Detroit's automakers are finding new uses for worn-out jeans, discarded plastic bottles and manufacturing rubbish -- they're recycling them for use in new vehicle parts.

With the rage over going green hitting the marketplace, auto companies are looking for ways to make their vehicles more sustainable, not just under the hood but behind the wheel.

They're incorporating more recycled materials into interiors, upholstery and moldings, and partnering with suppliers to develop new bio-based products to replace manmade plastics.

Aside from the feel-good benefits of using eco-friendly materials, automakers also see some cost savings in finding greener alternatives for plastics, fibers and moldings -- although not always.

And getting sustainable materials to perform like their highly durable manmade counterparts isn't easy and often requires more effort on the automaker's part to find a suitable substitute.

But for many auto companies, it's worth the effort to up their showroom cred with the green-living set.

"If we have two parts -- one is recycled, the other one is virgin -- and they perform and cost the same, why wouldn't you use the recycled one?," said Lora Herron, a materials engineer for General Motors Co. who has been heading up the company's efforts to green its materials.

Last year 9 percent of all recycled milk cartons, laundry detergent bottles and other materials made out of high-density polyethylene were used in automotive parts in the U.S., according to the Association of Post-consumer Plastics Recyclers. A decade ago, that percentage was "negligible," said David Cornell, the association's technical director.

At GM, materials engineers have turned recycled carpet into door handle brackets and stuffed shredded denim in linings and in crevices to dampen noise. In the 2010 Buick LaCrosse, the automaker is using discarded packaging cardboard from its Marion Stamping Plant in Indiana as acoustic ceiling panels. It also uses kenaf -- a bamboo-like plant -- for ceiling support and acoustics in some of its vehicles.

Herron estimates about 5 percent to 10 percent of plastics in GM vehicles are made of recycled content, a figure GM has strived to "ramp up" the last five years, she said. Chrysler Group LLC turns scrap yarn from carpet mills into durable plastic for use as an engine part in some vehicles.

At Ford Motor Co., many plastic parts used in shields and fender liners is made from recycled detergent bottles, tires and battery casings.

The suede-like seat fabrics in its 2010 Ford Taurus SHO and Lincoln MKZ are made from recycled plastic soda bottles and yarn. In 2008, the company said its recycling efforts saved it $4 million to $5 million and diverted 25 million to 30 million pounds of plastic from landfills. Ford also is developing biodegradable plastics made from sugars in plants, like corn and switch grass, for use as automotive parts.

"We said hey, we have to do a little better than great gas millage," said Carol Kordich, Ford's lead sustainability designer. "So we started looking into the interior."

Likewise, foreign automakers are heeding the call. Toyota Motor Corp., said it would strive to make at least 60 percent of its interior vehicle parts out of plant-derived materials this year.

While automakers want to get greener to meet changing consumer tastes, the strategy does not come without challenges. Parts need to perform well but also stand up to the kind of wear-and-tear sustained by vehicles over time. This can be particular difficult with bio-materials, Herron said.

Motorists aren't likely to see any cars or trucks made out of recycled cans.

"Aluminum actually doesn't recycle that well (for auto parts), which is strange because we recycle cans," Herron said.