scientists acknowledged that getting their products to fly won't be easy. They need support from the poultry industry along with interest from manufacturers. But considering the myriad products these researchers have already created, you'd have to be a birdbrain not to see the chicken feather's potential.

Chemists In The Henhouse

Everything pictured here is made from processed chicken feathers. Cross-section (left) and segment (top right) of hurricane-resistant roofing from Richard P. Wool's laboratory at the University of Delaware is also composed of wastepaper and soy resin (top right, foreground). Biodegradable plates (bottom right) by Iowa State University's Jay-lin Jane and Perminus M. Mungara are made using conventional plastic processing techniques .







  Chemical & Engineering News
ISSN 0009-2347
Copyright © 2004

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