Ever more companies are turning their attention to creating renewable products – such as adhesives and plastics – from the animal parts that cannot be sold on supermarket shelves, reports USA Today.

From plastics made from feather protein to diesel fuel made from fat to organic fertiliser made from poultry litter, the US's top meat producers are developing new uses and markets for the animal parts that humans will not eat, says Tom Cook, president of the National Renderers Association in Alexandria, Virginia.

For years, those parts have ended up in cosmetics, soap, pet food and animal feed. Now, meat companies are putting more resources into sustainability programmes, says Paul Rutledge of the American Meat Institute's sustainability committee.

At Clemson University, such products are being tested at the South Carolina school's Animal Co-Products Research & Education Center, says Center Director, Annel Greene.

Dr Greene says there are a number of uses for the leftover materials that have yet to be discovered. "It's fascinating to see everything that can be done."

Kathy Guillermo, vice president of laboratory investigations for People for the Ethical Treatment of Animals PETA), says many consumers would be surprised to learn the number of products with animal ingredients in them. She says rendered materials, which are fed to livestock and pets, could spread diseases.

"The last thing we need in this country is another use for the bodies of animals," she told USA Today.

Waste materials from meat processing are treated with special considerations at landfills because they produce strong odours and methane when decomposing, said Jeremy O'Brien, director of applied research for the Solid Waste Association of North America.

"Anytime you can reduce the amount of waste going into one, you're preserving a resource," Mr O'Brien said.

USA Today cites the following examples of projects underway:

• Tyson Foods is developing plastics, adhesives and non-woven materials from the keratin protein found in feathers, says Jeff Webster, the group vice president of the renewable products division. Someday, disposable babies' nappies (diapers) or hospital gowns could be made from the materials, he says.
  
  Tyson Foods is also involved in a joint venture with Syntroleum Corp. of Tulsa to build a renewable fuels plant in Baton Rouge. Webster says the plant, expected to be at full production next July, will convert beef tallow, pork lard, chicken fat and cooking grease into a synthetic diesel fuel. Because of the fuel's ultra-low emissions grade, it will be marketed to emission-cap markets, underground mining companies and the general aviation market.
  
  
• Perdue Farms collects poultry litter – a blend of manure and wood shavings – and converts it into organic fertilizer pellets to be sold to wholesalers, says Cathy Klein, vice president for co-product sales.
  
  
• Maple Leaf Foods of Toronto operates its own biodiesel plant near Montreal and uses a portion of the fuel it produces in its company trucks, says Todd Moser, vice president of alternative fuels.