The nation’s largest farmer-owned cooperative, CHS Inc., acquired a large ethanol plant on Monday for $196 million — and said it wants to buy more.

CHS, based in Inver Grove Heights, purchased the Patriot Renewable Fuels ethanol plant in Annawan, Ill., 140 miles southwest of Chicago. Just a year ago, CHS acquired its first ethanol plant, also in Illinois.

The latest, $196 million deal won approval from 91 percent of the 200 investors, which included farmers and local business people, said Tim Wells, an investor and former banker who helped put together the original project. CHS declined to discuss the price.

“CHS saw the potential, and they offered to buy and there wasn’t a lot of resistance,” said Wells, who now is treasurer of Henry County, where the plant is located.

The plant can produce more than 120 million gallons of ethanol per year. The acquisition is part of the co-op’s strategy to expand into renewable fuel production. CHS has long marketed ethanol and has 1,400 mostly franchised Cenex gas stations that sell ethanol-blended motor fuel.

“We are looking for top-tier plants,” said Gary Anderson, CHS senior vice president for North America grain marketing and renewable fuels.

In an interview, Anderson didn’t say how many plants CHS wants to acquire. But he said the co-op is looking for operations with output of more than 100 million gallons per year, with good technology and in good corn-growing regions.

About 30 percent of the nation’s 211 ethanol plants are that size or bigger, according to Renewable Fuels Association data.

The Annawan plant was completed in 2008, after the Henry County Economic Development Partnership, a nonprofit group, funded a feasibility study and held town meetings for potential investors, said Kathleen Repass, director of the partnership.

Wells said the plant earned a record $54 million last year. A biodiesel production plant, also acquired by CHS, is under construction next to the plant and will process its byproduct industrial corn oil into motor fuel, Wells said.

Anderson said the ethanol plant’s 68 employees, including managers, will retain their jobs. The plant will be renamed CHS-Annawan, he said.

Last June, CHS acquired a 133-million-gallon-per-year plant in Rochelle, Ill. It was the first time CHS had taken on the role of full ownership and direct management in the ethanol industry.

Over the years, the co-op has twice entered, and exited, the ethanol business. In the 1980s, it co-owned a small ethanol plant in North Dakota, but in 1991 sold its stake. In 2006, CHS acquired 24 percent of US BioEnergy, which then owned four ethanol plants. But CHS wrote off $74 million of the investment after US BioEnergy merged with VeraSun, which went bankrupt in 2008.