When Agriculture Secretary Tom Vilsack praised production operations at Metrolina Greenhouses after a tour Monday, he wasn’t just talking about the 90 million plants grown there annually.

He was complimenting the Huntersville-based business for depending on wood chips, instead of gas, to heat the 162-acre facility in the winter.

Through a federal grant and loan from the Obama administration, Metrolina Greenhouses built four wood-boiler heating units to produce the energy needed to keep plants warm. Plenty of that wood comes from Metrolina’s backyard, including downed trees from the I-485 completion project.

“I’m never, ever going to think of a greenhouse the same way again,” said Vilsack, visiting the area to promote the federal program that helps businesses establish energy-efficient practices.

The greenhouses complex includes other functions designed to limit waste, such as a water filtration system that cleans out flower petals and dirt, allowing hundreds of thousands of gallons to be reused. An “energy curtain” on the roof helps keep the sun out during the summer, and heat in during the winter.

Owner Art Van Wingerden said the business had already decided to do the boilers and the energy curtain systems, and were willing to pay for it. “We took advantage of a federal grant program that has been out there for years,” Van Wingerden said.

Vilsack said practices such as these illustrate how some North Carolina businesses are leaders in a “new rural economy” that’s using natural products to become less dependent on traditional energy. Since 2007, Metrolina Greenhouses has received federal money totaling more than $1 million toward its energy-efficient practices, according to the U.S. Department of Agriculture.

During his visit, Vilsack also announced a new round of grant recipients, including 31 North Carolina companies and individuals receiving a combined $217,046 through the Rural Energy for America Program. That’s part of the food, farm and jobs bill, which is set to expire this year and is being debated in Congress.

Vilsack said North Carolina has 90 companies registered with the U.S. Department of Agriculture that use bio-based practices that reuse products, reduce waste and contribute to this new economy. He said the bill is key to boosting the number of businesses using these practices, which would help add jobs and revitalize rural areas.

Bio-based research is turning out a number of innovations around the country, Vilsack said. Examples include converting elements of hog manure into asphalt, and corn cobs into plastic.

“Why wouldn’t we replicate nature... (so) there is no such thing as waste?” Vilsack said in a meeting with the Observer editorial board.

“We have enormous opportunities here,” he said, “particularly in rural areas, where we have this grand opportunity... to create new energy products.”

Among the new North Carolina grant recipients are farms and small-business operations. Their projects, receiving funding ranging from $1,500 to $20,000, include installing energy-conserving insulation and launching projects that depend on solar power.

Nationally, the Obama administration has awarded grants to 6,600 projects that reduce energy use, Vilsack said.