DETROIT — From concept cars partially made of discarded soft-drink bottles to plant-based material used in seats and upholstery, automakers are looking at ways to make their vehicles more environmentally friendly.

While efforts to roll out more gas-saving hybrids, meet tougher fuel-economy standards and cut tailpipe emissions get much of the attention, what goes into making cars is another key part of efforts to green the auto industry.

"The whole issue around sustainability is not just about fuel economy," Mark Fields, Ford Motor Co.'s president for the Americas, said after unveiling the Lincoln MKT concept touring vehicle during media previews at the North American International Auto Show. "It's not just about lowering CO2 levels. It's being good stewards in the environment, and that means the materials that you use."

The Lincoln MKT, which partially is made of plastic bottles and polyester waste, underscores Ford's hope to commercialize greener materials and appeal to more environmentally minded drivers. It's part of increasing attention industrywide to the overall environmental impact of vehicles.

But unlike Toyota Motor Corp.'s gas-sipping hybrid Prius, which offers drivers instant recognition for buying an environmentally friendly vehicle, car bodies made out of recycled materials and interiors that feature plant-based fabrics aren't easily noticeable to buyers, if at all.

"It's an open question whether people are willing to pay more," said Jack Nerad, executive market analyst for Irvine, Calif.-based Kelley Blue Book, who noted such offerings typically come at a premium.

Taking steps to make vehicles more environmentally friendly is a given across the industry, auto analysts say. Aaron Bragman, an analyst with the consulting firm Global Insight in the Detroit suburb of Troy, said, "It's expected that you're making every single effort in every single line to be green."

At the show, which opened to the public Saturday, Honda Motor Co.'s FCX Clarity hydrogen fuel cell-powered car uses plant-based fabric for its interior. At the display for Daimler AG's Mercedes-Benz, the automaker highlights that some of its vehicles were awarded an environmental certification for factors including components made from recycled materials.

And during last week's press previews, Johnson Controls Inc. showed off its new Ecobond headliner — part of the interior roof of vehicles — that uses soy-based material and natural fibers instead of the traditional fiberglass. The Ecobond — made from fibers including hemp and flax — also cuts vehicle weight.

"This approach can help increase fuel economy and reduce carbon emissions," said Jeff Williams, group vice president for Johnson Controls. And it "is also easier to recycle at the end of the vehicle's useful life."

Johnson Controls sells a soy-based seat foam that it says is being used in 1.6 million vehicles a year for the 2008 model year. And Ford has a soy-based seat foam, which is on Ford's 2008 Mustang sports car, F-150 pickup and Expedition sport utility vehicle, as well as the Lincoln Navigator SUV.