DELTA TOWNSHIP, Mich. — General Motors Corp. showed off its newest assembly plant last week, a "green" facility that collects rainwater from the roof to flush toilets and was built with one-fourth recycled materials.

The plant outside Lansing will make the Saturn Outlook, GMC Acadia and Buick Enclave crossover vehicles starting later this year. Officials, who billed the auto plant as the world's most environmentally friendly, estimated GM will spend $1 million a year less on energy than in a typical plant.

"This is not your ordinary auto-assembly plant," said Elizabeth Lowery, GM's vice president for environment and energy. The GM plant has a reflective roof to reduce heat absorption, cutting cooling costs. It also has 800 lights in the assembly area, half that in a typical plant.

About 80 percent of the waste generated during construction, or nearly 4,000 tons, was diverted from landfills. Rainwater is collected from the roof and used instead of potable water to flush toilets. Nonmanufacturing use of water is 45 percent lower than normal, saving 4.1 million gallons every year, GM said.

Overall, the 2.4 million-square-foot facility is expected to save more than 40 million gallons of water and 30 million kilowatt hours of electricity in its first 10 years of operation. About 3,000 workers will be there during full production of the crossovers, which have many of the attributes of sport utility vehicles but are built on a car platform.

GM isn't the only automaker that has gone green. At Ford Motor Co.'s Dearborn Truck Plant, a "living roof" helps heat and cool the building.

David Skiven, executive director of the GM Worldwide Facilities Group, said when officials first suggested using environmental design and construction at the Lansing-area plant, some thought it was a "little nuts."

But the result, he said, is part of the next generation of industrial buildings, proving that sustainable manufacturing facilities can be built and operated economically.